Citrulline malate (CM) is a popular supplement used to enhance exercise performance by improving blood flow and reducing muscle fatigue. It is formed by combining the amino acid L-citrulline with malic acid. CM functions as a precursor to L-arginine, which is converted into nitric oxide (NO), a molecule that signals blood vessels to widen. Understanding the time course of CM’s action, from ingestion to biological clearance, is necessary to use it effectively.
Time to Peak Absorption
Citrulline Malate requires time to be absorbed and metabolized before it begins to influence performance. After consumption, L-citrulline is absorbed from the gut and travels to the kidneys, where it is converted into L-arginine. This conversion process leads to higher and more sustained plasma L-arginine levels.
The time it takes to reach the maximum concentration of L-citrulline in the blood plasma (Tmax) typically occurs between 60 and 120 minutes following oral intake. Since performance benefits are tied to the rise in L-arginine and nitric oxide levels, the peak effect on NO production aligns with this timeframe. Acute studies often use a timing of one hour before exercise to maximize circulatory levels during the workout.
The Effective Window of Performance
The functional benefit of Citrulline Malate is directly related to elevated nitric oxide levels, which promotes vasodilation. This effect increases blood flow to working muscles, delivering more oxygen and nutrients while assisting in the removal of metabolic byproducts like ammonia. The period when these physiological effects are strong enough to enhance exercise performance is considered the effective window.
The performance-enhancing effects generally begin to manifest around the time of peak plasma concentration, approximately 60 to 90 minutes after consumption. This window of effectiveness can last for an additional 1.5 to 2 hours of sustained activity. As the concentration of L-citrulline declines from its peak, the magnitude of the NO-mediated benefits, such as improved endurance, will also diminish.
Biological Clearance and Half-Life
The biological duration of Citrulline Malate in the body is distinct from its effective window of performance. The half-life of L-citrulline is generally considered to be in the range of several hours, which is longer than the acute performance benefit.
The kidneys play a primary role in the clearance and metabolism of L-citrulline, converting a portion to L-arginine and filtering the rest for excretion. Although L-citrulline may remain present in the bloodstream for an extended period, its concentration will eventually drop below the threshold required to produce a significant ergogenic effect. Research suggests that a single dose can elevate plasma levels for up to 24 hours, but the highest functional impact is limited to the initial few hours following the peak.
Guidance on Optimal Timing
To maximize the performance benefits of Citrulline Malate, consumption timing should align with the substance’s pharmacokinetic profile. The most effective strategy is to consume the recommended dosage of 6 to 8 grams approximately 60 to 90 minutes before exercise. This timing ensures that the body’s nitric oxide levels are at their highest concentration as the workout begins.
Consuming the supplement with food can sometimes delay the absorption rate, potentially shifting the time to peak concentration later than the typical 90-minute mark. To maintain consistently elevated plasma L-arginine levels, some individuals split their daily dose or engage in a short-term “loading” phase. Daily consumption, even on rest days, helps sustain the amino acid concentration for overall cardiovascular health and recovery.