L-Citrulline

Your intake

What each level of l-citrulline does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

1. Severely lowYOU ARE HERE

   0 g – 1.98 g

   Well below target. Risk of deficiency symptoms tied to endurance · pump.

2. Insufficient

   1.98 g – 6 g

   Below the recommended daily target. Long-term adequacy not assured.

3. Adequate

   6 g – 9 g

   Daily target met. Standard nutritional support for endurance · pump.

4. Therapeutic

   9 g – 12 g

   Common for specific health goals. Check the evidence for your situation before sustaining this level.

5. Diminishing returns

   12 g – +

   Past the point where extra intake typically helps. Evidence for further benefit is thin.

Overview

Non-protein amino acid that bypasses intestinal and hepatic arginase first-pass, raising plasma arginine more reliably than oral arginine itself. Found in watermelon (especially rind). The preferred path to NO-mediated vascular and exercise benefits.

Functions

• ●Converted to arginine in kidneys (citrulline-arginine cycle)
• ●Indirect NO synthesis substrate
• ●Participates in urea cycle (ammonia detoxification)
• ●Reduces blood ammonia accumulation during prolonged exercise

Mechanism

Oral citrulline is absorbed without significant first-pass metabolism, reaches kidneys, and is converted to arginine by argininosuccinate synthase and lyase. The resulting plasma arginine sustains higher levels for longer than equimolar oral arginine. Citrulline malate adds malate, a TCA cycle intermediate, potentially supporting ATP regeneration during exercise.

Benefits

• ●Increases reps and reduces post-exercise soreness (citrulline malate, 6–8 g)
• ●Modestly improves erectile function (lower-grade vs PDE-5 inhibitors)
• ●Reduces blood pressure modestly in metabolic syndrome
• ●Pre-workout 'pump' on more solid footing than arginine

Deficiency

Not an essential amino acid; no deficiency state. The relevant 'low' state is inadequate dietary arginine/citrulline in disease states that depress NO signalling.

Excess

Well-tolerated. GI distress at multi-gram doses is the typical ceiling. No UL.

Forms

• L-citrulline (free form)
  Cleaner pre-workout; 3–6 g; well-tolerated
• Citrulline malate (1:1 or 2:1)
  Adds malate; classic exercise-performance form; 6–8 g (note: 6 g malate = 4 g citrulline at 2:1)
• Watermelon / rind
  Whole-food source; modest doses without supplementation

Food sources

• Watermelon (especially rind) · 1 cup0.5–1.5 g
• Pumpkin · 1 cup cooked0.3 g
• Bitter melon · 1 cup0.4 g
• Cucumber · 1 cup0.05 g

Supplement forms

L-citrulline (free form) at 3–6 g, or citrulline malate at 6–8 g, 60 minutes pre-workout. Free-form L-citrulline is the cleaner pick if you don't need malate. Doses above 10 g cause GI distress for many.

Bioavailability

~80% oral bioavailability; minimal first-pass hepatic metabolism. Peak plasma at ~60 minutes. Renal conversion to arginine continues for 4–6 hours, sustaining higher plasma arginine than oral arginine.

Longevity relevance

Vascular endothelial function declines with age; supporting NO signalling is relevant to healthspan. Citrulline (or food-sourced arginine + citrulline) is the more practical NO-raising tool in healthy older adults vs arginine.

Relationships

References

• Examine — Citrullinereview
• Schwedhelm — citrulline vs arginine on plasma arginine (Br J Clin Pharmacol 2008)study
• Trexler — citrulline malate and exercise meta-analysis (Eur J Sport Sci 2019)review

About L-Citrulline

Converted to arginine; sustained NO support, exercise performance. Common dose 3–8 g.

Role

Endurance · pump

Daily target

6 g (TR)

Also called

l-citrulline, citrulline, citrulline malate