Ingredient Guide

L-Citrulline: A More Efficient Route to Nitric Oxide

L-citrulline is the amino acid many athletes reach for to feed the nitric-oxide pathway — and it does that job more efficiently than arginine itself, because more of it survives digestion and converts to arginine in the body. In training, its clearest role is helping you push out a few more reps before fatigue sets in.

  • Evidence-based
  • Structure/function only
  • No proprietary blends

What it is

L-citrulline is a non-essential amino acid, notably found in watermelon, sold as plain citrulline or as citrulline malate. The body converts it into arginine, which in turn feeds nitric-oxide production — making citrulline an indirect but more efficient way to support that pathway.

How it works

By raising circulating arginine, citrulline supports the nitric-oxide pathway involved in blood flow during exercise. In strength-training studies, citrulline malate has shown a small effect on delaying fatigue and increasing reps to failure, and it's been linked to lower perceived exertion and less next-day muscle soreness. The effects are modest and depend on an adequate pre-workout dose.

Why the form & source matter

Two common forms exist: plain L-citrulline and citrulline malate (citrulline bound to malic acid, the form used in much of the strength research). Doses in those studies are meaningful — several grams before training — so a token amount won't do much. As with arginine, this is a before-the-session ingredient, not an all-day one.

How Monthlees uses it

Monthlees includes citrulline in Oxyflow, its circulation-and-performance formula, where it sits alongside other nitric-oxide-pathway ingredients to support blood flow during exercise.

Frequently asked questions

Is citrulline better than arginine?

For raising arginine levels, citrulline is more efficient because more of it survives digestion.

What is citrulline malate?

Citrulline bound to malic acid — the form used in much of the strength-training research.

What does it do in training?

It's been shown to modestly delay fatigue and reduce perceived exertion and muscle soreness.

When do I take it?

Before a workout, at a meaningful dose of several grams.

Research & references

  1. Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis — International Journal of Sport Nutrition and Exercise Metabolism (2021) (source)
    Citrulline malate may delay fatigue and enhance muscle endurance during strength training.
  2. Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysis — Journal of Sport and Health Science (2020) (source)
    Citrulline reduced post-exercise RPE and muscle soreness.

References are provided for general educational context. They do not imply that this product treats, cures, or prevents any disease.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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Oxyflow™

Oxyflow™

400 mg L-citrulline DL-malate plus dual-form L-arginine — a nitric oxide support stack for circulation, blood flow, and workout performance.

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