Knowledge Base / Herbs
Herbs A to Z
What each herb is used for, what the research shows, and who should avoid it.
A practical guide to 37 herbs and botanicals. See the doses used in human studies, an honest rating of the evidence, common forms and the safety points that matter, then read our full guide for each herb. Natural does not mean risk-free: several herbs here interact with common medicines.
Quick reference
Compare daily needs, upper limits and common food sources at a glance.
| Herb | Main use | Studied dose | Evidence | Forms |
|---|---|---|---|---|
| Anamu | Immune, inflammation, pain support | 1,000–1,500 mg whole herb, 1–2 times daily (traditional, not trial-based) | Very limited | Capsules, dried leaf tea, cut root decoction, tincture |
| Ashwagandha | Stress, cortisol, sleep | 300–600 mg standardized root extract daily, often 300 mg twice | Moderate | Capsules (KSM-66, Sensoril extracts), root powder, tincture |
| Astragalus | Kidney support, immune tonic | 3–6 g dried root daily (3–6 capsules of 1000 mg) | Limited | Capsules, dried root decoction, standardized extract, granules |
| Bitter Melon | Blood sugar support | No standard dose established; capsules supply 1000 mg each | Moderate | Fresh fruit, juice, capsules, dried extract |
| Black Cohosh | Menopause hot flashes, night sweats | 40–80 mg standardized extract daily | Limited | Standardized extract, root capsules |
| Boswellia | Joint pain, osteoarthritis stiffness | 100–250 mg 30% AKBA extract, or 800–1600 mg resin | Moderate | Whole resin capsules, standardized extracts (AKBA); essential oil not equivalent |
| Burdock Root | Skin, digestion, antioxidant support | 1,000–1,100 mg dried root daily (label-based, not trial-based) | Very limited | Capsules, powder, dried slices, tincture, tea |
| Cat's Claw | Joint comfort, immune support | 1000–3000 mg bark capsules daily, or 1–3 mL tincture | Limited | Bark capsules, tincture, purified extract, bark decoction |
| Ceylon Cinnamon | Blood sugar, low-coumarin cinnamon | 1–2 g powder or one 1000 mg capsule daily | Limited | Powder, sticks (quills), capsules, extracts |
| Chanca Piedra | Kidney stones, after lithotripsy | 2 g daily for at least 3 months (trial dose) | Limited | Capsules, tea |
| Cilantro | Antioxidant, digestive, metabolic support | 250–1000 mg capsules daily (label-based, not trial-tested) | Very limited | Capsules, tincture, powder |
| Damiana | Traditional aphrodisiac, tea | No standard dose established (label: 1 capsule of 1000 mg) | Very limited | Capsules, tea |
| Dandelion Root | Traditional bitter for digestion | No standard dose established; 1 study used about 2.1 g | Very limited | Capsules, tincture, roasted tea |
| Echinacea | Immune support, common cold | No standard dose established; short 7–10 day courses | Limited | Capsules, tinctures, teas |
| Evening Primrose Oil | GLA oil; eczema, breast pain studied | No standard dose; trials used well above 1 softgel (1300 mg) daily | Limited | Softgels |
| Fenugreek | Blood sugar, milk supply, testosterone | No standard dose established; trials used 600–1800 mg extract daily | Moderate | Capsules, extract, ground or soaked seeds, tea |
| Feverfew | Migraine frequency | 6.25 mg CO2 extract 3 times daily, not 1000 mg herb | Limited | Capsules (dried herb), standardized extract, tea, fresh leaves |
| Ginkgo Biloba | Cognition, vertigo, anxiety | 120–240 mg standardized EGb 761 extract daily, divided | Moderate | Standardized extract capsules, leaf capsules |
| Hibiscus | Blood pressure | 3 cups (240 mL each) of brewed tea daily for 6 weeks | Moderate | Tea, capsules |
| Holy Basil (Tulsi) | Everyday stress, sleep, blood sugar | Trial extracts: 125 mg twice daily to 1,200 mg daily | Limited | Capsules, tea, tincture |
| Horse Chestnut | Leg vein swelling, heaviness, aching | 50 mg aescin twice daily, from 16–20% aescin extract | Moderate | Standardized capsules, topical cream |
| Konjac (Glucomannan) | Cholesterol, blood sugar, regularity | 1.33 g with water before each of 3 meals (trial) | Moderate | Capsules; also eaten as konjac jelly and noodles |
| Maca Root | Sexual desire, menopausal symptoms | 1.5–3 g dried root daily, with food | Limited | Powder, capsules, gelatinized, raw |
| Mastic Gum | Indigestion (functional dyspepsia), H. pylori | 350 mg 3 times daily (trial); EMA: 0.5–1 g twice daily | Limited | Capsules, chewing gum, resin tears |
