Citrulline
Citrulline raises blood arginine and with it nitric oxide production. At 6 to 8 grams, taken 40 to 60 minutes before training, that yields around three extra repetitions on average. For endurance, two independent meta-analyses found no effect.
What the research shows
Shown, with a clear condition or a limited scope.
Vårvik (2021) pooled eight double-blind studies with 137 participants and saw an average of three extra repetitions to failure after 6 to 8 grams of citrulline malate, a small effect (SMD 0.196) that stayed at the level of a tendency in the lower body subanalysis. Endurance looks different: Viribay (2022) found no effect on aerobic performance, perceived exertion or oxygen uptake across ten studies, and Harnden (2023) found no difference in time to exhaustion across nine studies with 158 participants. None of these meta-analyses reports a manufacturer interest. That is why the level stays at reasonable: there is repeated human evidence, with a small effect that shows up only in strength training.
Who it makes sense for: Strength athletes who want a few extra repetitions per set and take 6 to 8 grams, the amount that was studied. Endurance athletes gain nothing from it according to two meta-analyses.
How we weigh evidenceClinical dosage
Origin
Natural & syntheticNamed after watermelon (Citrullus lanatus), where it naturally occurs. Also found in cucumber and pumpkin. In supplements usually synthetically produced as L-citrulline or citrulline malate.
Safety
Citrulline malate is well tolerated up to 10 grams. Some people get stomach upset at higher doses. The strength effect is small and consistently measured across several studies. Single studies reporting much larger effects are not reproduced by the meta-analyses.
For comparison
To get 3g of citrulline from watermelon, you'd need to eat over 3 pounds of watermelon. That's why supplements are much more practical for sports dosages.
Dosage by weight and gender
The effective citrulline dose for sports performance is 6-8g L-citrulline or 8-10g citrulline malate per session (Gonzalez & Trexler, 2020). Body weight plays a limited role since the effect is local in blood vessels. There are no meaningful differences between men and women. With citrulline malate, about 55% is actual citrulline, so you need a higher dose than pure L-citrulline.
Frequently asked questions
What is citrulline?
Citrulline is an amino acid your body converts to arginine, which boosts nitric oxide (NO) production. This widens your blood vessels so more blood and oxygen reach your muscles.
Is citrulline dangerous?
No. Citrulline is one of the safest pre-workout ingredients. Doses up to 10g per day are well tolerated without notable side effects.
How much citrulline should I take per day?
Take 6-8g L-citrulline or 8-10g citrulline malate about 30-40 minutes before training. Many pre-workouts only contain 3g, which is really too little for a noticeable effect.
Scientific sources
The clinical dosages on this page are based on peer-reviewed research.
- Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-AnalysisVårvik FT et al. (2021)
- Effects of Citrulline Supplementation on Different Aerobic Exercise Performance Outcomes: A Systematic Review and Meta-AnalysisViribay A et al. (2022)
- l-Citrulline Supplementation: Impact on Cardiometabolic HealthAllerton TD et al. (2018)Funded by: Beurzen van de Amerikaanse NIH (NCCIH). De auteurs melden geen belangenverstrengeling.
- Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysisHarnden CS et al. (2023)
Pre-workouts with Citrulline
Cellucor C4 Ultimate
Premium C4 with 300mg caffeine, 6g citrulline malate, 3.2g beta-alanine, and 3g creatine. Fully clinically dosed — top of the C4 line.
BSN N.O.-Xplode
3 flavors
Legendary pre-workout from BSN with 6g citrulline, 3g creatine, and 200mg caffeine. Popular for years with a complete formula for energy and pump.
5% Nutrition 5150
2 flavors
Hardcore pre-workout with 400mg caffeine from multiple sources, 4g citrulline, and 2.5g beta-alanine. Not for beginners — one of the strongest pre-workouts on the market.
JNX Sports Shadow-X
Thermogenic pre-workout from JNX Sports with 200mg caffeine, 2g citrulline, and 2g beta-alanine. Focus on energy and concentration.
Cellucor C4 Ripped
2 flavors
C4 variant for the cutting phase with L-Carnitine and CLA. Less caffeine (150mg), no creatine — focused on fat burning.
We keep the dosages and values on this page as accurate as possible based on selected studies. New research may change these values. Nothing on this page is medical advice. If you have any doubts, always consult a doctor.