What L-Leucine Is
Leucine is 1 of the 9 essential amino acids, which means your body cannot make it and food has to supply it. It is also 1 of the 3 branched-chain amino acids, with isoleucine and valine. Remedy's L-Leucine holds 1000 mg of L-leucine per vegan capsule, with 60 capsules per bottle.
Leucine is best known as the amino acid that tells muscle a protein meal has arrived. That signal is real. Whether it builds muscle over months is a separate question, and this page answers both.
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1000 mg per capsule: 1 g of L-leucine, the only active ingredient.
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60 capsules: 2 months at the label dose of 1 a day.
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Essential amino acid: Supplied by protein foods every day.
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Not for: Anyone with maple syrup urine disease.
The full evidence map is in what L-leucine is and what the trials show.
Supplement Facts
Serving size: 1 Vegan Capsule. Servings per container: 60.
| Amount Per Serving |
Amount |
% Daily Value |
| L-Leucine |
1000 mg |
† |
† Daily Value not established.
Other ingredients: Cellulose, glycerin, water (vegan capsule).
Directions: One capsule daily.
Made in the USA.
What Leucine Does in Hours
When enough leucine reaches muscle after a meal, it switches on mTORC1, the pathway that starts building new muscle protein. In older men, adding 2.5 g of leucine to 20 g of casein raised muscle protein synthesis by 22% over 6 hours.[1]Leucine co-ingestion and muscle protein accretion in elderly men — Clinical Nutrition (2013) View source
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The signal: Leucine activates mTORC1 within hours of eating.
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Older muscle: Responds less to protein, and more to extra leucine.
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The limit: Building protein still needs all 9 essential amino acids.
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The measurement: Taken over hours in a lab, not over months.
That last point is the one most leucine pages skip, and it is why the next section matters more than this one.
What the Long-Term Trials Show
A faster synthesis rate for a few hours is a mechanism. Muscle gained over weeks is a result. These counts came off PubMed on 2026-10-08, and anyone can rerun them.
| What PubMed holds on leucine |
Count |
| Records on eating or supplementing leucine |
1,156 |
| Of those, tagged as clinical trials |
191 |
| Leucine alone vs control, 8+ weeks, muscle or strength measured |
13 |
| Of those 13, more muscle or strength than control |
4 |
| Systematic reviews or meta-analyses |
14 |
A 2015 meta-analysis of 9 trials in older people found synthesis rose while lean body mass did not differ from control.[2]Leucine, muscle protein synthesis and lean mass in older people: meta-analysis — British Journal of Nutrition (2015) View source In trained men eating plenty of protein, 10 g of leucine a day for 12 weeks added nothing over placebo.[3]Leucine has no further effect on training-induced muscle adaptations — Medicine and Science in Sports and Exercise (2020) View source
We make no muscle-building claim for this product, because the long trials do not support one. Every trial, sorted by result, is in does leucine build muscle.
One Capsule Against the Meal Threshold
The studies that showed the leucine signal used about 2.5 to 3 g of leucine in a meal. It takes about 25 g of whey protein to supply 2.7 g.[4]Protein content and amino acid composition of protein isolates — Amino Acids (2018) View source One capsule is 1 g, so here is the arithmetic.
| Goal |
Capsules |
Days per bottle |
| Top up 1 meal by 1 g (label dose) |
1 a day |
60 |
| Supply the whole 2.5 to 3 g at 1 meal |
3 a day |
20 |
| Match the 7.5 g a day of the long trials |
7 to 8 a day |
About 8 |
| Supply 3 g at each of 3 meals |
9 a day |
About 6.7 |
The honest use is the first row: a 1 g top-up for a meal that is already close. Food by food, the threshold is worked out in leucine-rich foods and the meal threshold.
Food First, Capsule Second
Most people get their leucine from protein foods, and most mixed meals with a decent protein serving come close to the mark without help.
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Whey: About 25 g of protein for 2.7 g of leucine.
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Milk protein: About 31 g for the same amount.
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Egg protein: About 39 g.
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Soy protein: About 40 g.
Breakfasts and plant-based meals are the usual shortfalls. That is where a single capsule can make up a 1 g gap.
For Older Adults
Older muscle needs more protein per meal to respond, about 0.40 g per kg against 0.24 g in young men, and older adults may need about 78.5 mg of leucine per kg a day.[5]Dietary leucine requirement of older men and women — American Journal of Clinical Nutrition (2021) View source That is why leucine is often bought for parents.
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Short studies: Extra leucine lifted the response of older muscle.
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Long trials: 7.5 g a day for 3 to 6 months did not add muscle in older men.
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What helps more: Resistance training and enough protein at each meal.
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Where a capsule fits: A top-up for small, low-protein meals.
The older-adult evidence is set out in leucine for older adults and sarcopenia.
Leucine, BCAAs, Whey and HMB
These 4 are sold for the same goal but supply very different things. Building new muscle protein needs all 9 essential amino acids.
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L-leucine: 1 essential amino acid, 1 g per capsule.
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BCAAs, 2:1:1: 3 essential amino acids, half of the weight leucine.
