L-Citrulline: What Is It, Its Benefits and Dose? 6 Facts About the Amino Acid That Becomes Arginine

L-Citrulline: The Amino Acid First Found in Watermelon

L-citrulline has become one of the best-known ingredients in pre-workout supplements, often described as better than arginine itself at boosting nitric oxide. What is it, and what does the research actually show? This article answers in 6 short facts.

1. What Is L-Citrulline?

L-citrulline is a non-essential amino acid, meaning the body makes its own, mostly in the gut. Its name comes from watermelon – Citrullus in Latin – where it was first identified, and the white rind is one of the richest sources. Unlike most amino acids, citrulline is not used directly to build proteins.

2. How Does It Work?

The kidneys convert citrulline into arginine, which the body uses to make nitric oxide, a molecule that helps blood vessels relax. Interestingly, oral L-citrulline can raise blood arginine more efficiently than arginine itself, because it is not broken down as heavily in the gut and liver. See arginine vs citrulline for details.

3. What Does Research Show for Exercise?

Some studies found that 6 to 8 g of citrulline malate taken about an hour before training increased repetitions in resistance exercise and reduced fatigue in some athletes. Results are not consistent across studies, though, and any benefit tends to be modest – training, nutrition and sleep still matter most.

4. L-Citrulline or Citrulline Malate?

• L-citrulline: pure citrulline; studies typically used 3 to 6 g a day.
• Citrulline malate: citrulline bound to malic acid; 8 g provides roughly 4 to 5 g of citrulline.

When comparing products, look at the actual amount of citrulline, not just the weight of the compound.

5. Other Uses

Small studies have looked at 1.5 g of L-citrulline daily in men with mild erectile dysfunction and found improvement in some. The research is limited, citrulline is not a treatment for ED, and the issue deserves a medical assessment because it can signal heart disease or diabetes.

6. Safety and Precautions

• Most healthy people tolerate it well; it can cause mild stomach upset.
• It may lower blood pressure slightly, so people on blood pressure medicines should check with their doctor.
• Do not combine it with nitrates or ED medicines without advice.
• For adults; pregnant and breastfeeding women should ask a doctor first.

Natural Sources of L-Citrulline

Watermelon is the best-known source, especially the white part near the rind, with smaller amounts in cucumber, pumpkin and melon. Food amounts are far below study doses, which is why athletes use supplements.

L-Citrulline With Arginine

Some products pair citrulline with arginine, supplying arginine both directly and through citrulline. One example is NOW Arginine and Citrulline, with 500 mg of arginine and 250 mg of citrulline per capsule. For more on arginine, read L-arginine benefits and L-arginine dosage.

How to Take L-Citrulline

For exercise, studies usually gave a single dose about an hour before training, while daily use spreads the dose across the day. Take it with water, with or without food, and start at the lower end of the range to see how your stomach responds. Taking L-citrulline consistently for several weeks gives a fairer picture than a single dose.

L-Citrulline FAQ

When should I take L-citrulline?

In exercise studies it was usually taken about an hour before training.

Is L-citrulline a stimulant?

No. It contains no caffeine and does not stimulate the nervous system.

Does it cause insomnia?

Not known to – unlike pre-workouts that contain caffeine.

Does it really raise nitric oxide?

It raises arginine, from which nitric oxide is made – read nitric oxide supplements.

Can women take L-citrulline?

Yes, adult women can use it the same way, though pregnant and breastfeeding women should ask a doctor first.

Conclusion

L-citrulline is an amino acid that converts efficiently into arginine, with encouraging but inconclusive research on exercise performance. Mind the difference between L-citrulline and citrulline malate, and talk to your doctor if you take blood pressure medicines. You can find NOW Arginine and Citrulline at No Style Like pharmacy.

This article was reviewed by the No Style Like pharmacy content team. It is for general awareness only. Arginine and citrulline are dietary supplements, not medicines intended to diagnose or treat any disease, and this article does not replace medical advice.

Do not exceed the dose on the label without advice. Ask your doctor before use if you take blood pressure medicines, nitrates, heart medicines or erectile dysfunction medicines. For more information see the MedlinePlus L-arginine page.