| Milk Thistle | Liver support, NAFLD liver enzymes | 140–420 mg standardized silymarin daily, split with meals | Moderate | Standardized capsules, phytosome capsules, tea, tincture, seed powder |
| Moringa | Leaf nutrition, blood sugar | 1–2 g leaf powder daily; one trial used 2.4 g | Very limited | Powder, capsules |
| Mullein | Traditional throat, chest, skin use | No standard dose established | Very limited | Capsules, strained tea |
| Oregano Oil | Antimicrobial, gut and immune support | No standard dose established; labels suggest 150–450 mg daily for 2–4 weeks | Very limited | Capsules (incl. enteric-coated), softgels, liquid oil, tincture |
| Passionflower | Anxiety before procedures, sleep | 500 mg single dose, 90 minutes before surgery (trial) | Limited | Capsules, tincture, tea |
| Rhodiola | Stress-related fatigue, attention | No established dose; one trial used 400 mg daily | Limited | Standardized extract capsules, root powder, tea, multi-herb blends |
| Saw Palmetto | Urinary symptoms of mild BPH | 320 mg standardized berry extract daily | Limited | Berry extract capsules, multi-herb prostate formulas |
| Slippery Elm | Soothing sore throat and gut | Lozenge with 10–15 percent elm bark, every 2 hours as needed | Very limited | Lozenges, capsules, powder, tea or warm drink |
| St. John's Wort | Mild to moderate low mood | 900 mg standardized extract daily, as 300 mg 3 times | Moderate | Standardized extract, dried herb capsules |
| Stinging Nettle | Prostate (root); allergies, joints (leaf) | Root: 459 mg extract daily; leaf: 500 mg extract every 8 hours | Limited | Leaf capsules, tea, root extract, cooked leaves, fresh leaf on skin |
| Tongkat Ali | Testosterone, libido, stress | 200–400 mg standardized root extract daily | Limited | Standardized root extract capsules |
| Turmeric | Inflammation, knee joint pain | 500–2000 mg curcumin extract daily, with an absorption enhancer | Moderate | Root powder capsules, standardized curcumin extract, piperine or phospholipid forms |
| Yohimbe | Erectile function, fat loss | No established safe dose for the bark; trials used isolated yohimbine | Limited | Whole-bark capsules, yohimbine HCL (pharmaceutical) |
Evidence ratings: Moderate = several human randomized trials or a meta-analysis support a specific use; Limited = a few small human trials; Very limited = mostly lab, animal or traditional use. Studied doses are the amounts used in human trials described in our guides; product labels and plain dried herb can differ from standardized extracts.
Herbs are not a substitute for diagnosis or prescribed treatment. If you take prescription medicine, are pregnant or breastfeeding, or have surgery planned, check with your doctor or pharmacist first.
Explore the herbs
What it is used for, the dose used in studies, how strong the evidence is, and who should avoid it.
Anamu
Petiveria alliacea, Whole herb (leaf and root) · Very limited evidence
Traditionally used for immune, inflammation and pain support; research is mostly lab and animal work on immune modulation and blood sugar.
Studied dose: 1,000–1,500 mg whole herb, 1–2 times daily (traditional, not trial-based)|Evidence: 40+ compounds, 0 large human trials; 1 unreported trial protocol
Forms: Capsules, dried leaf tea, cut root decoction, tincture
Who should avoid: Avoid in pregnancy and breastfeeding; caution with blood thinners, diabetes or blood pressure drugs; stop at least 2 weeks before surgery.
Safety: May stimulate the uterus, so never use in pregnancy; its coumarins may also raise bleeding risk with warfarin and other blood thinners.
Ashwagandha
Withania somnifera, Root · Moderate evidence
An Ayurvedic adaptogen used for stress and sleep; trials looked at cortisol, sleep quality, muscle strength and memory.
Studied dose: 300–600 mg standardized root extract daily, often 300 mg twice|Evidence: Several double-blind trials (50–64 adults, 8–10 weeks); cortisol fell 27.9%
Forms: Capsules (KSM-66, Sensoril extracts), root powder, tincture
Who should avoid: Pregnancy and breastfeeding; hyperthyroidism, Hashimoto's or other autoimmune disease; liver disease; people on thyroid, blood pressure, sedative or immunosuppressant drugs.
Safety: Rare liver injury: a 2020 case series reported 10 cases and LiverTox rates it 'Probable'; stop and seek care if jaundice or dark urine appears.
Astragalus
Astragalus membranaceus, Root · Limited evidence
A Chinese tonic root used for immune and kidney support; research mostly measured kidney markers, largely with injected rather than oral astragalus.
