Citrulline malate is a supplement that combines the amino acid citrulline with malic acid, and it works through two parallel pathways: boosting nitric oxide production to improve blood flow, and supporting your body’s energy and waste-clearing systems during exercise. A meta-analysis of resistance training studies found that taking 6 to 8 grams before a workout increased repetitions to failure by about 6.4% compared to a placebo. The effect is modest but consistent, which is why citrulline malate has become one of the more popular ingredients in pre-workout supplements.
How It Increases Blood Flow
Citrulline is a non-essential amino acid that your body converts into arginine, which is the direct building block for nitric oxide. Nitric oxide relaxes blood vessel walls, allowing them to widen and carry more blood to working muscles. What makes citrulline unusual is that it bypasses the liver during digestion, so more of it reaches your bloodstream intact compared to taking arginine directly. Oral citrulline supplementation reliably raises plasma arginine levels, and when arginine availability is limited, citrulline can restore nitric oxide production.
This improved blood flow matters during exercise because it helps deliver oxygen and nutrients to muscles while clearing metabolic waste products more efficiently. The “pump” feeling many people report from citrulline malate is a direct result of this vasodilation.
How It Supports Energy Production
The malate half of citrulline malate plays its own distinct role. Malic acid is an intermediate in the Krebs cycle, the process your mitochondria use to generate energy. By feeding additional malate into this cycle, the supplement may help sustain aerobic energy production during prolonged or intense effort. Malate also contributes to reducing lactic acid buildup, which means the “burning” sensation in your muscles during hard sets may take slightly longer to set in.
Meanwhile, citrulline itself helps manage ammonia, a toxic byproduct that accumulates in muscles during high-intensity work. Ammonia interferes with your muscles’ ability to burn fuel efficiently, accelerating fatigue. Citrulline is a key component of the urea cycle in the liver, the system responsible for converting ammonia into urea so it can be excreted. Animal studies have shown that citrulline supplementation suppresses the rise in blood ammonia during exhaustive exercise and also lowers blood lactate levels. The combination of better ammonia clearance and sustained energy production is what gives citrulline malate its anti-fatigue reputation.
Effects on Strength and Reps
The most well-documented benefit is a small increase in the number of reps you can perform during resistance training. A systematic review and meta-analysis found that 6 to 8 grams taken 40 to 60 minutes before exercise resulted in roughly 3 extra repetitions across multiple sets to failure, translating to that 6.4% average improvement. The effect tends to show up more in later sets, when fatigue has accumulated. In one study, bench press performance in the first two sets was similar between citrulline malate and placebo groups, but sets three and four showed a clear advantage for the supplement group.
The benefits extend across different exercises. Studies have found increased total reps in chin-ups, reverse chin-ups, push-ups, leg presses, and bench presses when using citrulline malate. That said, expressed as effect sizes (a statistical measure of how meaningful the difference is), the improvements ranged from 0.23 to 0.59, which researchers describe as small to moderate. Citrulline malate won’t transform your training, but it can give you a few extra reps at the tail end of hard sets, and those reps add up over weeks and months.
Impact on Muscle Soreness
One frequently cited study found that citrulline malate reduced muscle soreness by 40% at both 24 and 48 hours after an intense chest workout, with over 90% of participants reporting a noticeable reduction. This is likely tied to improved blood flow aiding recovery and more efficient clearance of metabolic byproducts that contribute to delayed-onset soreness. While this is a promising finding, it comes from a single well-known study, so the magnitude of the effect may vary in practice.
Citrulline Malate vs. Plain L-Citrulline
A common question is whether the malate component actually matters, or whether plain L-citrulline works just as well. A double-blind, placebo-controlled trial compared 8 grams of L-citrulline to 12 grams of citrulline malate (which delivers a similar amount of actual citrulline) over six weeks of resistance training. The conclusion: both forms enhanced upper-body muscular endurance and post-exercise nitric oxide response, with no measurable difference between them.
This suggests that citrulline is doing the heavy lifting in the combination, and the malate component may play a supporting but not essential role. If you choose plain L-citrulline, you can use a slightly lower dose since you’re getting pure citrulline without the added malic acid weight. Most citrulline malate products use a 2:1 ratio, meaning two parts citrulline to one part malate, so 6 grams of citrulline malate delivers about 4 grams of actual citrulline.
What It Does Not Do
Despite the nitric oxide mechanism, citrulline does not appear to lower blood pressure in a clinically meaningful way. A study examining six days of L-citrulline supplementation in older men found no significant effect on resting blood pressure, arterial stiffness, or blood vessel elasticity, either at rest or during exercise. Other studies in different populations have shown similarly underwhelming results for cardiovascular markers. The blood flow improvements seem to matter more during active exercise than as a passive cardiovascular benefit.
Dosing and Timing
The most studied dose is 6 to 8 grams of citrulline malate, taken 40 to 60 minutes before training. This timing allows citrulline to be absorbed and converted into arginine before your workout begins. If you’re using plain L-citrulline instead, 4 to 6 grams provides a comparable amount of the active amino acid.
Some people experience mild stomach discomfort at higher doses, particularly on an empty stomach. Starting with 4 to 6 grams and increasing from there is a reasonable approach if you’re trying it for the first time. Citrulline malate has a noticeably sour taste due to the malic acid, which is why most people take it mixed into a flavored drink rather than on its own.