L-Citrulline Dosage: How Much to Take Per Day, When to Take It and Safety

Short answer: Most human studies use an L-citrulline dosage of about 1.5 to 3 grams per day for circulation goals, often split into two or three doses, and about 6 to 8 grams of citrulline malate taken roughly an hour before exercise for workout goals. Citrulline malate is weaker per gram, so you need about 1.76 g of it to get 1 g of citrulline. No official optimal dose has been set for any condition, and anyone who takes nitrates, erectile dysfunction drugs or blood pressure medicine should talk to a doctor first.

Key Takeaways

• Circulation goals: 1.5 to 3 g of L-citrulline per day is the range used in most human research, commonly split across the day.^[1][2]
• Exercise goals: studies on lifting and fatigue usually use 6 to 8 g of citrulline malate about 60 minutes before training.^[1]
• Form matters: L-citrulline is pure citrulline; citrulline malate is bound to malic acid, so read the label and convert.^[1]
• Well tolerated: single doses up to 15 g caused no side effects in a small dose-ranging study in healthy men; upset stomach is the most commonly reported issue.^[3][4]
• Real interaction risk: do not combine it with nitrates or PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) without medical advice, because blood pressure can drop too far.^[5]

What Is L-Citrulline?

L-citrulline is an amino acid your body makes on its own and also gets from food, with watermelon being the best known source.^[5] It is not one of the amino acids used to build proteins. Its main job is as an intermediate in the urea cycle and in the recycling loop that feeds nitric oxide production.

The reason people supplement it is simple: the kidneys convert citrulline into L-arginine, and arginine is the raw material the body uses to make nitric oxide, a gas that signals blood vessel walls to relax.^[4] Oral citrulline reliably raises blood levels of both citrulline and arginine, as well as markers of nitric oxide (nitrate and nitrite).^[6]

If you are wondering why people take citrulline to raise arginine instead of just taking arginine, that comparison has its own guide: L-arginine vs L-citrulline for blood flow. One practical difference worth knowing here: large doses of arginine (10 g or more) can cause diarrhea, while citrulline has not shown that problem at similar amounts.^[1]

L-Citrulline Dosage by Goal

There is no government recommended intake for citrulline, and WebMD notes that optimal doses have not been set for any condition.^[5] What we do have is a consistent pattern in the doses researchers actually used. The table below pulls those numbers together.

How much L-citrulline per day for circulation?

Examine.com, which summarizes the human trials, suggests 1,000 mg three times a day (3 g total) for circulatory health, and notes it does not have to be taken with meals.^[1] Many people start at the lower end, around 1.5 g per day, which is the amount used in the best known erection study, and move up only if they tolerate it well.

How much citrulline malate before a workout?

For training, the dose is higher and is taken once, before the session. Examine lists 6 to 8 g of citrulline malate about an hour before exercise.^[1] In one weightlifting trial cited there, 8 g of citrulline malate increased the number of repetitions on later sets compared with placebo.^[1] Results for endurance and aerobic exercise are much weaker, and WebMD reports that research does not show a performance gain in well trained athletes.^[5]

Converting citrulline malate to L-citrulline

Citrulline malate products are common, but part of each gram is malic acid. Using the 1.76 to 1 ratio from Examine, 3 g of L-citrulline equals roughly 5.3 g of citrulline malate.^[1] Labels vary (some products use a 2 to 1 blend), so check how many grams of actual citrulline the serving provides before comparing products.

What the Evidence Shows

Human studies

• Blood levels: in a dose-ranging study, 8 healthy men took single oral doses of 2, 5, 10 and 15 g. Plasma arginine peaked roughly 1 to 2.3 hours after the dose, less than 5% of the citrulline was lost in urine, and arginine rose less than expected at the highest doses, suggesting the body’s conversion capacity starts to saturate.^[3] In practical terms, mega doses add little.
• Blood pressure: Examine rates the effect as minor and notes it may only appear in people with elevated or high blood pressure. One cited trial used a watermelon extract providing 1,350 mg citrulline plus 650 mg arginine twice daily for 6 weeks in prehypertensive adults.^[1] WebMD adds that the small reductions seen may not be clinically meaningful.^[4]
• Exercise: a 2020 review in the Journal of Strength and Conditioning Research found that several studies report better performance and recovery, but that direct evidence for improved blood flow to muscle during exercise is scarce and inconsistent.^[6]
• Erection hardness: in a small single-blind study of 24 men (average age about 56) with mild symptoms, 1.5 g per day for one month moved 12 of 24 men (50%) up to a normal hardness score, compared with 2 of 24 (8.3%) on placebo, with no reported adverse events.^[2] This was one small, short study, and both Examine and WebMD note citrulline is not as potent as prescription medication.^[1][5]

Animal studies

Animal research suggests possible roles in wound healing, muscle protein in older animals and gut health, and rats tolerated very large doses.^[1][5] These findings are interesting for researchers, but they do not tell you what dose a human should take.

Timing: Daily Use vs Before an Event

Because blood arginine peaks about one to two hours after a dose,^[3] timing depends on what you want:

• Daily routine: for steady circulation support, split the daily amount (for example 1.5 g twice a day or 1 g three times a day). Most human data on blood pressure and erection hardness come from several weeks of daily use, not single doses.^[1][2]
• Before training: take citrulline malate about 60 minutes before the session.^[1]
• With food or not: either works. If your stomach is sensitive, taking it with a meal and splitting the dose usually helps.