Studied dose: 3–6 g dried root daily (3–6 capsules of 1000 mg)|Evidence: Low-quality kidney data, mostly injection; just 4 oral trials, 236 participants
Forms: Capsules, dried root decoction, standardized extract, granules
Who should avoid: Transplant recipients and people on immunosuppressants; autoimmune disease; pregnancy and breastfeeding; kidney disease under care without nephrologist input.
Safety: Stimulates immune activity, so it may counter immunosuppressants such as cyclosporine and tacrolimus; people on lithium or diuretics should check with a pharmacist.
Bitter Melon
Momordica charantia, Fruit · Moderate evidence
Eaten as a vegetable and taken as a supplement for blood sugar; trials measured fasting glucose, HbA1c and insulin resistance.
Studied dose: No standard dose established; capsules supply 1000 mg each|Evidence: 25-trial 2025 meta-analysis positive; 2012 Cochrane found no significant effect
Forms: Fresh fruit, juice, capsules, dried extract
Who should avoid: Pregnancy; people on insulin or a sulfonylurea without clinician input; children must never be given the red seed arils.
Safety: May add to insulin or sulfonylurea effects, so watch for low blood sugar; the red seed arils are linked with harm in children.
Black Cohosh
Actaea racemosa (formerly Cimicifuga racemosa), Root · Limited evidence
Used for menopause symptoms, mainly hot flashes and night sweats; trials tested standardized root extract over 4 to 8 weeks.
Studied dose: 40–80 mg standardized extract daily|Evidence: 30+ trials with mixed results; reviews disagree on the size of the benefit
Forms: Standardized extract, root capsules
Who should avoid: Pregnancy and breastfeeding, liver disease, and hormone-sensitive cancers: ask your doctor first.
Safety: Rare cases of liver injury have been reported. Stop and see a doctor if you notice dark urine, yellow skin or unusual tiredness.
Boswellia
Boswellia serrata, Gum resin · Moderate evidence
Used for joint pain and stiffness; knee osteoarthritis trials found short-term reductions in pain and stiffness, not lasting long-term benefit.
Studied dose: 100–250 mg 30% AKBA extract, or 800–1600 mg resin|Evidence: 7 trials, 545 patients: less pain and stiffness, short term only
Forms: Whole resin capsules, standardized extracts (AKBA); essential oil not equivalent
Who should avoid: Pregnancy and breastfeeding; people on anticoagulants or immune-modifying drugs; liver disease; all need clinician input first.
Safety: Mild digestive upset (nausea, reflux, loose stools) is most common; anyone on anticoagulants or immune drugs should talk to a clinician first.
Burdock Root
Arctium lappa, Root (taproot) · Very limited evidence
Traditionally used for skin, digestion and gentle cleansing; research looked at its inulin fiber and antioxidants, mostly in lab and animal studies.
Studied dose: 1,000–1,100 mg dried root daily (label-based, not trial-based)|Evidence: Only 2 small human trials; most findings from cell and animal studies
Forms: Capsules, powder, dried slices, tincture, tea
Who should avoid: Pregnancy and breastfeeding; ragweed or other Asteraceae allergy; dehydration; people on diuretics, diabetes medicine or blood thinners without a doctor.
Safety: Sourcing matters: wild burdock resembles belladonna, and past poisonings came from tea contaminated with an atropine-like compound.
Cat's Claw
Uncaria tomentosa or Uncaria guianensis, Inner bark · Limited evidence
Used for joint and immune complaints; 2 small trials looked at knee osteoarthritis and rheumatoid arthritis pain with specific preparations.
Studied dose: 1000–3000 mg bark capsules daily, or 1–3 mL tincture|Evidence: 2 small trials: 45 knee osteoarthritis and 40 rheumatoid arthritis patients
Forms: Bark capsules, tincture, purified extract, bark decoction
Who should avoid: Transplant recipients, immunosuppressant or biologic users, autoimmune disease, pregnancy or breastfeeding, and anyone within 2 weeks of surgery.
Safety: Immune-active, so it may counter immunosuppressants such as cyclosporine and tacrolimus; also check blood pressure drugs, anticoagulants and CYP3A4-processed drugs.
Ceylon Cinnamon
Cinnamomum verum, Inner bark · Limited evidence
Used as a low-coumarin spice and supplement; research looked at modest effects on blood sugar, lipids and antioxidant markers.
Studied dose: 1–2 g powder or one 1000 mg capsule daily|Evidence: 10-plus trials, mostly cassia; modest, mixed blood-sugar effects
Forms: Powder, sticks (quills), capsules, extracts
Who should avoid: People on warfarin, other anticoagulants or diabetes medication; liver disease; pregnancy or breastfeeding; anyone within 2 weeks of surgery.
