Short answer
Plain creatine probably doesn’t break a fast if your goal is calories or insulin. A plain creatine monohydrate label lists no calories, which under FDA rules means fewer than 5 per serving, and a 1996 study found creatine alone did not raise insulin. If your goal is autophagy, nobody knows: we found no human study of creatine and autophagy.
Calories
Under FDA labeling rules, a supplement must list calories on its Supplement Facts panel once it has more than an amount that can be declared as zero, and fewer than 5 calories may be expressed as zero. A plain creatine monohydrate powder on file in the NIH Dietary Supplement Label Database lists a single ingredient, 5 g of creatine monohydrate, and no calories line. Flavored powders, gummies and creatine stirred into juice are another matter. If the label shows a calories line, the product has 5 or more per serving.
Insulin
In a 1996 study in the American Journal of Physiology, 24 men took 5 g of creatine dissolved in liquid four times a day for 5 days. Creatine alone had no effect on blood insulin; when it was followed by 93 g of simple sugar, insulin rose sharply. What you mix it with matters more.
A 2003 study in vegetarians taking 5 g a day for 42 days found no change in the insulin response to a glucose drink, with a trend toward higher fasting glucose that did not reach significance. A 2022 meta-analysis of 9 studies found no significant effect on fasting glucose or insulin resistance.
What nobody has tested
The key insulin study is from 1996 and included only 24 men, and none of these studies was designed around fasting. We found no human study on whether creatine affects autophagy, the cell-recycling process some people fast for, so any claim either way is a guess. Creatine is a compound your body already makes from the amino acids arginine, glycine and methionine. If your fast is for a medical reason, such as before surgery or a blood test, follow the instructions you were given and ask that clinician.
Related questions
Should I skip creatine before a fasting blood test?
Ask whoever ordered the test. Creatine raises creatinine, a kidney marker, so some clinicians prefer a pause and others just note that you take it; see our page on creatine and kidneys.
Do creatine gummies break a fast?
Check the Supplement Facts panel. If it lists calories or sugars, the gummy adds them; plain powder in water does not.
Read next
Sources
- Green et al., Am J Physiol: carbohydrate, creatine and insulin (1996)
- Rooney et al., Ann Nutr Metab: creatine, glucose and insulin secretion (2003)
- Delpino & Figueiredo, Clin Nutr ESPEN: creatine and glycemic control meta-analysis (2022)
- 21 CFR 101.36: nutrition labeling of dietary supplements
- NIH Dietary Supplement Label Database: creatine monohydrate label (entered Aug 2025)
Published 2026-10-07 · Last checked 2026-10-07
Educational content, not medical advice. Made for the United States.