Benefits
Repetitions during strength training
In pooled data from 8 placebo-controlled studies in 137 people, 6 to 8 g of citrulline malate taken 40 to 60 minutes before lifting added about 3 repetitions (6.4%) before failure, a small effect. A pooled analysis of 4 trials in resistance-trained adults found no clear gain in muscle strength, and single trials, including one testing it against plain L-citrulline, found no extra repetitions.
Overall exercise performance
Pooled data from 30 randomized trials in 644 people found a small overall improvement in exercise performance, with wide prediction intervals and no change in perceived effort; the authors rated certainty low to very low. Signs of benefit for endurance and short sprints did not hold up in sensitivity checks, and a cycling trial of 12 g found no change in sprint power or time to exhaustion.
Muscle soreness after exercise
Pooled data from 13 trials of L-citrulline or citrulline malate in 206 healthy people, most often 8 g of citrulline malate, found less muscle soreness 24 hours after exercise, but not at 48 or 72 hours. Single trials disagree: one reported 40% less soreness, another more soreness than placebo. The EU food safety authority found that a link to faster recovery from muscle fatigue was not established.
Blood arginine and blood vessel widening
In 12 healthy young men, 6 g and 12 g of citrulline malate raised blood citrulline, arginine and ornithine within 2 hours, more with the larger dose, but did not change flow-mediated dilation, a measure of how well an artery widens. In another trial in 24 young adults, 8 g increased flow-mediated dilation 60 minutes later compared with placebo.
Blood pressure after a treadmill session
In a randomized trial in 20 adults with high blood pressure, a single 6 g dose taken 2 hours before 40 minutes of treadmill walking or running lowered diastolic blood pressure over the next 24 hours more than placebo (14 versus 6 mmHg). Systolic pressure and the usual nighttime dip in blood pressure did not differ between groups.
Mechanism of action
Citrulline to arginine and nitric oxide
Citrulline is converted in the body to arginine, the substrate nitric oxide synthase uses to make nitric oxide, which relaxes blood vessels. A review notes that studies show oral L-citrulline to be the most efficient way to raise blood arginine. In healthy young men, 6 g and 12 g of citrulline malate raised blood arginine and the arginine to ADMA ratio, a marker favoring nitric oxide production, within 2 hours.
Malate and muscle energy
Malate is an intermediate of the tricarboxylic acid (Krebs) cycle, which muscle cells use to make ATP. In a before-and-after study in 18 men with fatigue but no documented disease, 6 g a day of citrulline malate for 15 days was followed by a 34% faster rate of oxidative ATP production in a forearm muscle and less reported fatigue. A later trial found that neither citrulline alone nor citrulline with malate improved strength or repetitions.
Ammonia and the urea cycle (proposed)
Citrulline is part of the urea cycle, the route the body uses to clear ammonia, and ammonia production rises during high-intensity exercise. Reviewers propose that better ammonia handling could delay fatigue, but in the trials cited here citrulline did not change blood lactate, and citrulline malate did not change acid and base balance during sprints.
Clinical trials
Randomized, double-blind, 2-period crossover trial: 8 g of citrulline malate or placebo before a chest training session, with repetitions to fatigue at 80% of one-repetition maximum tested in 8 bench press sets (Pérez-Guisado et al. 2010, J Strength Cond Res)
41 men.
Repetitions rose with citrulline malate from the third tested set onward (p < 0.0001), reaching 52.92% more in the last set. Muscle soreness was 40% lower at 24 and 48 hours. Stomach discomfort in 14.63% of the men was the only side effect reported.
Randomized, double-blind, placebo-controlled, counterbalanced trial on an isokinetic chair (attempted 10 sets of 10 repetitions at 70% of peak concentric force); lab analysis showed the citrulline malate used had a 1.11:1 ratio (4.21 g of citrulline per 8 g), and the authors warn that product analyses differed from manufacturers' claims (Chappell et al. 2018, J Int Soc Sports Nutr)
15 recreationally active men and women.
Repetitions did not differ (94.0 on placebo versus 90.9 on citrulline malate, P = 0.33), and neither did isometric, concentric or eccentric peak force. Total muscle soreness over 72 hours was higher with citrulline malate than placebo (P = 0.01).
Randomized, double-blind, placebo-controlled crossover trial (NCT05183893): placebo, 5.3 g of L-citrulline, or citrulline malate supplying 5.3 g of citrulline plus 2.7 g of malate, 45 minutes before testing (Martín-Olmedo et al. 2025, Int J Sport Nutr Exerc Metab)
43 young, trained adults (21 women).
