Does L-Citrulline Break a Fast? What Science Says

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If you work out fasted (meaning you don’t eat anything before a workout), you might wonder if you can include L-citrulline during your fasting hours without counting it as “breaking the fast.” As a Dietitian, I’m here to explain the dos and don’ts.

Key Takeaways

  • L-citrulline on its own won’t affect insulin response, meaning it won’t break your fast. However, consuming L-citrulline with a pre-workout supplement may break a fast if it contains sweeteners or additional calories.
  • Avoid taking L-citrulline with calorie-based drinks such as milk, protein shakes, or fruit juice to prevent it from breaking your fast.  You can also take L-citrulline in pill form with water to avoid breaking your fast.
  • L-citrulline works best when taken 30 minutes before a workout. If you work out in the afternoon or evening, you may want to take it during feeding hours so your body can use it properly during training.

Will L-Citruline Break Your Fast?

An L-citrulline supplement with no added sugars or one you dissolve in a non-caloric beverage should not break your fast.

It is safe to consume during fasting hours because it doesn’t affect your insulin response (when the pancreas releases the hormone insulin to help manage carb-containing foods). 

Make sure to read the nutritional label for your L-citrulline content since some additives (like sugars or non-caloric sweeteners) can break your fast. Such is the case when you take L-citrulline in a pre-workout supplement. 

A pure L-citrulline supplement, such as the one from BulkSupplements, has only one ingredient: L-citrulline. It doesn’t contain added sugars, flavors, or other ingredients that might affect fasting. 

Bulk Supplements L-Citrulline

So, taking this supplement with water or other non-caloric beverages (like black coffee or unsweetened tea without milk) won’t affect your insulin response. However, taking it with fruit juice or a sugar-containing electrolyte will break your fast. 

Furthermore, an L-citrulline supplement like the one from Nutricost contains additives such as beetroot powder and sucralose (an artificial, non-caloric sweetener), which can impact insulin response.

There is some controversy regarding the use of non-caloric sweeteners.

While some studies say that artificial sweeteners have no impact on insulin response, others say they can affect glucose and insulin response. 

If you decide to have L-citrulline while fasting, don’t mix it with a beverage with calories, like fruit juice, a protein shake, or any high-carb option.

Also, it’s best to avoid beverages with non-caloric sweeteners since they might affect insulin response. 

Is It Safe to Take L-Citrulline on an Empty Stomach?


Yes, it is safe to take L-citrulline on an empty stomach. It might even have better absorption than when you take it with food. 

However, this comes down to individual preference.

While it is not common to get gastric discomfort when taking L-citrulline, some people that are sensitive to it might experience stomach cramps, bloating, gas, and diarrhea. 

If you are one of those people, you may want to wait until your feeding window to take L-citrulline with a small meal or snack, such as a protein shake with some fruit or a piece of toast with peanut butter. 

While it won’t absorb as well, you will still get the benefits of it, such as increased blood flow to deliver more nutrients and oxygen to muscles.

Should You Take L-Citrulline When Fasting or During a Feeding Window?

Whether you take L-citrulline when fasting or during your feeding hours depends on personal preference, when you work out, and how you react to it.

You should take L-citrulline 30-40 minutes before a workout to help increase blood flow to deliver more nutrients and oxygen to your muscles.

You should also take it on an empty stomach for better absorption. Depending on when you work out, this may or may not fall during your fasting period.

For example, if you have fasting hours from 7 pm to 11 am and work out at 8 am, you should take L-citrulline at 7:30 am (during fasting hours).

However, if you work out in the afternoon, consuming L-citrulline during your feeding window is better. Take it on an empty stomach (2 hours before or after a meal) for the best results. 

As mentioned before, a very small percentage of people might get stomach problems from taking L-citrulline on an empty stomach. 

If that is the case, you might want to take the supplement 60-90 minutes after a meal.

That way, you don’t have it with food (which could affect its absorption), but your stomach won’t be completely empty. 

How to Take L-Citrulline Without Breaking a Fast

To avoid breaking your fast when you take L-citrulline, add the powder to water or take it in capsule form. Avoid taking it with caloric beverages or beverages containing non-caloric sweeteners to prevent an insulin response.

On top of that, choose unflavored L-citrulline supplements without any other additives. In other words, make sure it is pure L-citrulline. 

Here are some of my favorite pure L-citrulline options that won’t break your fast. 

Keep in mind that the recommended dosage for L-citrulline is 6,000 to 8,000 mg

Jacked Factory L-Citrulline Fermented Powder Supplement

Jacked Factory L-Citrulline supplement is an excellent way to boost your citrulline intake.

One scoop provides 2,000 mg. So, to help reach the recommended dosage, you can break it down into three doses throughout the day to avoid any stomach problems. 

The only ingredient is L-citrulline, which won’t cause any problems with your fasting. 

Type-Zero L-Citrulline

If you don’t like to take capsules, you can take L-citrulline in powdered form. A great option besides the BulkSupplements one mentioned above is Type Zero L-Citrulline since it only contains citrulline.

Additionally, one thing I like about this supplement is that it provides 6,000 mg, which is a very good dosage for L-citrulline to improve sports performance. 

What Other Supplements Can Break a Fast?


Ahmad SY, Friel JK, Mackay DS. Effect of sucralose and aspartame on glucose metabolism and gut hormones. Nutr Rev. 2020 Sep 1;78(9):725-746. doi: 10.1093/nutrit/nuz099. PMID: 32065635.

Méndez-García LA, Bueno-Hernández N, Cid-Soto MA, De León KL, Mendoza-Martínez VM, Espinosa-Flores AJ, Carrero-Aguirre M, Esquivel-Velázquez M, León-Hernández M, Viurcos-Sanabria R, Ruíz-Barranco A, Cota-Arce JM, Álvarez-Lee A, De León-Nava MA, Meléndez G, Escobedo G. Ten-Week Sucralose Consumption Induces Gut Dysbiosis and Altered Glucose and Insulin Levels in Healthy Young Adults. Microorganisms. 2022 Feb 14;10(2):434. doi: 10.3390/microorganisms10020434. PMID: 35208888; PMCID: PMC8880058.

Gonzalez AM, Trexler ET. Effects of Citrulline Supplementation on Exercise Performance in Humans: A Review of the Current Literature. J Strength Cond Res. 2020 May;34(5):1480-1495. doi: 10.1519/JSC.0000000000003426. PMID: 31977835.

About The Author

Brenda Peralta

Brenda Peralta is a Registered Dietitian and certified sports nutritionist.  In addition to being an author for, she fact checks the hundreds of articles published across the website to ensure accuracy and consistency of information.

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