Consistency matters more than chasing a higher number. The Citrudose data show that conversion to arginine flattens out at high single doses, so going beyond the studied ranges is unlikely to add benefit.^[3]

Side Effects and Safety

L-citrulline has a good tolerance record in the studies above. The dose-ranging trial reported no side effects at any dose up to 15 g, and Examine notes that, unlike arginine and ornithine at 10 g or more, citrulline did not cause diarrhea or intestinal upset at that amount.^[1][3] WebMD lists upset stomach as the most common side effect and, rarely, allergic reactions (hives, swelling, trouble breathing) that require stopping the product and getting help right away.^[4]

Two practical warnings deserve attention:

• Label accuracy: some “nitric oxide booster” products mix citrulline with other ingredients, including caffeine that may not be clearly listed, and the FDA does not verify supplement labels.^[4] Choosing third-party tested supplements reduces that risk.
• Long term data are limited: most trials run from a single day to a few weeks, so long term safety at high doses is less well documented.

Who Should Talk to a Doctor First

Because citrulline works through nitric oxide and blood vessel relaxation, it can add to the effect of drugs that do the same thing. Speak with a clinician before using it if any of these apply:^[4][5]

• You take nitrates for chest pain (nitroglycerin, isosorbide dinitrate or mononitrate).
• You take a PDE-5 inhibitor such as sildenafil, tadalafil, vardenafil or avanafil. WebMD warns the combination may cause a dangerous drop in blood pressure.
• You take any blood pressure medicine, or your blood pressure runs low.
• You have heart disease, a past heart attack, peripheral vascular disease, or kidney or liver problems.
• You are pregnant or breastfeeding (safety is not established).

A note on erections: changes in erection quality can be linked to blood vessel health, hormones, sleep, stress or medications. That is a reason to see a doctor first rather than self-experimenting with supplements, because a clinician can look for the underlying cause.

Where Ultra Bann Fits

To be clear about the product on this site: citrulline is not an ingredient. Ultra Bann is a botanical formula by DL Bioproducts with seven plant extracts per serving and every amount on the label, no proprietary blend: Thai Butea superba 345 mg, Panax ginseng 110 mg, Cynomorium songaricum 85 mg, black ginger (Kaempferia parviflora) 85 mg, tongkat ali 85 mg, epimedium (horny goat weed) 45 mg and reishi 45 mg, for 800 mg total. You take one capsule every 2 days. You can review the full label on the Ultra Bann ingredients page and read more about one of those herbs in our guide to Panax ginseng for men.

If you already use an amino acid product, show both labels to your doctor or pharmacist before combining them. First orders of Ultra Bann include free US shipping and a 60-day money-back guarantee, available in the Ultra Bann shop.

Frequently Asked Questions

How much L-citrulline should I take per day?

Most human research uses 1.5 to 3 g of L-citrulline per day for circulation related goals, often split into two or three doses. For workouts, studies typically use 6 to 8 g of citrulline malate about an hour before training. No official optimal dose exists, so start low and ask your doctor if you take any medication.

Is 6 grams of L-citrulline too much?

For healthy adults, 6 g per day has been used in short term studies of up to about 16 days, and single doses up to 15 g caused no side effects in a small dose-ranging study. Higher doses add little, because conversion to arginine starts to level off. People on nitrates, PDE-5 inhibitors or blood pressure medicine should not use any dose without medical advice.

How long does L-citrulline take to work?

Blood arginine levels peak roughly 1 to 2.3 hours after a dose, which is why pre-workout use is timed about an hour before training. Effects on blood pressure and erection hardness in studies were measured after weeks of daily use (for example one month at 1.5 g per day), not after a single dose.

Is it better to take L-citrulline or citrulline malate?

Both raise blood citrulline and arginine. L-citrulline gives you more citrulline per gram, while citrulline malate is the form used in most strength training studies. If you switch forms, multiply your L-citrulline dose by about 1.76 to get the equivalent amount of citrulline malate.

Can I take L-citrulline every day?

Daily use at 1.5 to 3 g is the pattern used in most circulation studies, and tolerance has been good in those trials. Long term data are limited, so periodic check-ins with your doctor make sense, especially if you have heart, kidney or blood pressure concerns.

References

1. Examine.com. Citrulline: research summary, dosage and side effects.
2. Cormio L, De Siati M, Lorusso F, Selvaggio O, Mirabella L, Sanguedolce F, Carrieri G. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. 2011;77(1):119 to 122.
3. Moinard C, Nicolis I, Neveux N, Darquy S, Bénazeth S, Cynober L. Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the Citrudose pharmacokinetic study. British Journal of Nutrition. 2008;99(4):855 to 862.
4. WebMD. L-Citrulline: uses, side effects, warnings and interactions.
5. WebMD. L-citrulline: uses and risks.
6. Gonzalez AM, Trexler ET. Effects of citrulline supplementation on exercise performance in humans: a review of the current literature. Journal of Strength and Conditioning Research. 2020;34(5):1480 to 1495.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. This article is for information only and is not medical advice.