Creatine and Warning Signs: When to Get Medical Help

Get urgent help first

• Call 911 (US) for signs of a severe allergic reaction. MedlinePlus says to call 911 if someone is having a serious allergic reaction, and lists swelling of the lips or tongue, throat tightness and trouble swallowing among the signs. [1]
• Poison Help, 1-800-222-1222 (US) if a child, or anyone, has swallowed a large amount of a creatine product or other supplements. For other countries see Poison Help by country.
• Contact a clinician promptly for dark, red or cola-colored urine, much less urine than usual, severe muscle pain or weakness, or flank pain after using creatine, especially with heavy exercise or dehydration. These are signs of muscle breakdown or kidney trouble described below, and many other conditions cause them too.

This page is information only. It does not diagnose anything, and it does not tell anyone to stop or change a prescribed medicine.

How the evidence is labeled

Evidence in adequately nourished people means trials in people with no deficiency. Insufficient evidence means too few studies. Preclinical means animal work. Proper evidence not found means we looked and found nothing usable.

Signs and what the sources say

What research found about common worries

• Weight gain was the only consistently reported side effect in a 2017 position stand (authors with industry ties). [7]
• Single large servings: the soccer trial found diarrhoea more likely after 10 grams taken as one serving than after the same amount split into two. [6] This is a study finding, not advice.
• Cramps and heat: a systematic review found no evidence that creatine hinders heat loss or body fluid balance. [8] Another review found little evidence it adds risk in the heat. [9]
• Kidney tests: a 2026 meta-analysis found creatine raised blood creatinine without change on a direct measure, so a high creatinine result does not by itself mean damage. [10] Tell your provider you use creatine before testing. [11]

Allergy and overdose: what we could not find

Proper evidence not found for creatine allergy: we searched PubMed for creatine with allergy, anaphylaxis and hypersensitivity and found nothing usable. A reaction could come from another ingredient in a product, which we cannot tell from these sources. Proper evidence not found for a defined toxic amount of creatine. Call Poison Help if in doubt.

Early kidney disease can be silent

The NHS says kidney disease does not tend to cause symptoms at an early stage, and is often found by routine blood or urine tests. [3] That is one reason people with kidney conditions should ask a clinician before starting creatine. [7] [12]

Extra caution

• Kidney or liver disease, regular medicines: see creatine and kidney disease and medicines.
• Pregnancy and breastfeeding: randomized trials of safety in human pregnancy are not available. [13] See creatine in pregnancy and breastfeeding.
• Teens: see creatine for teens.
• Before surgery: the sources we read did not address creatine specifically; tell your surgical team about every supplement. See supplements before surgery.
• Case reports are single cases and cannot show cause. One man with muscle breakdown had done a resistance session of over 4 hours and used several supplements, and his clinicians advise asking about supplement use in muscle injury. [14] Another case, in a 16-year-old, involved severe autoimmune hypothyroidism, extreme dieting and dehydration alongside creatine. [15]

For product problems see quality testing and the long-term safety page.