How Much L-Citrulline Should Be In Your Preworkout?

Research on L-citrulline uses roughly 6 to 8 grams of pure L-citrulline, or about 8 grams of citrulline malate, taken 40 to 60 minutes before training. Most preworkouts on the shelf use a fraction of that, which is the first thing worth knowing before you judge whether yours is doing anything.

That is the short answer. The longer answer is more honest than most supplement pages will be with you, because the research on citrulline is a mix of real effects and overstated ones, and you deserve both halves.

What does L-citrulline actually do?

Citrulline is a precursor to arginine, the raw material your body uses to make nitric oxide, which relaxes blood vessels. The interesting part is that taking citrulline raises blood arginine more effectively than taking the same kind of dose of arginine itself. In a controlled dose-ranging trial, oral L-citrulline increased plasma arginine better than oral L-arginine, at smaller doses (Schwedhelm et al., 2008). That is why serious formulas use citrulline instead of arginine.

It also does move the nitric oxide pathway in humans. A 6 gram dose raised exhaled nitric oxide by about 19 percent (Theodorou et al., 2021). So the mechanism is real. Whether that mechanism turns into something you feel in a single session is a separate question, which we will get to.

Why does the dose matter so much?

Because the benefits that do show up in research showed up at specific doses. The studies used about 6 to 8 grams of L-citrulline or roughly 8 grams of citrulline malate (Suzuki et al., 2016; Glenn et al., 2017; Perez-Guisado and Jakeman, 2010). If a label lists citrulline but the dose is one or two grams, or hides it inside a proprietary blend so you cannot see the number at all, you are below what the research actually tested. The ingredient being present is not the same as the ingredient being dosed.

Does citrulline actually improve your workout?

Here is where honesty matters. The evidence is genuinely mixed, and anyone who tells you it is settled is selling something.

The most consistent finding is not raw strength. It is recovery and effort. A meta-analysis of 13 randomized controlled trials covering 206 people found that citrulline modestly reduced perceived exertion and muscle soreness at 24 and 48 hours after training, with the effect fading by 72 hours (Rhim et al., 2020). Pooled across many studies, that is the most trustworthy claim you can make.

Reps and strength are less clear. Two acute 8 gram studies found more reps, one in trained women on bench and leg press (Glenn et al., 2017) and a well-known one in men that reported about 53 percent more bench reps and lower soreness (Perez-Guisado and Jakeman, 2010). But two other randomized, double-blind trials using the same 8 gram dose found no improvement in reps at all (Gonzalez et al., 2018; Chappell et al., 2018). Same dose, opposite results. The honest read is that some people respond and some do not, and the rep benefit is not something you should count on.

For endurance, a single solid trial found that L-citrulline cut 4 kilometer cycling time trial time by 1.5 percent and raised power output by about 2 percent (Suzuki et al., 2016). That is real, but it is one study, so treat it as early evidence rather than proof.

What about that famous "40 percent less soreness" number?

You will see it everywhere. It comes from one study (Perez-Guisado and Jakeman, 2010), and it deserves a caveat that supplement marketing never gives it. The two training sessions in that study ran on consecutive days with no confirmed washout period, which is a real methodological weakness. Its effect sizes are also unusually large compared to everything published since. And in the other direction, one trial found citrulline malate actually made soreness worse over the following days (Chappell et al., 2018). So the defensible claim is the meta-analysis: a modest reduction in soreness on average, not a guaranteed 40 percent.

Will I feel a bigger pump?

Maybe, maybe not, and the research does not let us promise it. Nitric oxide markers go up (Theodorou et al., 2021), but in that same study the rise did not translate into measurably better muscle oxygenation or performance. A biomarker moving is not the same as a pump you can see in the mirror. Some people clearly feel it. The literature does not consistently confirm it as a universal effect.

What should you look for on a preworkout label?

• A disclosed citrulline dose in the 6 to 8 gram range, printed as an actual number.
• No proprietary blend hiding the amount. If you cannot see the dose, assume it is underdosed.
• Clarity on the form. Citrulline malate is citrulline bound to malic acid, so 8 grams of citrulline malate contains less pure citrulline than 8 grams of L-citrulline. Both forms appear in the research; just know which one you are getting.

For the record, Adonis Complex PRE lists 10 grams of L-citrulline on the label, above the common research range and fully disclosed. You can read the full label here if you want to see how it is dosed.

FAQ

How much L-citrulline should a preworkout have?
Research uses about 6 to 8 grams of L-citrulline, or roughly 8 grams of citrulline malate, taken 40 to 60 minutes before training (Suzuki et al., 2016; Glenn et al., 2017).

Is citrulline better than arginine?
For raising blood arginine and nitric oxide, yes. Oral citrulline raised plasma arginine more effectively than oral arginine in a controlled trial (Schwedhelm et al., 2008).

Does citrulline actually reduce soreness?
On average across many studies, modestly, at 24 to 48 hours (Rhim et al., 2020). Individual results vary, and at least one study found no benefit, so treat it as a likely small edge rather than a guarantee.

Will citrulline give me more reps?
Sometimes. Some 8 gram studies found more reps (Perez-Guisado and Jakeman, 2010; Glenn et al., 2017) and others found none at the same dose (Gonzalez et al., 2018; Chappell et al., 2018). Response appears to be individual.

Works cited

1. Schwedhelm E, Maas R, Freese R, et al. (2008). Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. British Journal of Clinical Pharmacology. PMID 17662090. link
2. Suzuki T, Morita M, Kobayashi Y, Kamimura A (2016). Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men. Journal of the International Society of Sports Nutrition. PMID 26900386. link
3. Glenn JM, Gray M, Wethington LN, et al. (2017). Acute citrulline malate supplementation improves upper and lower body submaximal weightlifting exercise performance in resistance-trained females. European Journal of Nutrition. PMID 26658899. link
4. Perez-Guisado J, Jakeman PM (2010). Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. Journal of Strength and Conditioning Research. PMID 20386132. link
5. Gonzalez AM, Spitz RW, Ghigiarelli JJ, et al. (2018). Acute Effect of Citrulline Malate Supplementation on Upper-Body Resistance Exercise Performance in Recreationally Resistance-Trained Men. Journal of Strength and Conditioning Research. PMID 29210953. link
6. Chappell AJ, Allwood DM, Johns R, et al. (2018). Citrulline malate supplementation does not improve German Volume Training performance or reduce muscle soreness in moderately trained males and females. Journal of the International Society of Sports Nutrition. PMID 30097067. link
7. Theodorou AA, Zinelis PT, Malliou VJ, et al. (2021). Acute L-Citrulline Supplementation Increases Nitric Oxide Bioavailability but Not Inspiratory Muscle Oxygenation and Respiratory Performance. Nutrients. PMID 34684312. link
8. Rhim HC, Kim SJ, Park J, Jang KM (2020). 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. PMID 33308806.