Amino Acid
L-Isoleucine
Also known as: Isoleucine, Ile, BCAA
Essential branched-chain amino acid (BCAA) important for muscle protein synthesis, energy production during exercise, and immune function.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every L-Isoleucine product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Thorne Creatine + BCAAs | 92 A | $1.73 |
| 2 | Nutricost L-Isoleucine Capsules | 92 A | $0.30 |
| 3 | BulkSupplements L-Isoleucine Powder | 91 A | $0.05 |
| 4 | NutraBio BCAA 2500 | 90 A | $0.56 |
| 5 | Kaged BCAA 2:1:1 | 89 A | $0.42 |
| 6 | Thorne SynaQuell +™ | 88 A | $1.47 |
| 7 | Thorne Amino Complex - Travel Packs - Berry | 85 A- | $1.20 |
| 8 | Thorne Amino Complex - Travel Packs - Lemon | 85 A- | $1.20 |
| 9 | Thorne Amino Complex - Berry | 84 A- | $1.47 |
| 10 | Thorne Amino Complex - Lemon | 84 A- | $1.47 |
| 11 | Life Extension Branched Chain Amino Acids (Free Form) | 82 A- | $0.68 |
| 12 | Pure Encapsulations Essential Aminos | 81 A- | $0.31 |
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 L-Isoleucine should I take?
The typical range is 3-6 g daily. Safe long-term
When should I take L-Isoleucine?
Pre/during/post workout. With or without.
Which form of L-Isoleucine is best?
Powder — Often in BCAA blends. Other forms in the catalog: Capsule.
Is L-Isoleucine safe?
Commonly reported: Well tolerated. Serious warnings: Maple syrup urine disease contraindicated. Caution in liver disease
Which L-Isoleucine 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 recovery
- Exercise performance
- Blood sugar regulation
- Hemoglobin synthesis
What systematic reviews concluded
Outcomes that systematic reviews of L-Isoleucine reached a verdict on: 2 with a benefit. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (2)
“attenuated the glucose response compared to glucose intake alone in healthy participants” PMID 33096658
“exerted a synergistic effect on the postprandial insulin response and attenuated the glucose response compared to glucose intake alone in healthy participants” PMID 33096658
How it works
- Activates mTOR pathway for muscle protein synthesis
- Oxidized in muscle for energy during exercise
- Precursor for glucose during fasting
- Supports hemoglobin production
Dosage
- Typical range
- 3-6 g daily
- Timing
- Pre/during/post workout
- With food
- With or without
- Duration
- Safe long-term
- Special populations
- Athletes, those in caloric deficit
Forms
- Powder
- Capsule
Safety
Common side effects
- Well tolerated
Contraindications
- MSUD
- ALS (controversial)
Products containing L-Isoleucine
Top-scoring supplements in our catalog that list L-Isoleucine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Evidence notes
Well-studied as part of BCAAs for exercise performance
Grade B: Some human trials support key claims; further confirmation needed.
Related in Amino Acid
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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.