Safety: May add to diabetes medications and lower blood sugar further; its trace coumarin adds theoretical bleeding risk with warfarin.
Chanca Piedra
Phyllanthus niruri, Whole herb (leaves and stems) · Limited evidence
Used traditionally for urinary stones; research looked at stone clearance after shock wave lithotripsy and stone size, with modest, mostly non-significant results.
Studied dose: 2 g daily for at least 3 months (trial dose)|Evidence: Only 2 human trials; main 150-patient trial not significant overall (p = 0.48)
Forms: Capsules, tea
Who should avoid: Pregnancy or trying to conceive; existing kidney disease; people on diuretics, blood pressure, diabetes medication or anticoagulants should ask first.
Safety: No side effects were recorded in the 150-patient trial; check with a pharmacist first if you take diuretics, blood pressure, diabetes medication or anticoagulants.
Cilantro
Coriandrum sativum, Leaves and seeds · Very limited evidence
Used for antioxidant, digestive and metabolic support and heavy-metal detox routines; research is mostly lab and animal work, plus one human herbal-formula IBS study.
Studied dose: 250–1000 mg capsules daily (label-based, not trial-tested)|Evidence: Mostly rodent and lab data; one open-label human IBS formula study
Forms: Capsules, tincture, powder
Who should avoid: Pregnancy and breastfeeding (concentrated extracts), Apiaceae allergy (carrot, celery), children without guidance; diabetes or blood-pressure medication users should ask first.
Safety: May add to the glucose-lowering effect of diabetes medication, so monitor blood sugar for the first 2 weeks; mild digestive upset affects under 5% of users.
Damiana
Turnera diffusa, Leaf · Very limited evidence
Used traditionally as an aphrodisiac and tea; most research is in chemical, cell or animal assays, and both human studies used multi-ingredient formulas.
Studied dose: No standard dose established (label: 1 capsule of 1000 mg)|Evidence: 12 reported activities tested mostly in cells or animals; 0 herb-alone human trials
Forms: Capsules, tea
Who should avoid: Pregnancy or planning pregnancy, diabetes or glucose-lowering medication, liver disease; do not smoke or vape the leaf.
Safety: Avoid in pregnancy because Turnera species are traditionally used as abortives; ask first if on glucose-lowering medication, since antidiabetic activity is reported in animals.
Dandelion Root
Taraxacum officinale, Root · Very limited evidence
Taken as a traditional bitter for mild digestive complaints; liver and cancer claims rest on animal and cell studies, not human root trials.
Studied dose: No standard dose established; 1 study used about 2.1 g|Evidence: 1 human root-alone study (no extra urine); liver data from mice, rats
Forms: Capsules, tincture, roasted tea
Who should avoid: Daisy-family (ragweed) allergy, gallstones, blocked bile duct or liver disease, kidney or heart failure, diabetes, pregnancy, breastfeeding; lithium or diuretic users ask first.
Safety: Check with a clinician if you take lithium, a prescription diuretic or a potassium-raising medicine; allergic reactions are possible in ragweed-sensitive people.
Echinacea
Echinacea purpurea (also E. angustifolia, E. pallida), Root and aerial herb · Limited evidence
Taken mainly for immune and cold support at the first sign of symptoms; cold trials and reviews show mixed, modest results.
Studied dose: No standard dose established; short 7–10 day courses|Evidence: Mixed: 2014 Cochrane found weak prevention benefit; 2019 review modest signal
Forms: Capsules, tinctures, teas
Who should avoid: Asteraceae allergy (ragweed, daisies, marigolds, chrysanthemums); ask a clinician if pregnant, breastfeeding, giving to children or on immune-modulating medication.
Safety: Allergic reactions in people sensitive to ragweed or daisies, with rare anaphylaxis reported; other side effects are usually mild, such as stomach upset or rash.
Evening Primrose Oil
Oenothera biennis, Seed oil · Limited evidence
A seed oil supplying gamma-linolenic acid, studied mostly for eczema and PMS without benefit; some signals for breast pain, hot flashes and skin hydration.
Studied dose: No standard dose; trials used well above 1 softgel (1300 mg) daily|Evidence: Cochrane: 27 eczema studies, 1596 people, no significant benefit
Forms: Softgels
Who should avoid: Anticoagulant or antiplatelet users, seizure disorders or phenothiazine medicines, and pregnancy unless discussed with the maternity team (never self-use to start labor).
Safety: Possible bleeding risk with anticoagulant medicines such as warfarin; otherwise an occasional upset stomach is the usual effect.
