Taking a specific amount of citrulline powder every day for a week makes certain amino acids go up in your blood, but it doesn’t change how your body builds or breaks down protein when you haven’t just eaten.

Taking a specific amount of citrulline powder every day for a week can raise levels of certain amino acids in your blood, but it doesn’t change other important blood or urine markers like insulin or albumin.

Taking citrulline pills every day for a week at a specific dose doesn't help your body hold onto more protein, even if you're healthy and eating well.

Taking a specific amino acid called L-citrulline twice a day for a week boosts a related chemical in your blood more than taking that chemical directly, which might help your body make more of a molecule that relaxes your blood vessels.

Taking a specific amino acid supplement called L-citrulline every day for a week, then taking one more dose an hour before a short, intense bike ride, helps trained male cyclists finish the ride 1.5% faster.

Taking a specific amino acid called L-citrulline twice a day for a week helps raise levels of another amino acid, L-arginine, in the blood more than taking L-arginine directly—this might help your body make more nitric oxide, which is good for blood flow.