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L-Ornithine

Sleep quality · stress · ammonia clearance

Moderate evidenceVegan47 studies on PubMedRead the research
Written to our editorial standards · reviewed against published research· Updated 30 May 2026
Last reviewed: May 30, 2026

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

NOW Foods L-Ornithine 500 mg
Recommended
NOW Foods, L-Ornithine
2,000-4,000 mg · Evening · ~$16/month

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All product options

NOW Foods L-Ornithine 500 mgBestseller
L-Ornithine 500 mg
NOW Foods
120 veg caps · $16 · ★ 4.7
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Jarrow Formulas L-OrnithineBest Value
L-Ornithine
Jarrow Formulas
100 capsules · $14 · ★ 4.6
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Solgar L-Ornithine 500 mgPremium
L-Ornithine 500 mg
Solgar
50 veg caps · $13 · ★ 4.6
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Nutricost L-OrnithinePremium
L-Ornithine
Nutricost
180 capsules · $18 · ★ 4.6
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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.

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

Best for your goal

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Taurine
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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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