L-Citrulline
Also known as Citrulline malate, Citrulline
L-Citrulline is a non-essential amino acid that the body converts to arginine far more efficiently than supplemental arginine itself, bypassing the gut and liver breakdown that limits oral arginine absorption. This makes it the preferred way to raise blood arginine and nitric oxide levels, giving better pumps, improved endurance, and reduced muscle soreness. Citrulline malate (paired with malic acid) is the most studied form for exercise performance.
Benefits
Raises nitric oxide more effectively than arginine
StrongCitrulline survives gut and liver metabolism intact, reaching the kidneys where it is converted to arginine. Blood arginine levels rise higher with citrulline than with the same dose of arginine.
Improves exercise endurance and reduces fatigue
ModerateCitrulline malate at 6–8 g pre-workout increases reps to failure, delays fatigue, and reduces perceived exertion in both resistance and endurance training.
Reduces post-exercise muscle soreness
ModerateMultiple trials show significantly lower DOMS scores 24–48 hours after training with citrulline malate supplementation.
Supports blood pressure and vascular health
ModerateBy raising nitric oxide, citrulline dilates blood vessels and has shown modest reductions in blood pressure in several trials.
Pros & cons
Pros
- Better absorbed and more effective than arginine for raising NO
- Well tolerated with minimal side effects
- Strong pre-workout evidence at 6–8 g citrulline malate
- No herpes-flare risk unlike arginine
Cons
- Needs a fairly large dose (6–8 g) for performance benefit
- Citrulline malate vs pure citrulline dosing can be confusing (malate form is ~57% citrulline by weight)
Side effects
GI discomfort at high doses
Generally very well tolerated; occasional bloating at doses above 10 g.
Blood pressure drop
May lower blood pressure meaningfully; caution alongside antihypertensives.
How to take it
Typical dose
6–8 g citrulline malate (2:1) or 3–4 g pure L-Citrulline, 30–60 min pre-workout
Timing
30–60 minutes before exercise
Common forms
Tip: Citrulline malate 2:1 means 2 parts citrulline to 1 part malic acid. 8 g of citrulline malate ≈ 5.6 g pure citrulline.
What the research says
[1]Citrulline malate and resistance exercise
PreliminaryTrials are mixed: some report more repetitions and less soreness with 8 g before training, while a controlled study found no improvement in muscle recovery.
RCTs · 2017PubMed[2]Citrulline vs arginine for blood arginine levels
StrongOral citrulline raises plasma arginine levels more effectively than equimolar arginine due to better intestinal absorption and reduced splanchnic extraction.
Pharmacokinetic studies · 2015PubMed
How L-Citrulline interacts
Synergies, absorption effects, and cautions between L-Citrulline and other supplements in the matrix.
L-Citrulline and its direct connections · click a node to open its guide
Citrulline is converted to arginine in the kidneys; it is the superior oral strategy for raising arginine and nitric oxide levels.
Compare the pairingA popular pre-workout pairing: citrulline for blood flow and pumps, creatine for power and strength output.
Compare the pairingVitamin C protects nitric oxide from oxidative degradation, extending the vasodilatory effect of citrulline-derived NO.
Compare the pairingFrequently asked questions
What is L-Citrulline used for?
L-Citrulline is most commonly used for energy, recovery, and heart health. Citrulline survives gut and liver metabolism intact, reaching the kidneys where it is converted to arginine. Blood arginine levels rise higher with citrulline than with the same dose of arginine.
How much L-Citrulline should I take?
A typical dose is 6–8 g citrulline malate (2:1) or 3–4 g pure L-Citrulline, 30–60 min pre-workout. Citrulline malate 2:1 means 2 parts citrulline to 1 part malic acid. 8 g of citrulline malate ≈ 5.6 g pure citrulline. Start at the lower end and confirm the right dose for you with a healthcare professional.
When is the best time to take L-Citrulline?
Recommended timing: 30–60 minutes before exercise.
What are the side effects of L-Citrulline?
Reported side effects include gi discomfort at high doses and blood pressure drop. Generally very well tolerated; occasional bloating at doses above 10 g.
Who should be careful with L-Citrulline?
Caution with antihypertensive medications or PDE5 inhibitors (Viagra, Cialis). Speak with a healthcare professional if any of these apply to you.
Important cautions
- Caution with antihypertensive medications or PDE5 inhibitors (Viagra, Cialis).
- Unlike arginine, citrulline does not promote herpes simplex replication.
More Amino Acids
5-HTP
A direct serotonin precursor for mood and sleep, use with care.
Collagen
The structural protein for skin, joints, and connective tissue.
Creatine
The most-studied performance and cognition supplement.
Compare L-Citrulline with
Weighing your options? See how L-Citrulline stacks up against similar supplements.
Supports these foundations
L-Citrulline can help reinforce these lifestyle foundations, but it works best on top of them, not in place of them.