Cat's claw is the inner bark of an Amazonian woody vine, used for joint and immune complaints. The 1 name covers 2 different species, which is the first thing most pages get wrong.
Its 2 controlled joint trials are small but real: 45 patients in knee osteoarthritis and 40 in rheumatoid arthritis. Both used specific preparations rather than generic bark.
Quick Answer: What Is Cat's Claw?
Cat's claw is the bark of Uncaria tomentosa or Uncaria guianensis, Amazonian vines named for their hooked thorns. In a 4-week trial of 45 knee osteoarthritis patients, activity pain improved within week 1, and in 40 rheumatoid arthritis patients on standard drugs painful joints fell 53.2% versus 24.1% on placebo.
Key Takeaways
- Cat's claw is the bark of 2 different Amazonian Uncaria species.
- The knee osteoarthritis trial used Uncaria guianensis in 45 patients.
- The rheumatoid trial used 1 purified pentacyclic Uncaria tomentosa extract.
- Painful joints fell 53.2% versus 24.1% on placebo in 24 weeks.
- Immune activity makes it a caution for at least 2 patient groups.
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What Cat's Claw Actually Is
Cat's claw is the inner bark of a woody climbing vine from the Amazon, named for the pair of curved thorns at each leaf node that look like a cat's claws. In Peru it is una de gato, and it has been used traditionally for joint complaints and for what practitioners describe as cleansing.
- Uncaria tomentosa
- The species in most supplements, and the one used in the rheumatoid arthritis trial.
- Uncaria guianensis
- A related species, and the one used in the knee osteoarthritis trial.
- Pentacyclic chemotype
- The alkaloid profile used in the purified RA extract.
- Tetracyclic chemotype
- A different alkaloid profile of the same species, traditionally kept separate.
Those 4 rows are why 2 bottles labelled cat's claw can be genuinely different products. Which form you buy, and what the label should state, is covered in the comparison of tinctures and capsules.
The Osteoarthritis Trial
The clearest human evidence for joint use comes from a 4-week trial in 45 patients with knee osteoarthritis, of whom 30 received freeze-dried Uncaria guianensis and 15 received placebo.[1]Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis — Inflammation Research View source
| Outcome | Result | Reading |
|---|---|---|
| Pain associated with activity | Significantly reduced | Benefits within the first week |
| Medical and patient assessments | Significantly improved | Both scores moved |
| Knee pain at rest | Not significantly reduced | A real limitation |
| Knee pain at night | Not significantly reduced | Also unchanged |
| Blood and liver function | No deleterious effects | Versus placebo, over 4 weeks |
Rows 3 and 4 rarely appear in marketing, and they matter. Pain while moving improved; pain lying in bed did not, in that 4-week window.
The Rheumatoid Arthritis Trial
The second controlled study is different in almost every respect: a different species, a purified extract, a different disease and a much longer run. Forty patients already taking sulfasalazine or hydroxychloroquine were randomized for 24 double-blind weeks.[2]Randomized double blind trial of an extract from the pentacyclic alkaloid-chemotype of Uncaria tomentosa for the treatment of rheumatoid arthritis — Journal of Rheumatology View source
- Painful joints: Down 53.2% versus 24.1% on placebo.
- Design: Add-on to existing disease-modifying drugs, never a replacement.
- Second phase: 28 further weeks with everyone on the extract.
- Authors' word: Modest, from a small preliminary study.
Anyone with rheumatoid arthritis should read that design twice. The detail sits in the arthritis evidence page.
What About Immunity?
Cat's claw has an immune reputation built on laboratory work and 1 small human study of a water-soluble extract and pneumococcal vaccine response.[3]Persistent response to pneumococcal vaccine in individuals supplemented with a novel water soluble extract of Uncaria tomentosa, C-Med-100 — Phytomedicine View source
- What exists: Small trials of specific proprietary extracts.
- What does not: Any large trial of fewer infections.
- The catch: Immune activity is a caution in autoimmune disease.
- Parasites: A popular claim with no human trial behind it.
That last line answers a question people genuinely search for. Traditional use is not the same as tested, and an antiparasitic claim needs more than folklore.
