L-Citrulline
The nitric oxide booster that enhances blood flow, pumps, and endurance
Also known as: Citrulline • Citrulline Malate • L-Citrulline DL-Malate
Overview
L-Citrulline is a non-essential amino acid named after watermelon (Citrullus lanatus), its richest natural source. In the body, citrulline is converted to L-arginine in the kidneys, which is then converted to nitric oxide (NO) — a molecule that relaxes blood vessels and improves blood flow. Paradoxically, supplementing with citrulline raises blood arginine levels more effectively than supplementing with arginine directly, because arginine is heavily metabolized during first-pass liver metabolism while citrulline bypasses this. The result is improved blood flow, better exercise performance, reduced fatigue, and enhanced recovery. Citrulline also plays a role in the urea cycle, helping remove ammonia — a metabolic waste product that contributes to fatigue during exercise. It's available as pure L-citrulline or as citrulline malate (combined with malic acid), both of which are effective.
Key Benefits
Nitric Oxide & Blood Flow
Citrulline is the most effective oral supplement for increasing nitric oxide production. It raises plasma arginine levels by 227% (more than arginine supplementation itself), leading to vasodilation, improved blood flow, and reduced blood pressure.
Exercise Performance
Multiple studies show citrulline malate improves resistance training performance by 1-3 additional reps per set, increases time to exhaustion in endurance exercise, and reduces perceived exertion during high-intensity training.
Reduced Muscle Soreness
A landmark study found that 8g citrulline malate reduced post-exercise muscle soreness by 40% at 24 and 48 hours compared to placebo, likely through improved blood flow and ammonia clearance.
Blood Pressure Support
Meta-analyses show citrulline supplementation reduces systolic blood pressure by 4-6 mmHg and diastolic by 2-4 mmHg, with effects comparable to some first-line antihypertensive medications.
Dosage & How to Take
6-8g L-citrulline or 8-10g citrulline malate pre-workout
| Purpose | Dose | Notes |
|---|---|---|
| Exercise performance | 6-8g L-citrulline | 30-60 min pre-workout |
| Blood pressure support | 3-6g/day | Can be split into 2 doses |
| General health / blood flow | 3g/day | Minimum effective dose |
Best Time to Take
30-60 minutes before exercise for performance benefits. For blood pressure, timing is less important — consistency matters more.
With or Without Food
Can be taken on an empty stomach. Mixing with a pre-workout drink is common.
Forms & Bioavailability
| Form | Absorption | Best For | Notes |
|---|---|---|---|
| L-Citrulline (pure) | High | Most efficient — 100% citrulline by weight | Preferred form for precise dosing |
| Citrulline Malate 2:1 | High | Combined with malic acid for additional energy cycle support | Only ~66% citrulline by weight — need higher doses |
| Citrulline Malate 1:1 | High | Equal ratio formulation | 50% citrulline by weight |
Side Effects & Safety
Common
- Mild GI discomfort at very high doses
- Possible heartburn
Rare
- None significant
Contraindications
- PDE5 inhibitors (Viagra, Cialis) — additive blood pressure lowering
- Nitrate medications
Interactions
Additive blood pressure lowering effect
Both increase nitric oxide — may cause excessive blood pressure drop
Scientific Research
Citrulline Malate and Resistance Training
8g citrulline malate increased total reps performed by 52.92% and reduced soreness by 40% at 24 and 48 hours
Citrulline and Blood Pressure
Meta-analysis of 7 trials: citrulline reduced systolic BP by 4.1 mmHg and diastolic by 2.1 mmHg
Food Sources
Frequently Asked Questions
Medical Disclaimer
This content is for educational and informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional before starting any supplement regimen, especially if you have pre-existing health conditions or are taking medications. The statements on this page have not been evaluated by the Food and Drug Administration.