Independent supplement ratingsUS and Canada · Updated weekly
A ratings desk for a category that has spent thirty years grading its own homework.
A ratings desk for a category that has spent thirty years grading its own homework.
L-citrulline raises nitric oxide more effectively than taking arginine directly (arginine is poorly absorbed), which is why it's the better-evidenced choice for blood flow and exercise performance. In the men's category, it's the single ingredient with a real leg to stand on.
The catch is dose: the studied range is high — roughly 3,000–6,000 mg of citrulline a day — and most 'male enhancement' pills contain a fraction of that, hidden in a proprietary blend. A plain citrulline powder gets you a real dose for a fraction of the price of the branded pills.
The effect is modest and it's a supplement, not a treatment — anything medical is a conversation for a clinician. Research on PubMed →
Citrulline malate is citrulline bound to malic acid, usually in a 2:1 ratio. That matters for the dose: a 3 g serving of citrulline malate 2:1 delivers roughly 2 g of citrulline, not 3. Check the label against the studied range of 3,000–6,000 mg of citrulline, taking two thirds of the malate figure.
The performance trials typically dose it around an hour before training, which fits how long plasma arginine takes to rise after an oral dose. Longer-term daily use has also been studied. What matters more than the timing is the amount: under a gram is decorative.
For raising blood arginine, yes — which is the strange part. Oral arginine is largely broken down by an enzyme in the gut wall before it reaches circulation. Citrulline passes through intact and is converted afterwards, and in a head-to-head crossover trial it raised plasma arginine more effectively than arginine itself. The detail is in this piece.
Reviewed by the NFS editorial team · Educational only — not medical advice.