Neither form improved maximal or ballistic strength, total repetitions in squat and bench press, lifting velocity, or perceived exertion compared with placebo (all p values 0.061 or higher).
Double-blind, placebo-controlled crossover trial: 12 g of citrulline malate or placebo 60 minutes before 10 maximal 15-second sprints and a time-to-exhaustion test (Cunniffe et al. 2016, J Strength Cond Res)
10 well-trained men.
Plasma citrulline rose 8.8-fold, but time to exhaustion (120 versus 113 seconds), peak and mean power, perceived exertion and acid and base markers did not differ from placebo; exercise heart rate was higher. No gastrointestinal side effects occurred during testing.
Systematic review and meta-analysis of double-blind, placebo-controlled studies of citrulline malate and repetitions to failure in upper and lower body exercises (Vårvik et al. 2021, Int J Sport Nutr Exerc Metab)
137 participants in 8 studies: 101 strength-trained men, 26 strength-trained women and 9 untrained men.
6 to 8 g taken 40 to 60 minutes before exercise added 3 repetitions (6.4%) versus placebo (p = .022), a small standardized effect of 0.196. Lower body showed a tendency (p = .051) and upper body no significant effect (p = .131).
Systematic review and meta-analysis of randomized controlled trials in resistance-trained adults, registered in PROSPERO (Aguiar et al. 2022, J Diet Suppl)
Resistance-trained adults in 4 trials (69 citrulline malate and 69 placebo assessments).
No overall effect on muscle strength (SMD 0.13, 95% CI -0.21 to 0.46), with no clear effect for lower or upper limbs.
Systematic review and three-level meta-analysis of randomized controlled trials searched to August 2025, with GRADE certainty ratings; no external funding (Wang et al. 2026, Nutrients)
644 participants in 30 randomized trials (138 effect sizes).
Small improvement in overall exercise performance (g = 0.16, p = 0.01) with wide prediction intervals and limited power; no significant effect on perceived exertion. Endurance and short anaerobic subgroups were not robust in sensitivity analyses. Certainty was rated low to very low.
Systematic review and meta-analysis of randomized controlled trials of L-citrulline or citrulline malate taken within 2 hours before exercise; 8 g of citrulline malate was the most frequent dose (Rhim et al. 2020, J Sport Health Sci)
206 healthy participants in 13 trials.
Lower perceived exertion (p = 0.03) and muscle soreness 24 hours after exercise (p = 0.04); soreness at 48 hours (p = 0.25) and 72 hours (p = 0.62) and blood lactate (p = 0.17) did not differ.
Randomized, double-blind, placebo-controlled crossover trial with measurements 60 and 120 minutes after intake; one author is Chief Scientific Officer of a supplement company, SHIFTED LLC, and the authors report no financial support (Grannes et al. 2026, Front Physiol)
12 healthy, recreationally active young men; blood markers in a subgroup of 6.
Flow-mediated dilation did not change with either dose (interaction p = 0.315). Both doses raised peak serum citrulline, arginine and ornithine and the arginine to ADMA and SDMA ratios (all p < 0.001), more with 12 g.
Randomized, double-blind, placebo-controlled crossover trial of 8 g of citrulline malate, 1.5 g of Nitrosigine or 8 g of dextrose placebo, measured 60 minutes after intake; funded by state and university undergraduate research grants, with publication costs paid by an unrestricted grant from Nutrition 21, LLC, the supplier of Nitrosigine, which had no other involvement (Rogers et al. 2020, J Int Soc Sports Nutr)
24 healthy, normotensive young adults (16 men, 8 women).
Flow-mediated dilation rose 34% after citrulline malate versus a 2% fall after placebo (supplement by time effect p < .001).
Randomized, double-blind, placebo-controlled parallel trial (NCT03378596): 6 g of citrulline malate or 6 g of corn starch 120 minutes before 40 minutes of treadmill walking or running, then 24-hour ambulatory monitoring (Domingues et al. 2024, J Diet Suppl)
20 adults with high blood pressure, mean age 55.
Diastolic blood pressure fell more over 24 hours (-14 versus -6 mmHg, p = 0.047) and while awake (-12 versus -4 mmHg, p = 0.024). Systolic pressure and the nighttime dip did not differ between groups.