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AMINO ACIDS

L-Ornithine

Sleep quality · stress · ammonia clearance

MODERATE EVIDENCEVEGANREAD THE RESEARCH
Written to our editorial standards · reviewed against published research· Updated 5 Jun 2026
Last reviewed: May 30, 2026
QUICK ANSWER

L-Ornithine: Sleep quality · stress · ammonia clearance. An amino acid that helps clear ammonia and has been shown to lower stress and improve sleep quality. Standard dose 2,000-4,000 mg, taken in the evening, about $16/month. Evidence rating: moderate evidence.

Where to buy

NOWFOODSL-Ornithine 500 mg120 VEG CAPSDIETARY SUPP.
RECOMMENDED
NOW Foods, L-Ornithine
2,000-4,000 mg · Evening · ~$16/month

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All product options

NOWFOODSL-Ornithine 500 mg120 VEG CAPSDIETARY SUPP.BESTSELLER
L-Ornithine 500 mg
NOW Foods
120 veg caps · $16 · ★ 4.7
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JARROWFORMULASL-Ornithine100 CAPSULESDIETARY SUPP.BEST VALUE
L-Ornithine
Jarrow Formulas
100 capsules · $14 · ★ 4.6
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SOLGARL-Ornithine 500 mg50 VEG CAPSDIETARY SUPP.PREMIUM
L-Ornithine 500 mg
Solgar
50 veg caps · $13 · ★ 4.6
Buy on iHerb →Buy on Amazon →
NUTRICOSTL-Ornithine180 CAPSULESDIETARY SUPP.PREMIUM
L-Ornithine
Nutricost
180 capsules · $18 · ★ 4.6
Buy on iHerb →Buy on Amazon →

What is L-Ornithine?

L-ornithine is a non-protein amino acid central to the urea cycle, the body's system for clearing ammonia. Because rising ammonia contributes to fatigue and poor sleep, supplemental ornithine has been studied for stress and sleep: a controlled trial found that 400 mg daily reduced cortisol and improved sleep quality and next-day fatigue in stressed adults, while higher doses are used by athletes to buffer exercise-induced ammonia. It is often paired with arginine. Doses range from 400 mg for stress and sleep up to 2 to 4 g for athletic use, taken in the evening or after exercise.

WHY IT MATTERS

An amino acid that helps clear ammonia and has been shown to lower stress and improve sleep quality.

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Common questions

What is L-Ornithine?
L-ornithine is a non-protein amino acid central to the urea cycle, the body's system for clearing ammonia. Because rising ammonia contributes to fatigue and poor sleep, supplemental ornithine has been studied for stress and sleep: a controlled trial found that 400 mg daily reduced cortisol and improved sleep quality and next-day fatigue in stressed adults, while higher doses are used by athletes to buffer exercise-induced ammonia. It is often paired with arginine. Doses range from 400 mg for stress and sleep up to 2 to 4 g for athletic use, taken in the evening or after exercise.
What is L-Ornithine used for?
Sleep quality · stress · ammonia clearance. An amino acid that helps clear ammonia and has been shown to lower stress and improve sleep quality.
What is the standard dose of L-Ornithine?
2,000-4,000 mg, typically taken in the evening. Approximate cost is $16 per month.
How strong is the evidence for L-Ornithine?
Moderate evidence for its primary uses. See the full study list on the research page.

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