Supplements

L-citrulline

By Cameron McClevePublished Sep 26, 2026Updated Sep 27, 20263 min read

What is it?

L-citrulline is an amino acid your body makes naturally and that is also found in foods such as watermelon. In supplements, it appears as pure L-citrulline or as citrulline malate, which combines citrulline with malate. It is commonly included in pre-workouts for blood-flow support and possible improvements in exercise performance. [1,3,4]

How does it work?

Your body converts citrulline into arginine, an amino acid used to produce nitric oxide. Nitric oxide helps the smooth muscle in blood-vessel walls relax, allowing the vessels to widen. This is the pathway behind citrulline's use as a pump ingredient. [1]

In a seven-day controlled human study, twice-daily citrulline raised circulating arginine and, at the highest tested dose, increased markers of nitric-oxide signaling. This establishes a real biological effect, although a rise in those markers does not guarantee a noticeable workout benefit. [1]

Why is it in pre-workout?

Blood flow and pump

Citrulline is included to support blood flow and potentially enhance the full, tight feeling of a muscle pump during training. A small, placebo-controlled study in 21 adults found that 8 g of citrulline malate improved an artery's dilation response one hour after taking it. The measurement was made at rest, so it supports a vascular effect without directly proving a bigger lifting pump. [2]

Direct workout findings are mixed. In another controlled study, 18 trained adults took 8 g of pure L-citrulline before bench pressing. Participants felt a pump in both conditions, with no extra perceived pump or muscle-oxygenation benefit detected from citrulline in this small trial. This helps set expectations: some people may value the blood-flow support even when a bigger pump is not noticeable. [3]

Possible help with repeated effort

Another reason for including citrulline is the possibility of completing more work before fatigue. A 2026 meta-analysis combining 30 citrulline-malate trials found a small average improvement across exercise-performance outcomes. Results varied, and the lifting-endurance and strength/power analyses did not establish a clear benefit. The authors rated the evidence low to very low certainty. [4]

The practical expectation is a possible small workout benefit. These findings do not establish additional long-term muscle growth. Citrulline's role is in blood-flow support and potential performance benefits; it does not supply the stimulant effect of caffeine. [1,3,4]

PRACTICAL AMOUNT

How much?

6–8 g

FORM & SCHEDULE

What it refers to

pure L-citrulline about 60 minutes before training

This is a practical range, not a proven best dose. The mixture calculation assumes the labeled ratio is accurate. Do not take extra scoops of a mixed pre-workout just to reach the citrulline amount.

6–8 grams — L-citrulline

Read detailed dosing notes

About 60 minutes before training. [3,5]

Only the citrulline portion counts toward the L-citrulline amount. For a 2:1 ratio by weight, multiply the total mixture by 2/3.

6 grams of citrulline malate (2:1 ratio) = 4 grams L-citrulline + 2 grams of malate.

6–8 g is a practical pre-workout range, not a proven minimum or optimal dose. These studies do not establish that 8 g works better than 6 g. The conversion above calculates ingredient content; it does not establish equal effects between formulations. Use the label's declared L-citrulline amount when available; the 2/3 calculation assumes an accurate ratio by weight. [3,4,5]

Count citrulline already in your pre-workout before adding more. Avoid extra servings of a mixed pre-workout just to reach this amount, since that also increases its other ingredients. Stop if it causes discomfort; check with a clinician or pharmacist if you take medication or have a medical condition.

Sources & further reading