What Is Citrulline?
L-citrulline is an essential amino acid that converts into L-arginine in the body — the main raw material for nitric oxide (NO) production. NO dilates blood vessels and improves blood flow, oxygen and nutrient delivery to muscles. Paradoxically, citrulline supplements increase arginine levels in the blood more effectively than arginine supplements themselves, because citrulline bypasses liver metabolism.
📊 Citrulline Forms: Which to Choose?
| Form | Purity | Main benefit | Recommendation |
|---|---|---|---|
| L-Citrulline (Pure) | 100% | NO production, blood flow | Best NO |
| Citrulline Malate (2:1) | ~57% citrulline | NO + ATP energy | Best for Sports |
| Citrulline Nitrate | ~65% | Double NO (citrulline+nitrates) | For Advanced |
| Arginine-Citrulline Complex | Various | General NO Support | Less effective |
🧪 What Science Says: Key Studies
💪 Strength Endurance
8 g of citrulline malate before training increased the number of bench press repetitions and reduced muscle soreness over 48 hours.
🫀 Blood Flow and Pump
Citrulline significantly increases arginine levels in the blood, which stimulates NO production. The result is better blood flow and muscle fullness (pump effect).
🧹 Ammonia Removal
Citrulline participates in the urea cycle and helps remove ammonia — one of the main causes of fatigue. Less ammonia = less fatigue.
🏃 Aerobic Endurance
Citrulline supplements may improve VO2 max and reduce time to exhaustion during long-distance events, especially in hot conditions.
📋 Dosage Recommendations
- Citrulline Malate (for Sports): 6–8 g 45–60 min before training
- L-Citrulline (for NO Booster): 3–6 g per day, preferably before training
- For Endurance Sports: 8–10 g citrulline malate before competition
- For general blood flow improvement: 2–4 g L-citrulline daily
- Do not exceed: 15 g per day (may cause digestive upset)
🏋️ Citrulline by Sport
- Strength sports / bodybuilding: 6–8 g citrulline malate before training — maximum pump effect and strength endurance
- Endurance sports: 8–10 g before long distances. Better blood flow, less fatigue
- HIIT / CrossFit: 6 g before training. Better recovery between intense intervals
- Team sports: 4–6 g before competition. Better endurance in the second half of the match
🔄 Citrulline Synergy with Other Supplements
- Citrulline + Beta-Alanine: One of the best combinations for endurance. Beta-alanine buffers acids in muscles, while citrulline improves blood flow. Together they allow you to train longer and more intensely.
- Citrulline + Creatine: Citrulline improves creatine transport into muscles due to improved blood flow. There is some data on a synergistic effect.
- Citrulline + Nitrates (beetroot): Double NO pathway — citrulline via the arginine-NO pathway, nitrates via the nitrate-nitrite-NO pathway. Maximum vasodilation.
💡 Practical Citrulline Use
⏰ When to Drink?
Optimal time — 45–60 min before training. The effect of citrulline begins after ~45 min and lasts 2–3 hours. For longer workouts, the dose can be split.
🍉 Natural Source
The name citrulline comes from the Latin name for watermelon (Citrullus). Watermelons contain a fair amount of citrulline (2 mg/g), but to get 6 g you would need to eat ~3 kg of watermelon.
Additional Tip:
If you feel tingling in your skin after citrulline — don't worry. This is a common side effect related to improved peripheral blood circulation. It is harmless and usually disappears within 30 min.
❓ Frequently Asked Questions
How does citrulline differ from arginine?
Arginine is a direct raw material for NO production, but most of the consumed arginine is broken down in the liver. Citrulline bypasses this process — it is converted to arginine in the kidneys and enters the bloodstream directly. Therefore, citrulline supplements more effectively increase arginine concentration in the blood.
Does citrulline help with erections?
NO is the main molecule responsible for blood vessel dilation, including penile blood vessels. As a result, citrulline may have a positive effect on erection quality, but this is not its primary purpose.
Can It Be Used Daily?
Yes. Citrulline is safe for daily use up to 15 g per day. Most athletes use it only on training days, but daily use in lower doses (3–4 g) can support better blood circulation.