In this article
A clinically studied ingredient is a starting point. The form, daily amount, duration, participants and measured outcome all matter. The protocols below describe research; they are not instructions to increase your dose.
L-citrulline and erections
A small single-blind pilot gave 24 men with mild erectile dysfunction 1.5 g daily for one month, after a placebo month. Its erection-hardness finding is preliminary, with a small sample and fixed treatment order. It does not establish that 4 g works better, or validate a combination product.
Cormio and colleagues, 2011 ↗L-citrulline and blood markers
A crossover study tested several regimens, including 3 g twice daily. That higher regimen increased arginine and some nitric-oxide-related markers, but no treatment improved flow-mediated dilation over baseline. A change in a marker is not automatically a clinical benefit.
Schwedhelm and colleagues ↗Nitrosigine and citrulline malate
A randomized crossover study in 24 healthy young adults compared a single 1.5 g Nitrosigine dose, 8 g citrulline malate and placebo. Both active conditions increased flow-mediated dilation. This was an acute vessel-function study, not evidence of better long-term sexual or cardiovascular outcomes in men over 40.
Rogers and colleagues, 2020 ↗What to do with those numbers
Match like with like. Nitrosigine weight is not pure arginine weight; citrulline malate is not pure L-citrulline; a proprietary blend is not an individual dose. If the form or amount is missing, the study match remains unresolved.
NIH characterizes the exercise evidence for citrulline as limited and conflicting. One favorable study should not stand in for the full body of evidence.
NIH exercise-supplement evidence ↗For general education, not diagnosis or treatment. If you take medicines or have a health condition, have a clinician or pharmacist review the exact formula before use.