Citrulline also raised two urine markers of nitric oxide. But neither citrulline nor arginine improved how well blood vessels widen in that trial.
Ready to buy:
Nutricost Pure L-Citrulline
$0.33 for 6 g (2 scoops) at the brand’s price, checked October 19, 2026. Why it is our pick.
Who should pick which
We pick citrulline because it raises blood arginine more, and arginine carries a heart-attack warning. These are the cases where the choice changes.
Get drug-tested for sport? Get a tested citrulline.
Kaged L-Citrulline is on Informed Sport, a list that tests for substances banned in sport. It costs more than our pick for the same citrulline.
Kaged L-Citrulline
Informed Sport · $0.60 for 6 g
Had a heart attack? Don’t take arginine.
In a trial after heart attacks, 6 of the people taking arginine died and none on placebo did, and the trial was stopped (Schulman 2006). Ask your heart doctor before taking either one.
Your doctor named arginine? Take what they said.
This page compares the two as supplements you choose yourself. If a doctor chose arginine for you, ask before you switch.
Take nitrates or ED drugs? Don’t, unless your doctor says yes.
WebMD says not to take citrulline with nitrates for the heart or ED drugs (for erections) like sildenafil, because blood pressure may drop too far. It also says not to use citrulline if you are pregnant or breastfeeding.
Why citrulline raises arginine more
Much of the arginine you swallow is used up by your gut and liver before it reaches your blood (Bahadoran 2021). Citrulline gets past them. Your kidneys then turn it into arginine. In a one-week trial of 20 adults, citrulline raised blood arginine more than arginine did, and more citrulline raised it more (Schwedhelm 2008).
What that does for blood pressure
For citrulline, the effect is small. The top blood pressure number fell about 4 points in a review of 8 trials (Barkhidarian 2019), and another review found no effect (Mirenayat 2018). Arginine has its own review: across 11 trials, 4 to 24 g a day lowered the top number about 5 points, also a small effect (Dong 2011). No trial has compared the two head to head for blood pressure. In middle-aged and older adults, trials that combined them gave the biggest drops (Luo 2025). Neither is a treatment for high blood pressure.
Frequently asked questions
Can I take L-citrulline and L-arginine together?
Yes, many products mix them. In a review of trials in middle-aged and older adults, the biggest blood pressure drops came from trials that combined the two (Luo 2025). Do not take arginine if you have had a heart attack (Schulman 2006). Ask your doctor first if you take blood pressure, nitrate or ED medicine.
Why is L-citrulline better than L-arginine?
Because it gets more arginine into your blood. Swallowed arginine is largely broken down before it gets there; citrulline is not. See why.
How much L-citrulline should I take?
Many studies used 3 to 6 g a day. The 2008 trial used up to 3 g twice a day. Dosage guide.
Related guides
- L-citrulline dosage guide: how much to take
- Best L-citrulline: our full ranking
- L-citrulline guide: what it is and what the research found
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. PMID: 17662090
- Bahadoran Z, et al. “Endogenous flux of nitric oxide: Citrulline is preferred to Arginine.” Acta Physiol (Oxf). 2021. PMID: 33089645
- Barkhidarian B, et al. “Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis.” Avicenna J Phytomed. 2019. PMID: 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. PMID: 30284051
- Luo P, et al. “Does l-citrulline supplementation and watermelon intake reduce blood pressure in middle-aged and older adults? A systematic review and meta-analysis of randomized controlled trials.” Clin Nutr ESPEN. 2025. PMID: 40789388
- Dong JY, et al. “Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trials.” Am Heart J. 2011. PMID: 22137067
- Schulman SP, et al. “L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial.” JAMA. 2006. PMID: 16391217
- WebMD. “L-citrulline.” Medically reviewed August 14, 2025. webmd.com