L-citrulline: effects and dosage? Is it more effective than L-Arginine?

Q: Why is L-citrulline better than L-arginine?

A large part of orally taken L-arginine is broken down in the digestive tract and the liver. Citrulline prevents this breakdown by blocking the enzyme arginase and moreover does not cause gastrointestinal problems even at higher doses of 6 g.

Q: How should you dose L-citrulline?

The most optimal approach is chronic dosing of 6 g of citrulline a day for at least 6 days, with the last dose taken 1–2 hours before physical activity. A single acute dose usually does not lead to an immediate improvement in performance.

Q: What does L-citrulline help with?

L-citrulline demonstrably reduces the level of ammonia (which is linked to fatigue), improves endurance and performance at high intensity. It is considered one of the few supplements with scientifically supported ergogenic potential.

March 11, 2026Michal Jetelina0 comments

Mechanism of action: the arginine cycle

The main importance of citrulline lies in its role in the metabolism of amino acids:

Arginine synthesis – citrulline is used for the synthesis of arginine and accounts for up to 60 % of the de novo synthesis of arginine in the body.

Production of nitric oxide (NO) – arginine is converted by the enzyme nitric oxide synthase (NOS) into nitric oxide and citrulline.

Nitric oxide (NO) acts as a strong vasodilator – it widens the blood vessels, improves blood flow and the delivery of oxygen and nutrients to the working muscles and reduces the amount of ATP needed for muscle force. The result is better endurance and recovery (Bescós et al., 2012).

Why choose L-citrulline instead of L-arginine?

L-citrulline is a much more effective provider of nitric oxide than L-arginine itself, for two reasons:

Advantage of citrulline

No digestive problems

Unlike arginine, L-citrulline causes neither nausea nor cramps even at higher doses of 6 g.

Advantage of citrulline

Better bioavailability

A large part of L-arginine is broken down by the enzyme arginase in the liver. Citrulline blocks the activity of arginase and so prevents this breakdown. Taking it for 7 days increases the concentration of arginine in the plasma and NO production (Schwedhelm et al., 2008).

Effects on sports performance and recovery

Research on citrulline supplementation shows three key benefits:

Reduced ammonia

It suppresses exercise-induced hyperammonaemia – ammonia is linked to fatigue (Aguayo et al., 2021)

Better endurance

6 g a day for 7 days → a slight improvement in time trial performance and reduced perceived exertion in cyclists (Stanelle et al., 2020)

High-intensity performance

An improvement in high-intensity performance after 7 days of taking 6 g/day (Bailey et al., 2015)

Dosage and timing

The difference between acute and chronic use is fundamental (Viribay et al., 2022):

Works

Chronic use

Dose3.4–6 g / day

Duration6–16 days

Last dose1–2 h before exercise

Does not work

Acute use

Single dose1–12 g

Timing1–3 h before exercise

Resultno effect

Recommendation: A loading protocol of 6 g of citrulline a day for at least 6 days, with the last dose 1–2 hours before exercise. A pre-workout combining caffeine and L-citrulline is also a suitable choice.

Conclusion for athletes

L-citrulline is currently considered one of the few supplements with scientifically supported ergogenic potential – it raises the level of arginine and NO production without side effects on digestion. We definitely recommend adding it to your supplement routine to improve physical performance.

References

Bescós R, Sureda A, Tur JA, Pons A. (2012). The effect of nitric-oxide-related supplements on human performance. Sports Med, 42:99–117.
Schwedhelm E, Maas R, Freese R, et al. (2008). Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: Impact on nitric oxide metabolism. Br J Clin Pharmacol, 65:51–59.
Aguayo E, Martínez-Sánchez A, Fernández-Lobato B, Alacid F. (2021). L-citrulline: A non-essential amino acid with important roles in human health. Appl Sci, 11:3293.
Stanelle ST, McLaughlin KL, Crouse SF. (2020). One week of L-citrulline supplementation improves performance in trained cyclists. J Strength Cond Res, 34(3):647–652.
Bailey SJ, Blackwell JR, Lord T, et al. (2015). L-citrulline supplementation improves O₂ uptake kinetics and high-intensity exercise performance in humans. J Appl Physiol, 119(4):385–395.
Viribay A, Fernández-Landa J, Castañeda-Babarro A, et al. (2022). Effects of citrulline supplementation on different aerobic exercise performance outcomes: A systematic review and meta-analysis. Nutrients, 14(17):3479.
Jeukendrup A, Gleeson M. (2025). Sport nutrition (4th ed.). Human Kinetics.

L-citrulline: effects and dosage? Is it more effective than L-Arginine?

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