Citrulline Malate

Supplements · Sports Performance · Supplement, Typed Supps

Your body turns it into the amino acid that widens blood vessels.

Stage by stage

Intake (Powder): Absorbed efficiently, actually raising blood arginine more effectively than taking arginine directly.
Small intestine (Efficient absorption): Absorbed efficiently in the small intestine, raising blood arginine levels more effectively than taking arginine directly.
Kidneys (Converted to arginine): Converted in the kidneys into arginine.
Blood vessels (Widens blood vessels): Arginine is used to produce nitric oxide, increasing blood flow to working muscles.

What the evidence supports

Increasing training volume and reducing muscle soreness — moderate evidence. Several trials report more reps to failure and less soreness, typically with citrulline malate at 6–8 g taken an hour before training. Effect sizes are modest.
Raising nitric oxide and blood flow — moderate evidence. It raises plasma arginine more effectively than arginine itself does, which is the mechanism. The biochemistry is well established.
Improving endurance performance — limited evidence. Inconsistent across trials.

Typical dose

6–8 g of citrulline malate an hour before training

Upper limit: No formal UL. Doses from 2 g to 15 g have been given to healthy adults without adverse effects on blood chemistry, and a tolerance study put the no-observed-adverse-effect level at 24 g daily for four weeks — the 6–8 g used in training trials sits well below that

Timing

30–60 minutes before exercise.

Time to effect

~1 hr: Acute blood-flow effect studied in most research.

Medication interactions

PDE5 inhibitors for erectile dysfunction (sildenafil, tadalafil): Both work through the nitric oxide–cGMP pathway, so the blood-pressure-lowering effects can add up. Citrulline's own effect is small — a few mmHg in trials — so this is a caution rather than a prohibition, but the combination has not been studied and light-headedness is the thing to watch for. (moderate)
Nitrates (glyceryl trinitrate, isosorbide mononitrate): Same mechanism, and nitrates are the drug class where nitric-oxide stacking causes real problems. There are no trials of the combination; if you are prescribed a nitrate, ask your doctor before adding citrulline. (moderate)
Blood pressure medication generally: Citrulline modestly lowers systolic and diastolic blood pressure in trials, so it may add to whatever your medication is already doing. Worth checking your readings when you start rather than avoiding it. (moderate)

Common myth

“Citrulline is basically the same as arginine.” In reality: Taking citrulline raises blood arginine more effectively than arginine supplements themselves, due to gut and liver processing.

Food sources

Watermelon — Fruit