Adults need roughly 34 to 39 mg of leucine per kg a day, which ordinary protein covers, while trials added 2 to 10 g. A requirement and a supplement dose answer 2 different questions.
This page keeps them apart, then converts each into capsules.
Quick Answer: How Much Leucine Per Day?
The requirement is about 39 mg per kg a day, roughly 2.7 g for a 70 kg adult, and may be double that after 60. Supplement studies added 2.5 to 3 g per meal, or 2 to 10 g a day. The cautious upper limit is 500 mg per kg, about 35 g.
Key Takeaways
- International guidance sets leucine at 39 mg per kg a day.
- A 2024 study put young men's requirement near 34 mg per kg.
- Long trials gave 7.5 g daily, split as 2.5 g per meal.
- Blood ammonia rose above about 500 mg per kg a day.
- Our bottle holds 60 g, or 8 days at trial doses.
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Requirement Versus Supplement Dose
Two different numbers get mixed up. The requirement is the minimum your body needs each day from all food. A supplement dose is extra leucine on top, usually to push 1 meal higher. Both sit inside what the leucine research adds up to.
| Measure | Per kg a day | For a 70 kg adult |
|---|---|---|
| International guidance | 39 mg | About 2.7 g |
| Young men, 2024 estimate | 34 mg | About 2.4 g |
| Adults over 60, 2021 estimate | 78.5 mg | About 5.5 g |
| Cautious upper limit, young men | 500 mg | About 35 g |
| Cautious upper limit, older men | 351 mg | About 24.5 g |
The older-adult estimate came from 16 people over 60.[1]Dietary leucine requirement of older men and women is higher than current recommendations — American Journal of Clinical Nutrition (2021) View source The young-adult figure came from 10 men.[2]Leucine requirement determined in healthy young adult males using the indicator amino acid oxidation method — American Journal of Clinical Nutrition (2024) View source
Doses Used in the Studies
Short studies added 2.5 to 5 g to a single meal, on top of what the 2.5 to 3 g meal arithmetic says food supplies. Long trials gave 2 to 10 g a day for 8 weeks to 6 months, and none found a reliable muscle dose.
- Single meal: 2.5 g added to 20 g of casein in older men.
- Per meal for 3 days: 5 g with each meal, 15 g a day.
- Long trials: 7.5 g a day, as 2.5 g with each main meal.
- Highest long-trial dose: 10 g a day for 12 weeks.
Capsule Counts at Each Dose
Our capsule holds 1000 mg, so the conversion is simple: 1 capsule is 1 g. The bottle holds 60 capsules, 60 g in all, at $17.99, about 30 cents a gram.
| Goal | Capsules a day | Days per 60-capsule bottle |
|---|---|---|
| Top up 1 meal (our label dose) | 1 | 60 |
| 1 g with each of 3 meals | 3 | 20 |
| 2.5 g with each of 3 meals, as in the long trials | 7 to 8 | About 8 |
| The full 3 g at each of 3 meals | 9 | About 6.7 |
Our label directions are 1 capsule daily, which is the top-up use. At that dose the 1000 mg capsules we sell last 2 months.
Timing: With Meals, Not Instead of Them
Every positive short study gave leucine with protein or a meal. Timing around training matters less than total daily protein, so take it with the meal that is shortest on protein.
- With a meal: How the studies gave it.
- Around training: A convenience, not a requirement.
- Before bed: No leucine trial tested it.
- On an empty stomach: Not tested for muscle.
A meta-regression of 49 training trials found protein's effect on fat-free mass levelled off near 1.62 g per kg a day.[3]A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength — British Journal of Sports Medicine (2018) View source
How Far a Capsule Sits Below the Limit
The upper limit was set in short metabolic studies. In young men, blood ammonia rose above normal beyond 500 mg per kg a day, so that figure, about 35 g, became the cautious limit.
The young-men limit came from 5 volunteers.[4]Determination of the tolerable upper intake level of leucine in acute dietary studies in young men — American Journal of Clinical Nutrition (2012) View source The older-men figures came from a 2016 review.[5]Safety and Tolerability of Leucine Supplementation in Elderly Men — Journal of Nutrition (2016) View source
- Young men: About 500 mg per kg, 35 g at 70 kg.
- Older men: The same 500 mg, or 351 mg per kg as a cautious figure.
- In capsules: 24 capsules is still under the cautious older-adult limit.
- The caveat: These were studies of days, not years.
What happens nearer those levels is in the upper limit and side effects.
Speak to a Clinician Before Taking Leucine If
- You have maple syrup urine disease or any other disorder of leucine metabolism
- You take insulin or another medicine that lowers blood sugar
- You have kidney or liver disease, or follow a protein-restricted diet
- You are pregnant or breastfeeding, where no leucine supplement trials exist
- You are buying it for a child or a teenager
Frequently Asked Questions
How much leucine should you take for muscle growth? +
No dose has reliably added muscle in people eating enough protein. Short studies used 2.5 to 3 g per meal; long trials used 2 to 10 g a day.
When is the best time to take leucine? +
With a meal, ideally the one lowest in protein. 0 trials compared morning with evening, and timing matters less than total protein.
Is 10g of leucine too much? +
Not for safety: 10 g is well under the cautious limit of about 35 g a day. It is more than needed, though; 10 g a day added nothing in trained men over 12 weeks.
Can I take L-leucine and creatine together? +
We found 0 trials showing a problem with combining them. They work by different routes. Start 1 at a time if you want to judge either.
Can I take leucine on an empty stomach? +
It has not been tested for muscle that way. The studies gave 2.5 to 5 g with protein or a meal, so with food is the evidence-based choice.
Should I take leucine before bed? +
No leucine trial tested bedtime dosing. If dinner is your lowest-protein meal, take it with dinner; 1 capsule adds 1 g.
How long does a bottle of leucine last? +
60 days at the label dose of 1 capsule. At the 7.5 g a day used in long trials it would last 8 days.
Do women need less leucine? +
Needs scale with body weight. At 39 mg per kg, a 60 kg woman needs about 2.3 g a day; the 2021 older-adult study found no difference by sex.
Should I cycle leucine? +
No study tested cycling. The longest trial ran 6 months at 7.5 g a day; reviewing after 3 months is a sensible checkpoint.
Related Reading
- What 13 Long-Term Leucine Trials Showed
- Daily Leucine Needs After 60
- Leucine or a BCAA Blend?
- Leucine Before a Workout: Timing Notes
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