Fenugreek
Trigonella foenum-graecum, Seed · Moderate evidence
Used for blood sugar, breastfeeding milk supply and testosterone; blood sugar has the best human evidence, while milk-supply and testosterone results are weak.
Studied dose: No standard dose established; trials used 600–1800 mg extract daily|Evidence: Blood sugar: meta-analysis of 10 studies, 706 people; other uses weaker
Forms: Capsules, extract, ground or soaked seeds, tea
Who should avoid: Pregnancy, legume allergy, surgery within 2 weeks, and diabetes medication users without telling their clinician.
Safety: May add to the effect of diabetes medication such as insulin or a sulfonylurea; mild digestive effects are the usual complaint.
Feverfew
Tanacetum parthenium, Leaf (dried herb) · Limited evidence
Studied for reducing how often migraines occur; the best trial found 0.6 fewer attacks a month than placebo, a modest difference.
Studied dose: 6.25 mg CO2 extract 3 times daily, not 1000 mg herb|Evidence: Mixed: 9 trials pooled, modest drop; Cochrane could not pool 6
Forms: Capsules (dried herb), standardized extract, tea, fresh leaves
Who should avoid: Pregnancy or planning pregnancy, anticoagulant or antiplatelet users, and anyone allergic to ragweed, chrysanthemums, marigolds or daisies.
Safety: Avoid with warfarin, other anticoagulants or antiplatelet medicines; chewing fresh leaves is associated with mouth ulceration.
Ginkgo Biloba
Ginkgo biloba, Leaf (standardized extract) · Moderate evidence
Used for memory, circulation, tinnitus and vertigo; large trials found no dementia prevention, with modest signals for existing cognitive impairment, vertigo and anxiety.
Studied dose: 120–240 mg standardized EGb 761 extract daily, divided|Evidence: No dementia prevention in 5,900+ adults; modest signals in existing impairment
Forms: Standardized extract capsules, leaf capsules
Who should avoid: Blood thinner or antiplatelet users, seizure disorders, surgery within 2 weeks, pregnancy and breastfeeding; never eat raw or roasted seeds.
Safety: Raises bleeding risk with anticoagulants, antiplatelets and NSAIDs by inhibiting platelet-activating factor; stop 1-2 weeks before surgery or dental procedures.
Hibiscus
Hibiscus sabdariffa, Calyx (dried) · Moderate evidence
Brewed as a tart red tea; human research mainly looked at modest blood pressure lowering, while weight and cholesterol trials showed little or mixed results.
Studied dose: 3 cups (240 mL each) of brewed tea daily for 6 weeks|Evidence: 5 meta-analyses agree on a systolic fall; Cochrane rated certainty very low
Forms: Tea, capsules
Who should avoid: Pregnancy or breastfeeding, kidney disease or stones, low blood pressure; people on blood pressure drugs, diuretics, chloroquine or glucose-lowering medicine.
Safety: May add to blood pressure drugs or diuretics; one study found chloroquine blood levels cut by about 71%.
Holy Basil (Tulsi)
Ocimum tenuiflorum (also listed as Ocimum sanctum), Leaf and stem · Limited evidence
Sold as an adaptogen for everyday stress; small human trials looked at self-rated stress, hair cortisol, sleep scores and fasting blood sugar.
Studied dose: Trial extracts: 125 mg twice daily to 1,200 mg daily|Evidence: Only 4 of 21 tagged trials tested tulsi alone; all small, short
Forms: Capsules, tea, tincture
Who should avoid: Pregnancy, breastfeeding or trying to conceive; thyroid conditions or medication; glucose-lowering medicine; surgery within 2 weeks.
Safety: May add to glucose-lowering medicines, based on a 1996 trial; fertility and thyroid cautions come only from animal studies never repeated in people.
Horse Chestnut
Aesculus hippocastanum, Seed (standardized extract) · Moderate evidence
Standardized seed extract is used for leg heaviness, aching and swelling from weak leg veins; trials compared it with placebo and compression stockings.
Studied dose: 50 mg aescin twice daily, from 16–20% aescin extract|Evidence: Cochrane review of 17 trials (1,051 people): less leg pain and swelling
Forms: Standardized capsules, topical cream
Who should avoid: Pregnancy, breastfeeding, bleeding disorders, kidney or liver disease, within 2 weeks of surgery, children under 12; never eat raw seeds.
Safety: Aescin can add to bleeding risk with anticoagulants, antiplatelets or daily aspirin. Raw seeds contain toxic esculin; use only standardized extract.
Konjac (Glucomannan)
Amorphophallus konjac, Root · Moderate evidence
Sold for appetite and weight, but the best trial found no weight effect; studies support lower LDL cholesterol and fasting glucose.