Cancer: What the Study Actually Said
Cat's claw and cancer is a common search, and the honest answer comes from a phase II study in 51 patients with advanced solid tumours who had no remaining treatment options.[4]Uncaria tomentosa (cat's claw) improves quality of life in patients with advanced solid tumors — Journal of Alternative and Complementary Medicine View source
| What was measured | Result |
|---|---|
| Overall quality of life | Improved, p = 0.0411 |
| Fatigue | Reduced, p = 0.0496 |
| Inflammatory markers such as CRP and TNF-alpha | No significant change |
| Tumour response by RECIST criteria | None detected |
Row 4 is the whole story. The study reported better quality of life and explicitly no tumour response, and anyone in cancer care should raise any supplement with their oncology team.
How Much People Take
Traditional and commercial doses differ, and the trials used specific preparations rather than generic bark. That makes a single universal number impossible, though the practical ranges are consistent.
| Form | Typical daily amount | Note |
|---|---|---|
| Bark capsules | 1000 to 3000 mg | 1 to 3 capsules of 1000 mg |
| Tincture | 1 to 3 mL, usually split | Follow the bottle, dilute in water |
| Purified extract, RA trial | A specific pentacyclic extract | Not equivalent to bark |
| Bark decoction | Simmered, traditional | Woody bark needs simmering |
Our own bottle sits in row 1 at 1000 mg of bark per capsule, which keeps the daily count simple. The full breakdown is in the dosage guide.
Who Should Not Take It
Cat's claw is immune-active, and that single property sets most of its cautions. They are specific rather than decorative.
- Transplant recipients: Do not take it; immunosuppression is deliberate.
- Autoimmune disease: A clinician conversation before starting.
- Pregnancy: Avoid, including traditional contraceptive use in its history.
- Before surgery: Mention it, and expect to stop 2 weeks ahead.
The complete list, including the medication classes worth checking, is in who should not take it and why.
Frequently Asked Questions
What does cat's claw do for you? +
Its tested use is joint comfort. In 45 knee osteoarthritis patients, activity-related pain improved within the first week over a 4-week trial, and in 40 rheumatoid arthritis patients on standard drugs painful joints fell 53.2% versus 24.1% on placebo.
Is cat's claw the same as Uncaria tomentosa? +
Usually, but not always. Two species are sold as cat's claw: Uncaria tomentosa, used in the rheumatoid arthritis trial, and Uncaria guianensis, used in the knee osteoarthritis trial. A label should name which of the 2 it contains.
Who should not take cat's claw? +
Transplant recipients, anyone on immunosuppressant or biologic therapy, people with autoimmune disease without clinician input, anyone pregnant or breastfeeding, and anyone within 2 weeks of surgery. That is 5 groups in total.
Can you take cat's claw every day? +
The rheumatoid arthritis trial ran 24 double-blind weeks plus 28 more, with only minor side effects reported, so daily use over months has been studied. Anyone with an autoimmune condition should still get clinician agreement first.
Does cat's claw help arthritis? +
In 2 small controlled trials, yes, modestly. Knee osteoarthritis patients improved on activity pain within 1 week, though rest and night pain did not change, and rheumatoid arthritis patients saw painful joints fall 53.2% as an add-on to their drugs.
Is cat's claw hard on the kidneys? +
The osteoarthritis trial monitored blood and liver function across 4 weeks and found no deleterious effects versus placebo. Kidney-specific data are limited, so anyone with kidney disease should treat it as a clinician question.
Does cat's claw get rid of parasites? +
Not 1 human trial supports that. It is a traditional claim that circulates widely, while the 2 tested uses are joint comfort and immune markers. Suspected parasites need testing and treatment rather than a bark capsule.
Can cat's claw treat cancer? +
No. A phase II study in 51 patients with advanced tumours found better quality of life and less fatigue, and stated that no tumour response was detected. Anyone in treatment should raise supplements with their oncology team.
What not to mix with cat's claw? +
Immunosuppressants such as cyclosporine and tacrolimus are the clearest concern, followed by blood pressure medication, anticoagulants and drugs processed by the CYP3A4 enzyme. A pharmacist can check a full list in 2 minutes.
How long does cat's claw take to work? +
Faster than most joint herbs in 1 respect: the osteoarthritis trial saw activity pain improve within the first week. The rheumatoid arthritis benefit was measured at 24 weeks, so allow at least 4 to 8 weeks for a fair personal trial.
Is tincture better than capsules? +
Neither is stronger by default; they differ in how you dose and absorb them. A 2 fl oz tincture suits people who want flexible drops, while 1000 mg capsules make the daily amount countable without measuring.
Is cat's claw safe for the liver? +
In the 4-week osteoarthritis trial, liver function showed no deleterious changes compared with placebo. That covers 45 patients over 1 month rather than years, so existing liver disease remains a reason to ask first.
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