Citrulline
Also known as: L-Citrulline, Citrulline Malate, CM, L-Cit
Effective Dosage
No established dose from provided studies alone; study doses vary widely
What the Science Says
Citrulline is a non-essential amino acid found naturally in watermelon and produced in the body. It acts as a precursor to arginine, which the body uses to make nitric oxide — a molecule that relaxes and widens blood vessels. The strongest clinical evidence from provided studies supports its ability to significantly reduce blood pressure spikes caused by cold exposure (by roughly 9 mmHg systolic), and emerging research suggests it may support endothelial function and blood glucose management in people with type 2 diabetes. When combined with HIIT exercise, citrulline supplementation may also influence muscle-related biological markers, though the practical muscle-building benefit remains exploratory.
What It Doesn't Do
Won't dramatically boost gym performance on its own — one RCT found no significant improvement in aerobic, anaerobic, or CrossFit performance with a combined arginine and citrulline malate dose. Not a proven muscle-builder. Not a substitute for exercise. Don't expect overnight results — most benefits appear over weeks of consistent use. No solid evidence it burns fat or speeds up recovery on its own.
Evidence-Based Benefits
May improve blood flow and exercise performance. Better absorbed than L-arginine.
Moderate EvidenceEffective at: 6-8g L-citrulline OR 8-10g citrulline malate
Source: Examine.com
Absorption & Bioavailability
Good — citrulline is more efficiently converted to arginine (and thus nitric oxide) than arginine itself when taken orally, because it bypasses first-pass liver metabolism. However, specific bioavailability data were not reported in the provided abstracts.
Red Flags to Watch For
- Acute single-dose supplementation (pre-workout) may not provide meaningful ergogenic benefits based on available RCT data — don't expect a dramatic performance boost from one serving
- Most dramatic effects (e.g., blood pressure reduction in cold) are from small pilot trials with 162 or fewer participants — results may not generalize broadly
- Animal study data (testicular injury model) cannot be directly applied to human supplement use
- Citrulline malate products vary widely in citrulline-to-malate ratios — check labels, as some products are mostly malate filler
- People on blood pressure medications should consult a doctor before use, as additive blood pressure lowering could occur
Products Containing Citrulline
See how Citrulline is used in these analyzed products:
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06