L-Citrulline Supplements: What It Is, If It Works & What to Buy
L-citrulline is an amino acid your body turns into arginine, which it uses to make nitric oxide, a gas that relaxes blood vessels. The research finds small effects: about 4 points off the top blood pressure number in one review (another found none), and about 3 more reps before lifting. Our pick: Nutricost Pure L-Citrulline, $0.33 for 6 g.
By Erin Rose Updated October 19, 2026 How we score
Costs are brand prices for 6 g of actual citrulline (October 19, 2026).
What to buy
Nutricost Pure L-Citrulline is our pick. It is pure citrulline, 3 g a scoop, so 2 scoops give the 6 g studies often used.
Nutricost Pure L-Citrulline
Pure · $0.33 for 6 g
Get drug-tested for sport? Kaged L-Citrulline is on Informed Sport, a list that tests for substances banned in sport.
Kaged L-Citrulline
Informed Sport · $0.60 for 6 g
Where to go next
- Best L-citrulline: the products we compared, ranked.
- L-citrulline dosage guide: how much to take, including over 60.
- L-citrulline prices: what 6 g costs for each product.
- L-citrulline vs L-arginine: which to take.
What L-citrulline does
Your kidneys turn citrulline into arginine. Taking citrulline raised blood arginine more than taking arginine itself (Schwedhelm 2008), which is why it is sold for blood flow.
| Goal | Effect | What trials found |
|---|---|---|
| Blood pressure | Small | The top number fell about 4 points in a review of 8 trials; the bottom number did not fall by a clear amount. Another review found no effect. |
| Workouts | Small | 6 to 8 g of citrulline malate before lifting gave about 3 more reps in a review. |
| Erections | One small trial | In one small trial that was not randomized, 1.5 g a day helped 12 of 24 men with mild problems, against 2 of 24 on placebo (Cormio 2011). |
| Adults over 60 | Small, mixed | Small blood pressure drops, and faster walking only when taken with exercise. More. |
| Muscle protein in older men | One small trial, no effect | After one meal, citrulline did not raise muscle protein building in 21 men aged 65 to 80. |
Citrulline malate is not all citrulline
Most pre-workouts use citrulline malate, citrulline mixed with malic acid. At best about 72% of it is citrulline, so a “6,000 mg” scoop holds about 4.3 g. A lab test of five 2:1 powders found some held less (Chappell 2018). Pure L-citrulline avoids the question. How to work out your scoop.
How much to take
3 to 6 g of pure L-citrulline a day, 2 scoops of our pick. The dosage guide has doses by goal and a calculator.
Is L-citrulline safe?
WebMD lists no known side effects. In trials the most common was an upset stomach: about 1 in 7 men had it after 8 g of citrulline malate (Pérez-Guisado 2010). Healthy men took up to 24 g a day for 4 weeks with no harm found (Miura 2023). A few things to check:
- Nitrates for the heart or ED drugs (for erections) like sildenafil: don’t take citrulline unless your doctor says yes. Blood pressure may drop too far (WebMD).
- Blood pressure medicine: ask your doctor first.
- Pregnant or breastfeeding: WebMD says not to take it.
Questions people ask
Is L-citrulline better than L-arginine?
For raising blood arginine, yes: in a trial of 20 adults, citrulline raised it more than arginine itself did (Schwedhelm 2008). Neither improved blood vessel function in that trial. L-citrulline vs L-arginine.
Can I get it from watermelon?
Some. Watermelon flesh averaged about 2 mg of citrulline per gram, and red melons held less than yellow or orange ones (Rimando 2005). By our math, the 6 g many studies used would take 3 kg of melon or more.
Sources
- Schwedhelm E, et al. “Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism.” Br J Clin Pharmacol. 2008. PubMed 17662090
- Barkhidarian B, et al. “Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis.” Avicenna J Phytomed. 2019. PubMed 30788274
- Mirenayat MS, et al. “Effect of L-Citrulline Supplementation on Blood Pressure: a Systematic Review and Meta-Analysis of Clinical Trials.” Curr Hypertens Rep. 2018. PubMed 30284051
- Vårvik FT, et al. “Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis.” Int J Sport Nutr Exerc Metab. 2021. PubMed 34010809
- Cormio L, et al. “Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction.” Urology. 2011. PubMed 21195829
- Churchward-Venne TA, et al. “Citrulline does not enhance blood flow, microvascular circulation, or myofibrillar protein synthesis in elderly men at rest or following exercise.” Am J Physiol Endocrinol Metab. 2014. PubMed 24824653
- Chappell AJ, et al. “Citrulline malate supplementation does not improve German Volume Training performance or reduce muscle soreness in moderately trained males and females.” J Int Soc Sports Nutr. 2018. PubMed 30097067
- Pérez-Guisado J, Jakeman PM. “Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness.” J Strength Cond Res. 2010. PubMed 20386132
- Miura N, et al. “Subchronic tolerance trials of graded oral supplementation with ornithine hydrochloride or citrulline in healthy adults.” Amino Acids. 2023. PubMed 36571619
- Rimando AM, Perkins-Veazie PM. “Determination of citrulline in watermelon rind.” J Chromatogr A. 2005. PubMed 16007998
- WebMD. “L-citrulline.” Medically reviewed August 14, 2025. webmd.com