Quick answer: L-citrulline is a nonessential amino acid that the body can convert to arginine; arginine can then contribute to nitric-oxide production. This pathway is a reason citrulline is studied in exercise nutrition. The NIH Office of Dietary Supplements finds the research on citrulline for exercise performance limited and conflicting, so an ingredient mechanism is not proof that a particular pre-workout will create a pump, improve blood flow, or improve performance.
What Is L-Citrulline?
L-citrulline is made in the body and is also found in foods, including watermelon. The body converts much of its citrulline to arginine in the kidneys. Arginine can be used in nitric-oxide pathways.
This describes a biological pathway. It does not establish a cardiovascular, blood-pressure, blood-flow, pump, or training outcome from a specific supplement.
Citrulline, Arginine, and Nitric Oxide
The relationship between citrulline, arginine, and nitric oxide is why these ingredients appear in pre-workout formulas. The NIH notes that citrulline may raise blood arginine more efficiently than oral arginine in some contexts because more citrulline is absorbed from the gut.
That mechanism still leaves an important product question: what exact form, amount, timing, and population did a study evaluate? Do not combine label amounts from different ingredients and call the total a clinically established dose without evidence for that exact combination.
What Research Suggests About Exercise
Most exercise studies discussed by the NIH used citrulline malate, while some used L-citrulline alone. The NIH describes the research as limited and conflicting, and says it does not provide strong support for using citrulline or citrulline malate to enhance exercise or athletic performance.
That does not make citrulline an illegitimate ingredient. It means the evidence does not justify a product-level promise of a better pump, more repetitions, faster times, or reduced soreness.
Dosage and Form: What to Compare
L-citrulline and citrulline malate are different labeled materials. A cited study may use one form, a particular amount, and a particular timing protocol. Compare those details with the Supplement Facts panel rather than assuming that every citrulline amount is interchangeable.
The NIH summarizes studies using, for example, 8 g citrulline malate before a lifting test and 3 g or 9 g L-citrulline in a treadmill study. Those different findings are part of why a single generic dose claim would overstate the evidence.
Safety and Practical Considerations
The NIH reports few safety concerns in short-term studies, while noting that research has not adequately assessed long-term supplemental use. Gastrointestinal discomfort has been reported in some studies.
If you take medication, have a medical condition, are pregnant or nursing, or have questions about supplement use, ask a qualified clinician before using one.
L-Citrulline in PurePump®
Product: PurePump® Pre-Workout
Label amount: 2,000 mg L-citrulline plus 500 mg L-arginine per 2-scoop serving (7.7 g)
Servings per container: 30
PurePump lists 2 g L-citrulline and 500 mg L-arginine separately. It does not use citrulline malate. The NIH summarizes different study examples: 8 g citrulline malate before a lifting test, and 3 g or 9 g L-citrulline in a treadmill study. Those are different forms and study designs, so they are context for label reading rather than an equivalence threshold for this formula.
Do not add the two ingredients together and present 2.5 g as an established nitric-oxide or performance dose. The label tells you what is present; the current evidence does not establish the outcome of this exact formula and amount.
PurePump is unflavored and bitter. Mix it with a beverage you already use; a smaller, shot-like amount of liquid and a citrusy, sour juice or sports drink can help balance the bitterness.
A batch-specific third-party record must be matched to the lot on the product before it is used as evidence for that product. It does not verify a product-level blood-flow, pump, or performance result.
View the September 2026 PurePump Unflavored lot-797797 BSCG certificate →
FAQ
Is L-citrulline the same as citrulline malate?
No. Citrulline malate combines citrulline with malic acid. Compare the form and amount on a product label with the form and amount used in the specific study you are reading.
Does L-citrulline increase nitric oxide?
L-citrulline can be converted to arginine, and arginine participates in nitric-oxide pathways. That mechanism does not establish a particular outcome from a product or serving.
When should I take L-citrulline?
Study timing varies by study design and form. Follow a product's label directions and avoid treating a timing claim from one study as a guarantee for a different formula.
Is L-citrulline safe?
The NIH reports few safety concerns in short-term studies but notes limited long-term supplemental safety data. Discuss supplement use with a qualified clinician if you have relevant health or medication questions.
Why is L-citrulline in PurePump?
PurePump lists 2,000 mg L-citrulline and 500 mg L-arginine per full serving. The separate amounts let you compare the formula with the research and decide whether it fits your own priorities.
Sources and related reading
- NIH Office of Dietary Supplements: Exercise and athletic performance
- PurePump Supplement Facts
- What is beta-alanine? →
- How to read a proprietary blend →
These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.