Understanding the Differences: What Is the Best Form of Citrulline?

October 3, 2025 •

4 min read

Over a decade of research has solidified citrulline's reputation as a powerful performance-enhancing supplement. For many athletes, however, the question remains: what is the best form of citrulline, pure L-citrulline or citrulline malate, to best achieve their specific fitness objectives?

Quick Summary

The ideal citrulline supplement depends on your fitness priorities, with citrulline malate favored for comprehensive performance benefits and endurance, while pure L-citrulline excels at maximizing nitric oxide production for pumps.

Key Points

Citrulline Malate for Endurance: Citrulline Malate is favored for endurance and overall performance, boosting nitric oxide and ATP energy production.
L-Citrulline for Pumps: Pure L-citrulline effectively maximizes nitric oxide production, leading to increased blood flow and muscle pumps.
Dosage Varies by Form: Recommended dosages differ, typically 6-8g of CM or 3-6g of L-citrulline before a workout.
Ammonia Clearance Reduces Fatigue: Both forms help clear fatigue-causing ammonia via the urea cycle.
Recovery Benefits: Citrulline malate is linked to reduced post-exercise muscle soreness.
Better than L-Arginine: Citrulline raises plasma arginine levels more effectively than L-arginine, avoiding digestive issues.

The Science of Citrulline

Citrulline is a non-essential amino acid naturally produced by the body and found in foods like watermelon. Its two main roles relevant to exercise are supporting the urea cycle and being a precursor to nitric oxide.

The Nitric Oxide Pathway

Citrulline converts to L-arginine in the kidneys, which is then used to create nitric oxide (NO). NO is a vasodilator, relaxing blood vessels, which increases blood flow and improves oxygen and nutrient delivery to muscles during exercise. Citrulline is more effective at raising plasma arginine levels than arginine itself, as it avoids liver metabolism.

Clearing Metabolic Waste

High-intensity exercise produces ammonia, contributing to fatigue. Citrulline helps remove this ammonia through the urea cycle, potentially allowing for longer, more intense workouts.

L-Citrulline vs. Citrulline Malate: What’s the Difference?

The two main supplemental forms are L-citrulline and citrulline malate, differing in the addition of malic acid to the latter.

L-Citrulline: The Pure Form

This is pure citrulline, highly effective at boosting nitric oxide and blood flow, often chosen for maximizing muscle pumps and vasodilation.

Citrulline Malate: The Energizing Compound

Citrulline malate combines L-citrulline and malic acid. Malic acid is involved in the Krebs cycle, aiding aerobic energy production (ATP). This combination provides a potential dual benefit: the NO boost from citrulline and enhanced energy from malate, making it suitable for endurance and strength/stamina. Common citrulline to malate ratios are 2:1 and 1:1.

Performance Differences and Benefits

For High-Intensity Performance and Strength

Research suggests Citrulline Malate (CM) may offer a stronger overall effect for resistance training, potentially increasing repetitions and reducing muscle soreness due to improved nutrient delivery and enhanced energy production. While L-Citrulline also supports strength via improved blood flow and reduced fatigue, it lacks malic acid's direct energy benefit but is effective for a pure vasodilator effect.

For Endurance Training

Citrulline Malate (CM) is a strong option for endurance athletes due to malic acid's role in aerobic energy production. It may improve oxygen utilization and delay fatigue during prolonged exercise. Some studies show L-Citrulline can also improve oxygen kinetics and performance, although research is less consistent than for CM in this area.

Comparison: L-Citrulline vs. Citrulline Malate


Feature	L-Citrulline	Citrulline Malate
Composition	Pure L-citrulline amino acid.	L-citrulline bonded to malic acid.
Primary Goal	Maximize nitric oxide (NO) production and blood flow for muscle pumps.	Boost NO, enhance energy (ATP) production, and improve overall workout capacity.
Energy Boost	Minimal; benefits related to NO and ammonia buffering.	More pronounced, thanks to malic acid's role in the Krebs cycle.
Effect on Endurance	Improves oxygen utilization during high-intensity exercise.	More robust evidence for enhancing both aerobic and anaerobic endurance.
Effect on Recovery	Aids in ammonia detoxification, reducing fatigue.	Associated with a significant reduction in post-exercise muscle soreness.
Dosage (per serving)	Typically 3–6 grams for performance.	Typically 6–8 grams for performance (due to malate content).

Optimal Dosage and Timing

For performance, doses are usually taken 30–60 minutes pre-workout.

Citrulline Malate: 6–8 grams before exercise is common, with potentially greater effects at higher doses. Some take a smaller dose on non-training days.
L-Citrulline: 3–6 grams is standard for a pump focus. Doses of 6g or more daily for at least a week may be needed to significantly increase muscle oxygen content.

Potential Side Effects and Safety

Citrulline is generally safe and well-tolerated, with few reported side effects. Unlike high doses of L-arginine, it's better absorbed and less likely to cause digestive issues.

Safety points:

Blood Pressure: As it lowers blood pressure, those on blood pressure medication should monitor levels and consult a doctor.
Medication Interactions: Citrulline can interact with nitrates and ED drugs, potentially causing excessive blood pressure drops.
Pregnancy/Breastfeeding: Insufficient data exists; consult a healthcare provider.

How to Choose the Right Form

The best form depends on your goals. For endurance or a comprehensive boost in stamina, energy, and strength with reduced soreness, citrulline malate is often preferred due to malic acid. For maximum muscle pump and nitric oxide production focus, L-citrulline is highly effective.

L-citrulline may have more robust research for certain effects for beginners. Consider your needs and remember that diet and training are fundamental. For scientific reviews, see the National Institutes of Health: https://pmc.ncbi.nlm.nih.gov/articles/PMC8571142/.

Conclusion

Choosing between L-citrulline and citrulline malate depends on aligning the specific benefits of each with your fitness objectives. Both enhance nitric oxide and performance. However, citrulline malate offers broader benefits by aiding ATP production via malic acid, making it suitable for improved endurance and fatigue resistance. L-citrulline is excellent for maximizing blood flow and pumps. Both are proven, safe supplements to enhance workouts.

Frequently Asked Questions

While both increase nitric oxide, Citrulline Malate may offer a more noticeable pump due to the added energy benefits from malic acid.

Effects typically begin 30 to 60 minutes after taking it. More significant results may be noticed with consistent use over time.

Yes, it's generally safe to take citrulline on an empty stomach. Taking it before a workout may optimize absorption and benefits.

Citrulline is safe for most healthy adults at standard doses. Caution is advised for those on blood pressure or ED medications. Consult a doctor if pregnant or breastfeeding.

L-citrulline converts to L-arginine, which produces nitric oxide. Citrulline is better absorbed and leads to higher, more sustained arginine levels than direct L-arginine supplementation.

Yes, citrulline malate is linked to improved recovery and can significantly reduce muscle soreness after intense exercise, possibly due to better blood flow and waste removal.

Endurance athletes typically benefit more from citrulline malate, as it enhances both oxygen delivery (citrulline) and energy production (malic acid) for sustained performance.