Last Updated: September 28 2022

L-Citrulline, or simply just citrulline, is a nonessential amino acid. It is efficiently turned into L-arginine in the kidneys after supplementation, which makes it a good choice for increasing nitric oxide synthesis in the body.

Citrulline is most often used for

What is citrulline?

Citrulline is one of the three dietary amino acids in the urea cycle (the other two are L-arginine and L-ornithine. Taking citrulline increases plasma levels of ornithine and arginine and improves the ammonia recycling process and nitric oxide metabolism. Consequently, citrulline may be useful in situations in which nitric oxide is relevant, such as athletic performance, vascular health, and erectile dysfunction. There are very few foods that have useful amounts of citrulline, but watermelon is a notable exception.

What are citrulline’s main benefits?

A considerable amount of research suggests that chronic supplementation with citrulline mildly reduces blood pressure and mildly improves blood flow, particularly in individuals with hypertension or other cardiovascular problems. Limited research suggests that supplementation with citrulline, both short-term and long-term, can reduce fatigue, increase power output, and improve endurance in both aerobic and anaerobic exercise. More research is needed for citrulline’s potential effects on erectile dysfunction, but a small amount of research suggests a beneficial effect.

What are citrulline’s main drawbacks?

Although the safety of long-term supplementation with high doses of citrulline warrants further investigation, research to date suggests that it is well tolerated in most individuals. Unlike arginine and ornithine, high doses of citrulline don't seem to result in gastrointestinal distress.

How does citrulline work?

Citrulline supplementation increases the body’s arginine levels. Because arginine is the main substrate for the synthesis of nitric oxide, citrulline ingestion can indirectly increase nitric oxide production. In turn, given the role of nitric oxide in vasodilation, mitochondrial respiration, calcium handling, and glucose uptake, greater amounts of nitric oxide can improve circulatory health and muscle function and reduce fatigue.

What else is Citrulline known as?
Note that Citrulline is also known as:
  • L-Citrulline
  • Stimol (Brand Name)
  • Watermelon extract
Dosage information

To supplement L-citrulline for circulatory health or to alleviate erectile dysfunction, take 2,000 mg of citrulline, three times a day with meals, for a total daily dose of 6,000 mg. L-citrulline does not need to be taken with meals, however.

To supplement for circulatory health with a citrulline malate supplement, take 1.76 g of citrulline malate for every 1 gram of citrulline you would normally take.

To supplement L-citrulline to enhance sports performance, take 6,000 – 8,000 mg of citrulline malate about an hour before exercise. On days that you don't exercise, it can be broken up into smaller doses.

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