L-Citrulline
An amino acid that supports nitric-oxide production and blood flow.
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What it is
L-citrulline is an amino acid the body converts to arginine and then nitric oxide, supporting blood-vessel dilation. It's popular in pre-workout products.
How it works
L-citrulline is an amino acid the body converts to arginine and then to nitric oxide, which relaxes blood vessels and improves blood flow. Because it raises blood arginine more effectively than arginine itself, it's popular in pre-workout products for 'pump' and performance.
What it's been studied for
Taken to support blood flow, exercise performance, and 'pump,' and studied for circulation.
What the evidence shows
Some studies suggest citrulline can modestly improve exercise performance and reduce muscle soreness; results are mixed and effect sizes are small.
Who should consider it
It's used mainly by people wanting better blood flow, exercise performance, and reduced muscle soreness, and it's studied for circulation. Effects are modest, so expectations should be realistic.
Amounts commonly studied
Studies commonly use around 6-8 g of citrulline malate before exercise, or 3 g of pure L-citrulline.
How to take it
Studies commonly use around 6-8 g of citrulline malate before exercise, or about 3 g of pure L-citrulline. It's taken pre-workout and mixes easily into a drink.
Forms & absorption
L-citrulline or citrulline malate (bound to malic acid). It's better than arginine for raising blood arginine levels.
Food sources
Watermelon is the standout natural source (its rind is especially high); smaller amounts are in other cucurbits like cucumber and melon.
Safety & interactions
Generally well tolerated. May add to the blood-pressure-lowering effect of certain medications, so check with a provider if that applies.
Myths & what it won't do
Myth: citrulline dramatically boosts strength. Reality: any performance and soreness benefits are modest and inconsistent. Myth: arginine is just as good. Reality: citrulline actually raises blood arginine more reliably than taking arginine directly.
Common questions
- Citrulline or arginine?
- Citrulline raises blood arginine and nitric oxide more effectively than arginine itself, so it's often preferred for that goal.
- How much and when?
- Commonly 6-8 g of citrulline malate (or ~3 g pure) taken before exercise.
- Any cautions?
- It may add to the blood-pressure-lowering effect of some medications — check with your provider if that applies.
The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.
Related goals
Research on L-Citrulline
Recommendations on this page are informed by published research. This is educational information, not medical advice.
- Trexler ET, Persky AM, Ryan ED, et al. Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis. Sports Med. 2019;49(5):707-718. View study →Note: Found a small but significant improvement in high-intensity strength and power performance.