Studied dose: 1.33 g with water before each of 3 meals (trial)|Evidence: 12 studies (370 people) lowered LDL; a 53-person weight trial found nothing
Forms: Capsules; also eaten as konjac jelly and noodles
Who should avoid: Anyone with swallowing difficulty, esophageal narrowing or previous bowel obstruction; konjac jelly mini-cups should not be given to young children.
Safety: The fiber gels in water: take each capsule with a full glass of water and do not lie down soon after; chest pain or trouble swallowing is an emergency.
Maca Root
Lepidium meyenii, Root (dried hypocotyl) · Limited evidence
Andean root vegetable taken for libido, mood and menopausal comfort; small trials looked at sexual desire and found no testosterone change in men.
Studied dose: 1.5–3 g dried root daily, with food|Evidence: Several small randomized trials; modest libido benefit over 6 to 12 weeks
Forms: Powder, capsules, gelatinized, raw
Who should avoid: People with thyroid concerns (goitrogen caution), hormone-sensitive conditions, or who are pregnant or breastfeeding should consult a clinician first.
Safety: Generally well tolerated; it contains glucosinolates, so people with thyroid concerns should note the goitrogen caution, which cooking or gelatinizing lowers.
Mastic Gum
Pistacia lentiscus var. chia, Resin · Limited evidence
Greek shrub resin used for indigestion; trials found dyspepsia relief versus placebo but weak effects against H. pylori in people.
Studied dose: 350 mg 3 times daily (trial); EMA: 0.5–1 g twice daily|Evidence: One 148-patient trial: 77% improved vs 40% on placebo
Forms: Capsules, chewing gum, resin tears
Who should avoid: Pregnancy, breastfeeding, under 18; allergy to pistachio, cashew or Mastisol; a positive H. pylori test or alarm symptoms need a doctor.
Safety: Well tolerated in trials; the real caution is allergy, since mastic belongs to the cashew and pistachio family.
Milk Thistle
Silybum marianum, Seed · Moderate evidence
Taken for liver support; trials looked at liver enzymes in fatty liver disease, blood sugar markers, and liver stress during chemotherapy.
Studied dose: 140–420 mg standardized silymarin daily, split with meals|Evidence: 2024 meta-analysis of RCTs: lower ALT and AST in NAFLD
Forms: Standardized capsules, phytosome capsules, tea, tincture, seed powder
Who should avoid: Pregnancy, breastfeeding, hormone-sensitive cancers, Asteraceae (ragweed) allergy, children without supervision, active liver disease without a hepatologist.
Safety: Interacts with at least 10 drug classes, notably CYP3A4 substrates and antidiabetics (additive blood sugar lowering); check with a prescriber first.
Moringa
Moringa oleifera, Leaf · Very limited evidence
Dried leaf taken as a green food supplement; human trials on blood sugar and cardiometabolic markers found no consistent benefit.
Studied dose: 1–2 g leaf powder daily; one trial used 2.4 g|Evidence: 2025 meta-analysis of 9 human trials: no consistent benefit, very low certainty
Forms: Powder, capsules
Who should avoid: Pregnancy, trying to conceive, breastfeeding; glucose-lowering, thyroid or blood pressure medicine; high clot risk; prior reaction to moringa.
Safety: Possible interactions with glucose, blood pressure and thyroid medicines; CDC investigated 4 Salmonella outbreaks linked to moringa products since 2025.
Mullein
Verbascum thapsus, Leaf · Very limited evidence
Traditionally used for the throat, chest and skin; no human trial has tested mullein taken by mouth for breathing.
Studied dose: No standard dose established|Evidence: 148 records, 3 trials; 0 tested oral use for breathing
Forms: Capsules, strained tea
Who should avoid: Pregnancy and breastfeeding; anyone with COPD, asthma or emphysema, new or worsening breathlessness, or a cough beyond 3 weeks should see a clinician.
Safety: Do not forage it: a first-year mullein rosette resembles foxglove, which is cardiotoxic. Leaf hairs can scratch the throat, so strain tea.
Oregano Oil
Origanum vulgare, Leaf essential oil (steam-distilled) · Very limited evidence
Concentrated carvacrol-rich oil taken for gut, sinus and immune support; the research described is mostly lab and test-tube work.
Studied dose: No standard dose established; labels suggest 150–450 mg daily for 2–4 weeks|Evidence: Mostly lab and animal studies; few human trials of oregano oil alone
Forms: Capsules (incl. enteric-coated), softgels, liquid oil, tincture
Who should avoid: Pregnancy and breastfeeding, and people allergic to oregano, thyme, basil or other mint-family plants.
Safety: Concentrated oil can irritate the mouth and stomach; use short courses of 2-4 weeks rather than months of continuous use.
