Ingredient
Moderate evidenceL-Citrulline
Also known as: citrulline, citrulline malate
The pump and blood-flow ingredient with real evidence — when it is dosed properly.
What it is
Citrulline is an amino acid that the body converts into arginine and then nitric oxide, which widens blood vessels. It comes as pure L-citrulline or as citrulline malate (citrulline bound to malic acid). It is the ingredient behind the "pump" claim on most pre-workout labels.
How it works
By raising nitric oxide, citrulline improves blood flow to working muscles, which can enhance the training pump and may modestly reduce fatigue and muscle soreness. The evidence is reasonable but not overwhelming, and it depends entirely on getting a real dose rather than the token sprinkle many products use.
Effective dose
Aim for 3 to 6g of pure L-citrulline, or 6 to 8g of citrulline malate (which is only part citrulline), taken 30 to 60 minutes pre-workout. A huge number of pre-workouts list citrulline but dose it well below this, which is exactly the kind of under-dosing our scoring penalises.
Safety and upper limit
Citrulline is well tolerated even at higher doses, with no meaningful safety concerns for healthy people. It is gentler on the stomach than arginine, which is one reason it has largely replaced it in modern formulas.
Where you find it
Pre-workouts, pump/nitric-oxide products and some intra-workout drinks.
Top Pre-Workout picks
The highest-scoring products in the category where L-Citrulline matters most.
Frequently asked
How much citrulline should a pre-workout have?
Around 3 to 6g of pure L-citrulline, or 6 to 8g of citrulline malate. Many products under-dose it well below this.
Is L-citrulline or citrulline malate better?
Both work. Citrulline malate is only part citrulline by weight, so you need a higher total to match the same pure L-citrulline dose.
Does citrulline actually give a pump?
It can, by raising nitric oxide and blood flow, but only at a proper dose. Under-dosed citrulline does little.
L-Citrulline vs ...
Related guides
This page is educational and not medical advice. Doses are general guidance from the published research, not a personal prescription. Before starting any supplement that could affect a medical condition or interact with medication, speak to a qualified clinician.