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L-Arginine vs L-Citrulline
Compare L-Arginine and L-Citrulline: timing, food, doses, forms and existing interaction guidance.
| L-Arginine | L-Citrulline | |
|---|---|---|
| Category | Amino acids | Amino acids |
| Best time | Breakfast / Lunch / Dinner | On waking / Breakfast / Lunch |
| Food | With or without food | With or without food |
| Common dose | 3000–9000 mg | 3000–6000 mg |
| Upper limit | Not established | Not established |
| Solubility | Water-soluble | Water-soluble |
| Description | Amino acid the body uses to make nitric oxide. In a meta-analysis, 4–24 g/day lowered blood pressure by about 5/3 mmHg. In a trial after heart attacks, more people died on arginine than on placebo, so it should not be used after a heart attack. | Amino acid (named after watermelon) that the kidneys turn into arginine. It raises blood arginine more effectively than arginine itself, and in a meta-analysis it lowered blood pressure by about 4/3 mmHg in middle-aged and older adults. |
| Timing note | Split into two or three doses; large single doses can upset the stomach. | For exercise, usually taken before a workout; otherwise split into two daily doses. |
| Forms to look for |
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| References |
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Common product or study range — not a personal recommendation. Upper limits are ceilings, not targets.
If you take both
Yes — combining them lowered blood pressure more than citrulline alone in trials.
Fine to combine. If you take blood-pressure medication, watch for dizziness.
- 01Luo 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. Clin Nutr ESPEN 2025.
- 02Schwedhelm E et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol 2008.
Common questions
What is the difference between L-Arginine and L-Citrulline?
L-Arginine: Amino acid the body uses to make nitric oxide. In a meta-analysis, 4–24 g/day lowered blood pressure by about 5/3 mmHg. In a trial after heart attacks, more people died on arginine than on placebo, so it should not be used after a heart attack. L-Citrulline: Amino acid (named after watermelon) that the kidneys turn into arginine. It raises blood arginine more effectively than arginine itself, and in a meta-analysis it lowered blood pressure by about 4/3 mmHg in middle-aged and older adults.
Can I take L-Arginine and L-Citrulline together?
Yes — combining them lowered blood pressure more than citrulline alone in trials.