Passionflower
Passiflora incarnata, Aerial parts · Limited evidence
Used as a calming herb for anxiety and sleep; most trials tested one dose before surgery or a dental extraction.
Studied dose: 500 mg single dose, 90 minutes before surgery (trial)|Evidence: About 11 single-herb trials; 7 tested 1 pre-procedure dose
Forms: Capsules, tincture, tea
Who should avoid: Pregnancy, trying to conceive, breastfeeding; people using alcohol, sedatives, opioids or sedating herbs; sedation procedures within 2 weeks; driving.
Safety: May add to alcohol and sedatives such as benzodiazepines, sleeping pills and opioids; NCCIH lists drowsiness, dizziness and confusion.
Rhodiola
Rhodiola rosea, Root · Limited evidence
People take it for stress-related fatigue and focus; small trials looked at burnout scores, attention and the cortisol response to waking.
Studied dose: No established dose; one trial used 400 mg daily|Evidence: Small trials of 10–80 people; a review of 11 trials found contradictory results
Forms: Standardized extract capsules, root powder, tea, multi-herb blends
Who should avoid: Pregnancy and breastfeeding; depression, bipolar disorder or antidepressant use; losartan or other blood pressure medicines; autoimmune disease; before surgery.
Safety: A losartan interaction is reported; possible side effects are dizziness, headache, insomnia and dry mouth. NCCIH rates it possibly safe for up to 12 weeks only.
Saw Palmetto
Serenoa repens, Berry · Limited evidence
Men use it for urinary flow and nighttime urination linked to mild to moderate BPH; trials measured flow rate, nighttime trips and DHT.
Studied dose: 320 mg standardized berry extract daily|Evidence: 30+ trials; the largest Cochrane review found no clear benefit over placebo
Forms: Berry extract capsules, multi-herb prostate formulas
Who should avoid: Not a substitute for diagnosis: severe or new urinary symptoms, blood in urine or pain need a doctor first.
Safety: Usually well tolerated; mild stomach upset and, in under 5% of users, libido or sexual-function changes are reported in trials.
Slippery Elm
Ulmus rubra, Inner bark · Very limited evidence
Its gel is used to coat a sore throat, mouth or gut; the FDA lists elm bark lozenges, but trials only tested blends.
Studied dose: Lozenge with 10–15 percent elm bark, every 2 hours as needed|Evidence: 45 PubMed records and 0 trials of slippery elm alone
Forms: Lozenges, capsules, powder, tea or warm drink
Who should avoid: Pregnancy and breastfeeding (no safety data); people on oral prescription medicines, especially narrow-dose ones; anyone who has reacted to elm products.
Safety: The gel can slow absorption of other medicines, so take it at least 1 hour after any oral medicine. LiverTox rates it an unlikely cause of liver injury.
St. John's Wort
Hypericum perforatum, Flowers and leaves · Moderate evidence
Used for mild to moderate low mood; trials compared it with SSRIs over 4 to 12 weeks, though 2 large US trials were negative.
Studied dose: 900 mg standardized extract daily, as 300 mg 3 times|Evidence: Meta-analysis of 27 trials matched SSRIs; 2 large US trials found no benefit
Forms: Standardized extract, dried herb capsules
Who should avoid: Anyone on prescription medicines without a pharmacist check, especially the pill, antidepressants, warfarin, digoxin, cyclosporine or HIV drugs; pregnancy, breastfeeding, past manic episode.
Safety: It speeds clearance of many drugs via CYP3A4, lowering levels of the pill, warfarin and cyclosporine; never combine with antidepressants because of serotonin syndrome.
Stinging Nettle
Urtica dioica, Leaf and root (different uses) · Limited evidence
The root is studied for urinary symptoms of an enlarged prostate; the leaf for allergies, joint pain and blood sugar, mostly in small trials.
Studied dose: Root: 459 mg extract daily; leaf: 500 mg extract every 8 hours|Evidence: Only 11 of 41 tagged trials gave nettle alone by mouth; most small
Forms: Leaf capsules, tea, root extract, cooked leaves, fresh leaf on skin
Who should avoid: Pregnancy, trying to conceive or breastfeeding; blood thinners, lithium, diuretics, blood pressure or diabetes medicines; fluid limits for heart or kidney disease.
Safety: Leaf extract lowered blood sugar in a trial, so people on insulin or glucose-lowering drugs, and those on warfarin, lithium or diuretics, should check with a clinician first.
Tongkat Ali
Eurycoma longifolia, Root · Limited evidence
Men use it for testosterone, libido, stress and exercise; small trials measured hormone levels, sexual well-being scores and salivary cortisol.
