L Citrulline and Citrulline Malate: Pump, Endurance, Dosage and Evidence

Citrulline may slightly improve high repetition training and soreness. The usual dose is 6 to 8 grams of citrulline malate, taken 30 to 60 minutes before training.

What is citrulline?

Citrulline is an amino acid that was first isolated from watermelon, whose Latin genus name is Citrullus. That is where the name comes from. It is not used to build muscle protein. Instead, it plays a role in a cycle in your body that clears ammonia, and it is turned into another amino acid called arginine, which in turn is used to make nitric oxide.

Nitric oxide relaxes and widens blood vessels, which increases blood flow to working muscles. More blood flow means more oxygen and nutrients delivered and faster removal of waste products. This is the idea behind the "pump" that lifters talk about, and it is why citrulline is a common ingredient in pre workout supplements.

Why citrulline instead of arginine?

If arginine is the source of nitric oxide, why not take arginine directly? Because most oral arginine is broken down in the gut and liver before it reaches the bloodstream. Citrulline bypasses this problem. It is absorbed intact, travels to the kidneys and is converted into arginine there. Studies have shown that taking citrulline raises blood arginine levels more effectively than taking arginine itself. That is why most modern products use citrulline.

L citrulline vs citrulline malate

You will see two forms on labels.

• L citrulline is pure citrulline.
• Citrulline malate is citrulline bonded to malic acid, a compound involved in energy production. The common ratio is 2:1, meaning two parts citrulline to one part malate.

Because of that ratio, 8 grams of citrulline malate contains only about 5 to 5.5 grams of actual citrulline. So the doses are not interchangeable, and the label must tell you which you are buying.

What does the research say?

Citrulline is one of the more promising pre workout ingredients, though the evidence is more modest than the marketing suggests.

Strength and high repetition work. One small and often cited study reported that people taking 8 grams of citrulline malate completed many more repetitions in a bench press session and had less soreness in the following days. Later studies have been less dramatic. A systematic review and meta analysis by Trexler and colleagues that pooled many trials found small improvements in performance, mainly in sets taken close to failure with higher repetitions. The effect is real but small.

Endurance. Some studies in cyclists and runners suggest that citrulline can improve oxygen use and time to exhaustion, while others found no difference. The evidence is mixed.

Muscle soreness. A few studies show reduced soreness in the days after hard training. This is promising but not consistent.

Blood pressure and circulation. Citrulline appears to improve blood vessel function, and some research shows a mild blood pressure lowering effect, especially in people with raised blood pressure. This is part of why you should speak to a doctor if you are on blood pressure medication.

In short, citrulline is not magic, and it will not replace training, food or sleep. For many people it feels like a better pump and slightly better endurance in the last few sets.

How much citrulline should you take?

• Citrulline malate: 6 to 8 grams, taken 30 to 60 minutes before exercise.
• L citrulline: 3 to 6 grams, taken 30 to 60 minutes before exercise.

Some studies use a daily dose for a week or more, which may lift baseline levels, but a single dose before training is the most common and best supported use. Start at the lower end to see how you feel. Some studies have tested doses up to about 15 grams of citrulline without problems in healthy people, but there is no good reason to take more than you need.

Can you get enough citrulline from watermelon?

Watermelon does contain citrulline, mostly in the white rind just beneath the red flesh. But the amount in a normal serving is far smaller than what is used in studies, so you would need to eat a very large quantity to match a supplement dose. Watermelon is still a great hydrating snack, particularly in hot weather. For more on hydration, see why hydration affects your performance.

Is citrulline safe?

At normal doses, citrulline is considered safe for healthy adults, and side effects are uncommon. Some people feel mild stomach discomfort or nausea, usually from taking a large dose on an empty stomach. Unlike arginine, citrulline rarely causes digestive problems. Take it with a small snack if you are sensitive.

Speak with your doctor before using citrulline if you:

1. Take medicine for blood pressure.
2. Take medicine for erectile dysfunction or nitrates for heart conditions.
3. Are pregnant or breastfeeding.
4. Have kidney or liver disease.

How to combine citrulline with other pre workout ingredients

Citrulline pairs well with other ingredients that have evidence behind them.

• Caffeine improves alertness and perceived effort. Read caffeine as a performance supplement.
• Creatine supports strength and short power efforts. See creatine dosage, loading and safety.
• Beta alanine helps efforts lasting one to four minutes. See beta alanine dosage, tingling and benefits.
• Carbohydrates in a pre workout meal provide the fuel that powers the session.

Be careful with all in one products. They often underdose the useful ingredients, such as 1 to 3 grams of citrulline instead of the 6 to 8 grams that studies used, and then hide the amounts inside a "proprietary blend". For a detailed look at what is in them, read pre workout supplements: what is actually in them.

What to eat before training

Supplements work best on top of a good meal. A few hours before training, aim for carbohydrates, some protein and little fat, for example rice with chicken or oats with fruit. This baked brown rice with shrimp and zucchini is a simple, carb rich pre workout meal with about 40 grams of protein. See also what to eat before a workout.

Who might benefit most?

1. Lifters who train close to failure with sets of 8 to 15 repetitions or more.
2. People who like the sensation of a better pump and feel it helps their motivation.
3. Athletes doing repeated high intensity work, such as circuits.
4. Those who often train in the evening and want something that is not heavy on the stomach.

If you are a beginner, spend your money first on protein foods, a calorie target that matches your goal and consistent training. Our guide to the best supplements for beginners in the gym puts them in order.

Tips to get the best from citrulline

1. Use it consistently for at least a week before judging it.
2. Take it with a glass of water.
3. Do not exceed the doses used in studies.
4. Choose a single ingredient product so you know the exact dose.
5. Pick a brand that uses independent testing. See understanding supplement quality and third party testing.
6. Do not rely on it to fix poor sleep or low food intake.

Frequently asked questions

Does citrulline help build muscle? Not directly. It may help you do slightly more work in training, which can support growth over time.

Is citrulline better than arginine? For raising blood arginine levels, yes. Citrulline is absorbed better.

Can I take citrulline every day? Yes, studies have used daily dosing. Cycling is not required.

Can women take citrulline? Yes. There is no reason for women to avoid it.

Does citrulline break a fast? Yes. It is an amino acid with calories and may end a strict fast.

This article is general information and not medical advice. If you have a medical condition or take medication, talk to your doctor before using supplements.

How FiTPLATE helps you fuel your training

A pump is nice. Fuel and recovery do the real work.

• Pre and post workout meals made easy. Browse recipes tagged for before and after training in the Sports Kitchen, each showing calories, protein, carbs and fat.
• Meals from what you have. Take a photo of your fridge, set a target, and FiTPLATE builds a meal for it.
• A daily log that includes supplements. Search, scan or quick add so you can see the whole day.
• A plan that adapts. FiTPLATE sets your calories from your goal and reviews your progress weekly.

Start your free trial and plan your training meals

References

• Trexler ET et al. Acute effects of citrulline supplementation on high intensity strength and power performance: a systematic review and meta analysis. Sports Medicine, 2019.
• Schwedhelm E et al. Pharmacokinetic and pharmacodynamic properties of oral L citrulline and L arginine: impact on nitric oxide metabolism. British Journal of Clinical Pharmacology, 2008.
• Pérez Guisado J, Jakeman PM. Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. Journal of Strength and Conditioning Research, 2010.