L-Citrulline: Uses, Benefits, Dosage & Safety

Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

Quick summary

L-citrulline is an amino acid that the body converts into arginine — and it raises nitric oxide more effectively than taking arginine directly. It has modest evidence for blood pressure, blood flow and exercise.

What is L-Citrulline?

L-citrulline is an amino acid found naturally in watermelon and made by the body. Although L-arginine is the direct precursor to nitric oxide, citrulline is converted into arginine in the kidneys and, perhaps counterintuitively, raises blood arginine levels more reliably than swallowing arginine itself. It is sold as plain L-citrulline or as 'citrulline malate' (bound to malic acid), and is marketed for circulation, blood pressure, erectile function and exercise performance.

What L-Citrulline is commonly used for

L-Citrulline is used in supplements as nutritional support, not as a treatment for any medical condition.

How L-Citrulline works

Because citrulline bypasses the gut and liver breakdown that limits oral arginine, it produces a more sustained rise in arginine and therefore in nitric oxide, the molecule that relaxes and widens blood vessels. Improved blood flow is the basis for its use in blood pressure, erectile function and exercise. This better conversion is the main reason some people prefer citrulline over arginine.

What the evidence says

Here's an honest snapshot of what published research suggests about L-Citrulline — including where the evidence is limited.

Trials suggest L-citrulline can modestly lower blood pressure and improve markers of blood-vessel function. (PubMed research)
Citrulline malate has shown small benefits for exercise performance and reduced muscle soreness in some studies. (PubMed research)
Small studies report possible benefit for erectile function, with preliminary results. (PubMed research)

Typical dosage used in studies

Studies commonly use about 3-6 g/day of L-citrulline, or roughly 6-8 g of citrulline malate for exercise. This is research information, not a recommendation.

Side effects and safety

L-citrulline is generally well tolerated and tends to cause less digestive upset than L-arginine. Reported side effects are mild.

Medication interactions and who should avoid L-Citrulline

Medication & safety check

Because it can lower blood pressure, people on blood-pressure medication or erectile-dysfunction drugs (such as PDE5 inhibitors) should be cautious about additive effects and check with a doctor. Pregnancy and breastfeeding data are limited.

This is general information, not personal medical advice. If you take any medication, confirm it's safe to combine with L-Citrulline with your doctor or pharmacist first.

Sources & further reading

The evidence summary above is drawn from these sources. For general, authoritative background you can also consult:

Frequently asked questions

Is citrulline better than arginine?

For raising nitric oxide, often yes — citrulline avoids the gut-and-liver breakdown that limits oral arginine, so it raises arginine levels more reliably.

What is L-citrulline good for?

Modest benefits for blood pressure, blood-vessel function, and (as citrulline malate) exercise performance and soreness.

Plain citrulline or citrulline malate?

Plain L-citrulline (3-6 g) is common for blood flow; citrulline malate (6-8 g) is more often used for exercise.

Is it safe?

Generally yes, with less stomach upset than arginine. The main caution is additive blood-pressure lowering with certain medications.

Can it help erections?

Small studies suggest a possible modest benefit, but the evidence is preliminary.