Studied dose: 200–400 mg standardized root extract daily|Evidence: 15-plus small trials under 120 people; a 9-trial meta-analysis found higher testosterone
Forms: Standardized root extract capsules
Who should avoid: Under 18, pregnancy or breastfeeding, hormone-sensitive conditions such as prostate or breast cancer; ask a doctor if on blood pressure, diabetes or hormone medicines.
Safety: Generally well tolerated at studied doses; restlessness, irritability or trouble sleeping are reported. It may interact with medicines affecting hormones or blood pressure.
Turmeric
Curcuma longa, Root · Moderate evidence
People take it for joint comfort and inflammation; trials of curcumin extracts measured knee osteoarthritis pain and inflammation markers like IL-6.
Studied dose: 500–2000 mg curcumin extract daily, with an absorption enhancer|Evidence: 65-plus trials and meta-analyses; most under 12 weeks with 20–100 people
Forms: Root powder capsules, standardized curcumin extract, piperine or phospholipid forms
Who should avoid: Blood thinners or diabetes drugs; gallstones or bile duct problems; high doses in pregnancy; prior liver disease, chronic alcohol use, women over 50.
Safety: Rare liver injury is reported with concentrated extracts, often with piperine; LiverTox rates it a probable cause (Category C). It may also enhance warfarin's blood-thinning effect.
Yohimbe
Pausinystalia johimbe, Bark · Limited evidence
Used for erectile function, fat loss and workout alertness; the trials cited tested isolated yohimbine, the bark's main alkaloid, not whole bark.
Studied dose: No established safe dose for the bark; trials used isolated yohimbine|Evidence: 7-trial meta-analysis in 419 men tested isolated yohimbine, not whole bark
Forms: Whole-bark capsules, yohimbine HCL (pharmaceutical)
Who should avoid: High blood pressure, anxiety or panic disorder, heart disease or arrhythmia, MAOI antidepressants, kidney or liver disease, pregnancy or breastfeeding.
Safety: Raises blood pressure 5 to 10 mmHg and heart rate, can trigger panic, and carries serious interaction risk with MAOI antidepressants.
No herb matches your search. Try a use (sleep), a plant part (root) or a name (turmeric).
Using herbs safely
Three things worth knowing before you add any herb to your routine.
What the Evidence Ratings Mean
Moderate means several human trials or a meta-analysis agree for one use. Limited means a few small trials. Very limited means mostly lab, animal or traditional data. Few herbs reach Moderate.
Herbs and Medicines
Some herbs change how drugs work. St. John's wort lowers levels of the pill, warfarin and cyclosporine; ginkgo and horse chestnut add to bleeding risk. Tell your pharmacist about every herb you take.
Teas, Tinctures and Capsules
Teas are gentle and hard to dose, tinctures are concentrated alcohol extracts, and capsules give a measured amount. Standardized extracts are closest to what trials used.
Common questions
Are herbal supplements safe?
Natural does not mean risk-free. Herbs can cause side effects and interact with medicines; St. John's wort, for example, lowers blood levels of birth control pills, warfarin and cyclosporine. Tell your doctor or pharmacist about every herb you take, and stop any herb at least 2 weeks before planned surgery.
Are herbal supplements approved by the FDA?
No. In the US, herbs are sold as dietary supplements under a 1994 law. Makers must follow good manufacturing practices, but products do not need FDA approval for safety or effectiveness before sale. Third-party seals such as USP or NSF confirm what is in the bottle.
What is a standardized extract?
It is an extract processed to contain a set amount of a key compound, such as 30% AKBA in boswellia or 16-20% aescin in horse chestnut. Most trial doses refer to standardized extracts, which can differ a lot from the same weight of plain dried herb.
How long do herbs take to work?
Most human trials ran 4 to 12 weeks, and few studied use beyond 6 months. If an herb has not helped after the trial period, more time rarely changes the result, and long-term safety is often unknown.
Can I take herbs while pregnant or breastfeeding?
Most herbs have never been tested in pregnancy, and some, such as damiana, anamu and yohimbe, should be avoided entirely. Do not start any herb while pregnant or breastfeeding without your doctor or midwife.
Should I choose tea, tincture or capsules?
Teas are gentle but hard to dose, tinctures are concentrated alcohol extracts measured in milliliters, and capsules give a fixed amount. If you want to match a study, choose the same standardized extract and dose the trial used.
Why do some herbs have Limited or Very limited evidence?
Because human research on many herbs is small, short or funded by extract makers, and much of it is in cells or animals. We rate the evidence honestly rather than repeat marketing claims, and each guide explains what was actually tested.
Can herbs replace my prescription medicine?
No. Do not stop or swap a prescribed medicine for an herb without your doctor. Several herbs also change how prescription drugs work, which can make treatment less effective or less safe.