L-Ornithine is a free amino acid, meaning it is not incorporated into proteins but instead performs its own metabolic functions in the body. It is naturally synthesised by the body from L-Arginine, through the action of the enzyme arginase. Its main role lies in the urea cycle, a metabolic pathway located in the liver that converts toxic ammonia into urea, a water-soluble molecule easily eliminated by the kidneys. Ammonia is a metabolic waste product generated during the breakdown of proteins and amino acids; its build-up in the blood can cause tiredness, difficulty concentrating and general discomfort. Although the body can synthesise ornithine itself, in situations of intense metabolic stress — sustained physical effort, a high-protein diet, a detox period — needs can exceed the body’s own production capacity, justifying supplementation.

The urea cycle (or ornithine cycle) is a series of enzymatic reactions occurring in liver cells (hepatocytes) that convert ammonia, highly toxic to the nervous system, into urea, a harmless molecule eliminated through urine. L-Ornithine is both the starting point and the end point of this cycle. By supplementing with L-Ornithine, more substrate is provided to the urea cycle, which can optimise the rate of ammonia-to-urea conversion — a property particularly sought after by athletes doing intense training, where muscle protein breakdown generates significant amounts of ammonia.

Ornithine is taken by many athletes for its effects on muscle recovery and management of post-exercise fatigue. During intense physical exercise, the body breaks down muscle protein, generating ammonia; the build-up of this ammonia in the blood is linked to central fatigue, a mechanism that reduces performance and lengthens recovery time. By supporting ammonia elimination via the urea cycle, L-Ornithine helps reduce this fatigue and speed up recovery between training sessions. L-Ornithine is also linked to growth hormone (GH) production; some publications suggest that ornithine supplementation, particularly taken before bed, may support nocturnal GH secretion, a hormone involved in tissue repair and overall recovery. L-Ornithine is also increasingly studied for its impact on sleep quality — some people report falling asleep faster and sleeping more deeply when taking ornithine in the evening, away from meals.

The recommended dose is 2 capsules per day (1,000 mg of L-Ornithine), ideally taken on an empty stomach or between meals, with a large glass of water. For sports recovery, it is common to take the capsules before bed. The 120-capsule bottle represents 60 days of course at 2 capsules per day. The vegetable capsules (hypromellose) suit vegetarians.

Pregnant or breastfeeding women and people under medical treatment should consult their healthcare professional before use.

What is the difference between ornithine and arginine?

Ornithine and arginine are two amino acids metabolically linked in the urea cycle. Arginine is the direct precursor of nitric oxide (NO), a vasodilator, while ornithine is more involved in ammonia detoxification. The two are often combined for synergistic effects, particularly in sports supplementation.

When should I take ornithine for sleep?

For an effect on sleep quality, it is recommended to take the ornithine capsules about 30 to 60 minutes before bed, on an empty stomach or away from dinner. This evening dose supports the elimination of ammonia accumulated during the day and supports nocturnal growth hormone secretion.

Is ornithine suitable for vegetarians?

Yes. The Ornithine Now Foods capsules are vegetable-based, made of hypromellose. The excipients are also of plant origin, making this supplement suitable for vegetarians.

Herba Barona is an independent specialist supplement shop in the heart of Paris — established in 2006. What you order is genuinely on our shelves: we ship from our own stock, with no dropshipping and no long waits.

Visit us at 10 rue Théophile Roussel, Paris 12 — or use Click & Collect and pick up your order in-store. We also deliver across France and Europe. Friendly, expert advice in English from our team.

Where is the shop?

Herba Barona is at 10 rue Théophile Roussel, 75012 Paris — a two-minute walk from Ledru-Rollin (line 8), close to Bastille. Open Tuesday to Saturday, 9:30 am–6:30 pm.

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Yes. We ship across France and Europe under the same conditions as our French store, or choose Click & Collect to pick up your order for free at our Paris shop.