Performance
Leucine
Also known as: L-Leucine, BCAA component
Primary amino acid triggering muscle protein synthesis. Can boost lower-protein meals.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every Leucine product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Thorne Creatine + BCAAs | 92 A | $1.73 |
| 2 | NutraBio L-Leucine | 90 A | $0.49 |
| 3 | NutraBio BCAA 2500 | 90 A | $0.56 |
| 4 | Kaged BCAA 2:1:1 | 89 A | $0.42 |
| 5 | Thorne SynaQuell +™ | 88 A | $1.47 |
| 6 | Thorne Amino Complex - Travel Packs - Berry | 85 A- | $1.20 |
| 7 | Thorne Amino Complex - Travel Packs - Lemon | 85 A- | $1.20 |
| 8 | Thorne Amino Complex - Berry | 84 A- | $1.47 |
| 9 | Thorne Amino Complex - Lemon | 84 A- | $1.47 |
| 10 | Sports Research Whey Protein, Dutch Chocolate | 83 A- | $2.21 |
| 11 | Life Extension Branched Chain Amino Acids (Free Form) | 82 A- | $0.68 |
| 12 | Sports Research Keto+, Raspberry Lemonade | 82 A- | $1.60 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much Leucine should I take?
The typical range is 2.5-5g to boost a meal. As needed
When should I take Leucine?
With lower-protein meals. With protein-containing meals.
Which form of Leucine is best?
Powder — Bitter taste. Other forms in the catalog: Capsule.
Is Leucine safe?
Commonly reported: Bitter taste, GI upset. Serious warnings: None. Normal amino acid considerations
Which Leucine supplement scores highest?
Thorne Creatine + BCAAs, at 92/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Primary uses
- Muscle protein synthesis trigger
- Protein quality enhancement
What systematic reviews concluded
Outcomes that systematic reviews of Leucine reached a verdict on: 2 with a benefit, 2 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (2)
“Specific AAs (i.e., leucine and isoleucine) co-ingested with glucose exerted a synergistic effect on the postprandial insulin response and attenuated the glucose response compared to glucose intake alone in healthy participants.” PMID 33096658
“Oral AA ingestion as well as intravenous AA infusion was able to stimulate an insulin response and decrease glucose concentrations in T2DM and obese individuals.” PMID 33096658
Not enough to say: pressure ulcer prevention/healing; glucose homeostasis in glucose-intolerant rodents.
How it works
- Primary mTOR activator
- Threshold amount triggers MPS (~2.5-3g)
- Most anabolic amino acid
Dosage
- Typical range
- 2.5-5g to boost a meal
- Timing
- With lower-protein meals
- With food
- With protein-containing meals
- Duration
- As needed
- Special populations
- Elderly, low-protein meals, plant-based eaters
Forms
- Powder
- Capsule
Safety
Common side effects
- Bitter taste
- GI upset
Contraindications
- MSUD
Products containing Leucine
Top-scoring supplements in our catalog that list Leucine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Known interactions
Evidence notes
Well-established as MPS trigger
Grade A: Multiple well-designed human trials support the main claims.
Related in Performance
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.