Citrulline Malate: What It Is and How It Works
Citrulline malate is a staple of American pre-workout formulas, credited with better "pumps," extra reps, and less soreness. Unlike many trendy ingredients, it has a plausible mechanism and a reasonable body of research behind it. Our editorial team explains what this compound is, how it works in the body, and what results you can realistically expect.
What citrulline malate is
L-citrulline is a non-essential amino acid. The body makes it in the gut and in the urea cycle, and it is also found in foods, most famously watermelon, whose Latin name Citrullus gave the compound its name. Unlike most amino acids, citrulline is not used to build proteins.
Citrulline malate (CM) combines L-citrulline with malic acid, an intermediate of the Krebs cycle that also gives apples their tart flavor. Common supplement ratios are 2:1 and 1:1 citrulline to malate, which means that a given scoop of CM contains less citrulline than the same weight of pure L-citrulline.
The compound has a medical history: in parts of Europe, citrulline malate has been sold for decades as a remedy for fatigue. In the U.S., both L-citrulline and citrulline malate are sold as dietary supplements.
Understanding the ratio is essential when comparing products. A label listing 6 grams of 2:1 citrulline malate provides about 4 grams of citrulline, while a 1:1 product provides roughly 3 grams.
The nitric oxide pathway
Citrulline's main claim to fame is its effect on nitric oxide (NO), a signaling molecule that relaxes blood vessels and influences blood flow, muscle contraction, and mitochondrial function. NO is produced from arginine by enzymes called nitric oxide synthases.
It would seem logical simply to take arginine. However, oral arginine is heavily broken down in the gut and liver before it reaches the circulation. Citrulline bypasses this: it is absorbed well and converted into arginine mainly in the kidneys, raising blood arginine more effectively.
Schwedhelm and colleagues demonstrated this in 2008, showing that oral citrulline increased plasma arginine and markers of NO production more efficiently than arginine itself. This is why many formulas have replaced arginine with citrulline.
Citrulline also plays a role in clearing ammonia through the urea cycle. Since ammonia accumulates during intense exercise and is associated with fatigue, this is another proposed mechanism for its benefits.
What malate adds
Malic acid participates in the Krebs cycle, the series of reactions that cells use to produce energy aerobically. The theory is that extra malate could support energy production during exercise, complementing citrulline's effects.
An early study by Bendahan and colleagues using magnetic resonance spectroscopy found that citrulline malate increased the rate of oxidative ATP production and phosphocreatine recovery after exercise in a small group of men who reported fatigue.
However, it remains unclear how much malate itself contributes, as few studies have compared pure citrulline with citrulline malate head-to-head in trained athletes. The malate component may be helpful, neutral, or simply a byproduct of how the product was historically formulated.
From a practical viewpoint, what matters is the total citrulline dose and consistent evidence of performance effects, rather than the malate theory alone.
What the research shows
Interest in CM for strength training surged after a 2010 study by Pérez-Guisado and Jakeman. Participants given 8 grams of citrulline malate one hour before a bench press workout completed more repetitions and reported less muscle soreness over the next days than those given placebo.
Subsequent studies produced mixed results. Wax and colleagues found more repetitions in lower-body exercises in advanced lifters, while other trials found no meaningful effect. A 2019 meta-analysis by Trexler and colleagues concluded that citrulline produced a small but statistically significant improvement in high-intensity strength and power performance.
Research suggests the following potential outcomes, ranked by strength of evidence:
- slightly more repetitions to failure in resistance training;
- reduced perceived exertion and muscle soreness in some studies;
- possible improvement in blood flow and the sensation of a "pump";
- inconsistent effects on endurance performance.
| Outcome | Evidence quality | Size of effect |
|---|---|---|
| Reps to failure | Moderate | Small |
| Muscle soreness | Limited to moderate | Small, variable |
| Endurance performance | Limited | Inconsistent |
| Blood flow / pump | Limited | Subjective, variable |
Practical use and safety
Most performance studies used 6–8 grams of citrulline malate (often 2:1), taken about 60 minutes before exercise. If you use pure L-citrulline, around 3–6 grams provides a comparable amount of citrulline. Many pre-workout products contain far less than these amounts, so check labels carefully.
Some people take citrulline daily rather than only before training, since blood arginine levels may benefit from regular intake. Both approaches have been studied, and neither is clearly superior for all goals.
Citrulline is generally well tolerated. Stomach discomfort can occur at higher doses, especially on an empty stomach. Because it can lower blood pressure slightly, people taking blood pressure medications, nitrates, or erectile dysfunction drugs such as sildenafil should speak with a physician before use.
Pregnant or breastfeeding women and people with kidney disease should also seek medical advice first. As with all supplements, third-party tested products help ensure label accuracy.
Editorial Team Conclusions
Citrulline malate is one of the better-supported pre-workout ingredients. It raises arginine more effectively than arginine itself and can yield small improvements in high-repetition strength work, with possible benefits for soreness.
The effects are modest, so it works best as a complement to sound training, nutrition, and sleep rather than as a game-changer. Pay attention to the citrulline-to-malate ratio and use the doses that were actually tested.
Related topics you might find useful: our articles on beta-alanine and muscular endurance, on dietary nitrates from beetroot, and on how to evaluate pre-workout supplement labels.
References
- Pérez-Guisado J, Jakeman PM. Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. J Strength Cond Res. 2010;24(5):1215–1222.
- Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol. 2008;65(1):51–59.
- Bendahan D, Mattei JP, Ghattas B, Confort-Gouny S, Le Guern ME, Cozzone PJ. Citrulline/malate promotes aerobic energy production in human exercising muscle. Br J Sports Med. 2002;36(4):282–289.
- Wax B, Kavazis AN, Weldon K, Sperlak J. Effects of supplemental citrulline malate ingestion during repeated bouts of lower-body exercise in advanced weightlifters. J Strength Cond Res. 2015;29(3):786–792.
- Trexler ET, Persky AM, Ryan ED, Schwartz TA, Stoner L, Smith-Ryan AE. Acute effects of citrulline supplementation on high-intensity strength and power performance: a systematic review and meta-analysis. Sports Med. 2019;49(5):707–718.
- Gonzalez AM, Trexler ET. Effects of citrulline supplementation on exercise performance in humans: a review of the current literature. J Strength Cond Res. 2020;34(5):1480–1495.