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Whey protein: All 9, with about 2.7 g of leucine per 25 g of protein.
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HMB: A leucine metabolite; only about 5% of leucine becomes HMB.
The comparison, with cost per gram, is in leucine vs BCAA vs whey vs HMB.
How to Take It
The label dose is 1 capsule daily, taken with the meal that is lowest in protein. The leucine studies gave it with food, and timing matters less than total daily protein.
| Question |
Answer |
| How many |
1 capsule daily, as on the label |
| When |
With the meal lowest in protein |
| With food |
Yes, as in the studies |
| How long |
Review after 3 months; the longest trial ran 6 months |
Adults need about 39 mg of leucine per kg a day from all food, roughly 2.7 g at 70 kg. Requirements, trial doses and limits are in how much leucine per day.
Safety and Who Should Avoid It
At modest doses leucine is well tolerated. The cautious upper limit in short studies was about 500 mg per kg a day, roughly 35 g at 70 kg, where blood ammonia began to rise.[6]Tolerable upper intake level of leucine in young men — American Journal of Clinical Nutrition (2012) View source A capsule is 1 g.
| Situation |
Position |
| Maple syrup urine disease |
Do not take it |
| Insulin or other glucose-lowering medicine |
Ask your prescriber first |
| Kidney or liver disease, or a protein-restricted diet |
Ask your clinician first |
| Pregnant or breastfeeding |
No trials; ask your clinician |
| Children and teenagers |
Not for children without a doctor |
Maple syrup urine disease affects about 1 in 185,000 infants worldwide.[7]Maple syrup urine disease — MedlinePlus Genetics, National Library of Medicine View source Taken with glucose, leucine raised the insulin response by 66%, so diabetes medicines need care.[8]Leucine with glucose, insulin secretion and blood glucose — Metabolism (2008) View source The full list is in leucine side effects and safety.
Why Choose Remedy's L-Leucine
No trial makes 1 leucine capsule better than another, so the honest differentiators are what is in the bottle and what this page is willing to say.
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Single ingredient: 1000 mg of L-leucine, nothing else active.
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Countable: 1 capsule is exactly 1 g, so the meal arithmetic is easy.
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Vegan capsule: Cellulose-based, per the label.
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No muscle promise: Because 9 of 13 long trials found no added muscle.
What we will not say matters as much as what we will, and on this page that means no claim to build muscle or treat any condition.
Frequently Asked Questions
What is L-leucine? +
L-leucine is the natural form of leucine, 1 of the 9 essential amino acids found in protein. Each capsule holds 1000 mg, which is 1 g of L-leucine, and the bottle holds 60 capsules.
Does L-leucine build muscle? +
It switches on muscle protein synthesis for a few hours after a meal. Over months the record is weaker: of 13 trials giving leucine alone for 8 weeks or more, 9 found no added muscle or strength, so we make no muscle claim.
How many capsules equal the leucine in a protein shake? +
About 25 g of whey protein supplies 2.7 g of leucine, so roughly 3 capsules match it on leucine. The shake also supplies all 9 essential amino acids, which the capsules do not.
How long does 1 bottle last? +
60 days at the label dose of 1 capsule daily. At 3 capsules a day it lasts 20 days, and at the 7.5 g a day used in long trials about 8 days.
Can I take it with a protein shake or a meal? +
Yes. The studies gave leucine with protein or a meal, and 1 capsule adds 1 g of leucine to whatever that meal already supplies.
Is it vegan? +
Yes. The label lists a vegan capsule made from cellulose, with glycerin and water as the other ingredients, and 1000 mg of L-leucine per capsule.
Who should not take L-leucine capsules? +
Anyone with maple syrup urine disease, about 1 in 185,000 infants. Ask a clinician first if you take insulin or other glucose-lowering medicine, have kidney or liver disease, or are pregnant.
Can older adults take it? +
Yes, with their clinician's agreement if they take medicines. Short studies show extra leucine helps older muscle respond to a meal, while 7.5 g a day for 3 to 6 months did not add muscle on its own.
Is L-leucine the same as BCAA? +
No. BCAAs are 3 amino acids, usually 2:1:1, so half the weight is leucine. 1 capsule of L-leucine gives 1 g of leucine; our 2-capsule BCAA serving gives 500 mg.
Can I take more than 1 capsule a day? +
Trials used 2 to 10 g a day without safety problems, and the cautious upper limit is about 35 g at 70 kg. More capsules has not shown more muscle, so 1 a day suits the top-up use.
Does leucine affect blood sugar? +
Taken with glucose it raised insulin release by 66% in 13 adults, but 7.5 g a day for 6 months did not change HbA1c in men with type 2 diabetes. Ask first if you use diabetes medicine.
Should I take it in the morning or at night? +
0 trials compared timing. Take it with the meal that is lowest in protein, often breakfast, at a time you will remember.
You May Also Like
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HMB 1000 mg — the leucine metabolite, at the 1 g unit trials build their 3 g dose from
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Chocolate Whey Protein — the complete protein that supplies leucine with all 9 essential amino acids
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BCAA 1000 mg 2:1:1 — leucine with isoleucine and valine, 500 mg of leucine per serving
