What is L-ornithine? – Benefits & Dosage


There is a non-essential amino acid known as L-ornithine, which is necessary for the production of protein, enzymes, polyamines, creatine and muscle tissue. As a key component of the urea cycle, Ornithine manages the disposal of excess nitrogen in the form of ammonia. In addition to boosting growth hormone production, ornithine supplements are also claimed to help burn fat.

 Urea and L-ornithine are synthesized by the liver using arginase and L-arginine during the urea cycle. E. coli makes L-ornithine from L-glutamate in the intestines. L-ornithine is an extremely valuable precursor to numerous other highly valuable compounds, including glutamic acid, proline, and citrulline. Connective tissues such as the skin contain high levels of L-ornithine. 

Benefits of Ornithine – What does it do?

Wound Healing

It has been shown that supplementing with Arginine enhances wound healing, in particular collagen synthesis. There are many similarities between the biopharmacological effects of Ornithine and that of Arginine in the urea cycle. The present study examines the effects of ornithine supplementation on wound healing and describes its possible mechanism. Effects of Ornithine on wound healing

Results of the study showed that ornithine supplementation enhanced wound healing in mice and increased collagen deposition in the wound bed.

Decrease Blood Pressure

The body uses Ornithine to make Arginine, which is then converted into nitric oxide. Nitric oxide stimulates the blood vessels to dilate, which results in increased circulation and blood flow. The dilation or relaxing of the blood vessel walls causes a decrease in blood pressure, according to a study done to evaluate the antihypertensive effect of L-Arginine in patients with mild hypertension. Blood pressure in the test group given 12 grams of Arginine dropped significantly. Even though this study looked at Arginine, it is still relevant because Ornithine is used by the body to make Arginine, and supplementing with Ornithine has been shown to elevate Arginine levels in the body. 

Eliminates Ammonia

Protein metabolism produces ammonia as a byproduct. Because ammonia is toxic, the body neutralizes and eliminates it through the urea cycle.

The enzymes that are necessary for the proper functioning of the urea cycle contain Ornithine. In spite of the fact that urea cycle disorders are often caused by genetic factors, a deficiency of Ornithine in response to illness or stress can cause a small rise in blood ammonia levels.

Stimulate growth hormone

Many athletes and bodybuilders take ornithine supplements since they can stimulate the release of growth hormone, an anabolic hormone that burns fat and increases muscle mass. One study looked at the growth hormone stimulating effect of large oral doses of Ornithine. Three female bodybuilders and nine male bodybuilders participated in the study. Blood levels of Ornithine were significantly higher at 45 and 90 minutes regardless of dosage. The effect of ornithine ingestion on blood levels of growth hormone was not significant until 90 minutes after oral administration of the highest dosage of 170 mg per kg. The study referenced can be found here: Ornithine ingestion and growth hormone release in bodybuilders.

Increases Endurance and delays fatigue

Researchers looked at the effect that administration of oral Ornithine would have on fatigue. A double-blind study was conducted using 17 healthy test subjects. The subjects were split into two groups: the placebo group and the Ornithine group. In the Ornithine group, they received 2g per day for 7 days and then 6g for 1 day. Both groups’ endurance and fatigue threshold was tested using a cycle ergometer.

In the Ornithine group, the researchers found that the subjective feeling of fatigue was significantly reduced. Subjective fatigue levels decreased significantly when compared to placebo. This study suggests that l-ornithine has a significant antifatigue effect through boosting the efficiency of energy consumption and enhancing the excretion of ammonia. The referenced study can be found at Ornithine supplementation attenuates physical fatigue.

Ornithine side effects

The information on potential side effects is scarce. There has not been much research on the side effects of L-Ornithine to provide us with any reliable insight into potential side effects. Anecdotally, some users report the following side effects:

  • Nausea
  • Vomiting
  • Stomach upset
  • Diarrhea
  • Insomnia
  • restlessness

The above side effects are usually seen when large dosages are taken orally. It is recommended that you start with small dosages and work your way up to larger ones if you are able to tolerate it and do not experience any gastro upset side effects. Because Ornithine can increase nitric oxide in the body, it can potentially cause changes in blood pressure, so it is important to consult your doctor before starting any Ornithine supplements.

Dosage of Ornithine

Most of the research studies looking at the athletic, health and muscle-building benefits of Ornithine have used dosages that range from 2 to 5 grams per day taken orally. Some studies have used much larger doses approaching 10 grams per day, but these high doses tend to increase gastrointestinal side effects such as diarrhea and stomach upset.

Sources of Ornithine

Animal Sources

  • Meat
  • Fish
  • Diary
  • Eggs

Plant Sources

  • Rice
  • Oats
  • Wheat
  • Coconuts
  • Soybeans
  • Caron
  • Nuts


Effect of Supplemental Ornithine on Wound Healing – ScienceDirect

Evaluation of the antihypertensive effect of L-arginine supplementation in patients with mild hypertension assessed with ambulatory blood pressure monitoring – PubMed (nih.gov)

Ornithine ingestion and growth hormone release in bodybuilders – ScienceDirect

l-Ornithine supplementation attenuates physical fatigue in healthy volunteers by modulating lipid and amino acid metabolism – ScienceDirect

Ornithine – Wikipedia

The information contain within this article is not to be considered health or medical advice. Always consult your doctor prior to taking any supplements.