L-Lysine
Also known as: lysine, L-lysine monohydrochloride
Randomized trials in humans have reported reduced diarrhoeal episodes in children and reduced respiratory morbidity in adult men with 1 g/day lysine in a peri‑urban Ghanaian population. A short-term 5 g/day supplementation did not increase the lysine catabolite alpha-aminoadipic acid (2-AAA) in healthy adults. Systematic reviews of clinical trials indicate doses up to ~17 g/day have been used and identify a provisional no-observed-adverse-effect level of about 6 g/day based on gastrointestinal symptoms.
Last reviewed: 2026-10-14 · 5 indexed studies
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Overview
L-lysine is an essential amino acid commonly consumed in food and available as an oral supplement. Human trials report modest clinical effects for specific outcomes (for example reduced diarrhoeal morbidity in one community trial) and an extensive safety literature showing mainly gastrointestinal adverse events at high doses.
Mechanism & Function
Mechanism of Action
Lysine is incorporated into proteins and is a precursor for several metabolic pathways; it can modulate mucosal repair and intestinal transport and may influence immune or neurochemical pathways implicated in infection and anxiety. In hereditary ornithine aminotransferase deficiency (gyrate atrophy) lysine can reduce plasma ornithine via metabolic pathway interactions.
Physiological Role
Essential amino acid required for protein synthesis, nitrogen balance and multiple metabolic pathways including lysine catabolism to 2-AAA and interactions with the ornithine pathway.
Primary Pathways
Performance / Health Relevance
No convincing evidence for effects on exercise glucose tolerance or training adaptations from available randomized trials; primary human evidence supports modest effects on infectious morbidity in specific populations rather than athletic performance.
Evidence Review
Practical Use & Dosage
- Minimum Effective Dose
- 1 g/day (reduced diarrhoeal episodes in one RCT)
- Optimal Range
- Not established for general use; trials have used 1 g/day to >16 g/day for safety assessment
- Upper / Caution Level
- Provisional no-observed-adverse-effect level ~6 g/day (systematic review); doses up to ~17 g/day have been studied with mainly gastrointestinal adverse events
- Timing
- Not established
- Best Format
- Oral free amino acid (powder or tablet)
- Bioavailability
- Well absorbed orally as a free amino acid; specific formulations not shown to alter clinical outcomes in available trials
- Absorption Considerations
- High single doses may increase risk of gastrointestinal symptoms
Safety & Interactions
Side Effects
- •Gastrointestinal symptoms (nausea, diarrhoea, abdominal discomfort) reported at higher doses
- •Occasional subjective adverse events reported in trials
Contraindications
- Specific metabolic disorders should be managed under specialist care (for example gyrate atrophy — treatment decisions guided by specialists)
Drug Interactions
- •No specific drug interactions robustly documented in the provided human trial abstracts
Who Should Avoid
- •People with inborn errors of amino acid metabolism should follow specialist advice
- •Individuals with persistent gastrointestinal sensitivity at higher amino acid doses
Monitoring
Monitor for gastrointestinal adverse events at higher doses; in rare metabolic disorders, monitor plasma ornithine and specialist‑recommended biomarkers.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is L-Lysine typically used or indicated?
L-Lysine is most commonly used for: General amino acid supplementation, Support for protein nutrition, Occasional use for reducing infectious/diarrhoeal morbidity in low‑income settings, Adjunct in rare metabolic disorder management (gyrate atrophy). Essential amino acid required for protein synthesis, nitrogen balance and multiple metabolic pathways including lysine catabolism to 2-AAA and interactions with the ornithine pathway.
How does L-Lysine work?
Lysine is incorporated into proteins and is a precursor for several metabolic pathways; it can modulate mucosal repair and intestinal transport and may influence immune or neurochemical pathways implicated in infection and anxiety. In hereditary ornithine aminotransferase deficiency (gyrate atrophy) lysine can reduce plasma ornithine via metabolic pathway interactions.
What is the recommended dose of L-Lysine?
The optimal range is Not established for general use; trials have used 1 g/day to >16 g/day for safety assessment. with a minimum effective dose of 1 g/day (reduced diarrhoeal episodes in one RCT). Best taken: Not established. Upper / caution level: Provisional no-observed-adverse-effect level ~6 g/day (systematic review); doses up to ~17 g/day have been studied with mainly gastrointestinal adverse events.
What are the side effects of L-Lysine?
Reported side effects include: Gastrointestinal symptoms (nausea, diarrhoea, abdominal discomfort) reported at higher doses; and Occasional subjective adverse events reported in trials. Monitoring: Monitor for gastrointestinal adverse events at higher doses; in rare metabolic disorders, monitor plasma ornithine and specialist‑recommended biomarkers.
Does L-Lysine interact with medications?
Known or theoretical interactions: No specific drug interactions robustly documented in the provided human trial abstracts. Always check with a clinician before combining with prescription medication.
Who should avoid L-Lysine?
L-Lysine is generally not recommended for: People with inborn errors of amino acid metabolism should follow specialist advice; Individuals with persistent gastrointestinal sensitivity at higher amino acid doses; and Specific metabolic disorders should be managed under specialist care (for example gyrate atrophy — treatment decisions guided by specialists).
How strong is the evidence for L-Lysine?
Evidence level: Moderate (overall score 62/100), based on 5 indexed studies on SuppIndex.
Research & References (5)
The consumption of animal products is associated with plasma levels of alpha-aminoadipic acid (2-AAA).
Randomized cross-over dietary intervention including a lysine supplementation arm (5 g/day for 1 week) in healthy individuals, plus short-term vegetarian diet intervention.
Effect of lysine supplementation on health and morbidity in subjects belonging to poor peri-urban households in Accra, Ghana.
Double-blind randomized trial of 1 g/day lysine versus placebo in peri-urban Ghanaian adults and children assessing morbidity, growth and biomarkers.
Effects of arginine/lysine supplementation and resistance training on glucose tolerance.
Randomized study of combined arginine/lysine supplementation (dose based on fat-free mass; combined product) with and without resistance training in young men, assessing glucose tolerance.
Comprehensive Safety Assessment of l-Lysine Supplementation from Clinical Studies: A Systematic Review.
Systematic review of clinical studies of oral l-lysine supplementation (71 articles, 3357 subjects) focusing on safety across doses from ~16.8 to 17.5 g/day and durations up to 1095 days.
A review of treatment modalities in gyrate atrophy of the choroid and retina (GACR).
Systematic review of treatments for gyrate atrophy identified l-lysine supplementation among reported interventions; evidence primarily from case reports and small series.
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Beta-Alanine
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EAA Blend
78/100Free-form blend of 9 EAAs (Leu, Ile, Val, Lys, Met, Phe, Thr, Trp, His) at evidence-based ratios; bypasses gastric digestion for rapid plasma aminoacidaemia.
Research Overview
Moderate EvidenceCite this ingredient
One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.
Stable URL
https://thesuppindex.com/ingredients/l-lysine
SuppIndex. (2026). L-Lysine: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/l-lysine
Based on 5 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Commonly combined with other amino acids in supplements; evidence for additive clinical benefit when combined (for example arginine+lysine) is not robust in the provided abstracts.