What is the recommended dosage for L-Ornithine?

Sleep: 400-800 mg, 30-60 min before bed

What are the side effects of L-Ornithine?

Potential side effects include: GI discomfort at high doses (diarrhea), Insomnia at very high doses (paradoxical in some individuals).

What is L-ornithine and how might it affect sleep?

L-ornithine is a non-essential amino acid involved in the urea cycle, which detoxifies ammonia in the body. Elevated ammonia levels can cause fatigue and disrupt sleep. Two Japanese clinical trials found that L-ornithine supplementation (400-800 mg before bed) reduced morning cortisol levels and improved self-reported sleep quality and feelings of refreshment upon waking. The evidence is promising but limited in scale. Consult your healthcare provider.

How does L-ornithine help with sleep quality?

L-ornithine is a non-proteinogenic amino acid that plays a central role in the urea cycle, helping the body detoxify ammonia. Elevated blood ammonia levels are associated with fatigue and poor sleep quality, particularly after physical exertion or alcohol consumption. A randomized controlled trial with 52 healthy adults found that 400 mg of L-ornithine taken before bed improved subjective sleep quality and reduced morning fatigue, potentially by enhancing ammonia clearance during sleep. Research suggests L-ornithine may also reduce cortisol levels, which could support sleep in individuals with stress-related sleep difficulties.

Is L-ornithine more helpful for sleep after exercise or alcohol?

L-ornithine may be particularly relevant for sleep quality after situations that increase ammonia load — specifically intense exercise and alcohol consumption. A study of Japanese office workers found L-ornithine supplementation (400 mg/day) improved next-day alertness and reduced feelings of fatigue, especially in those with mild stress. Another study showed L-ornithine combined with L-arginine reduced exercise-induced ammonia levels and improved recovery sleep. While the overall evidence base is preliminary, L-ornithine may support sleep quality in specific contexts where ammonia accumulation disrupts rest.

L-Ornithine

amino-acid

Also known as: L-Ornithine HCl, Ornithine

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About

L-Ornithine is a non-proteinogenic amino acid involved in the urea cycle. Research suggests it may support sleep quality by reducing cortisol and ammonia levels, particularly in individuals under stress or after alcohol consumption. A Japanese RCT found L-ornithine improved subjective sleep quality and reduced next-morning fatigue.

How It Works

Facilitates ammonia detoxification via the urea cycle; reduces cortisol through HPA axis modulation; may reduce stress-induced hyperarousal that impairs sleep.

Evidence For Conditions

Condition	Grade	Studies	Participants
Shift Work Sleep Disorder	C	3	--	View →
Insomnia	C	2	--	View →

Side Effects

GI discomfort at high doses (diarrhea)
Insomnia at very high doses (paradoxical in some individuals)

Drug & Supplement Interactions

Growth hormone secretagogues — ornithine may stimulate GH release
Arginine supplements — metabolic interaction (urea cycle)

Always inform your healthcare provider about all supplements you take.

Related Ingredients

Taurine

Quick Facts

Dosage: Sleep: 400-800 mg, 30-60 min before bed
Forms: capsule powder
Natural Sources: Meat, Fish, Dairy, Eggs
Upper Limit: Not formally established; 6,000 mg/day used in exercise studies
Best Time: 30-60 minutes before bed on an empty stomach

Evidence Summary

Shift Work Sleep Disorder C

Insomnia C

FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.