Who Should Not Take Creatine Monohydrate
Creatine monohydrate is the most thoroughly researched sports supplement on the market, and for most healthy adults it has an excellent safety record. Even so, "safe for most" is not the same as "safe for all". Our editors gathered the situations in which creatine should be avoided, postponed or discussed with a doctor first.
Why creatine is considered safe for most people
Creatine is produced naturally in the liver, kidneys and pancreas from the amino acids arginine, glycine and methionine, and it is also obtained from meat and fish. Around 95% of the body's creatine is stored in skeletal muscle, where it helps regenerate ATP during short, intense efforts.
Supplementation raises muscle creatine stores, which explains its well-documented benefits for repeated sprints, strength and lean mass gains when combined with training. In Great Britain, an authorised health claim states that daily intake of 3 g of creatine can increase physical performance in successive bursts of short-term, high-intensity exercise.
The International Society of Sports Nutrition position stand by Kreider and colleagues reviewed hundreds of studies and concluded that short- and long-term supplementation at recommended doses is safe and well tolerated in healthy people. A later review by Antonio and co-authors addressed common myths, including hair loss and dehydration, and found little support for them.
The cases below are therefore not about creatine being "dangerous" in general, but about specific situations where the balance of risks and unknowns changes.
Kidney disease and kidney risk factors
The best-known concern is the kidneys. Studies in healthy athletes, such as the one by Poortmans and Francaux, found no deterioration in kidney function with long-term creatine use, and a meta-analysis by de Souza e Silva and colleagues reached a similar conclusion for people without kidney disease.
People with existing chronic kidney disease (CKD), a single kidney or reduced kidney function are a different matter. There are isolated case reports, including one published in The Lancet by Pritchard and Kalra, describing deterioration of renal function in a patient with pre-existing kidney disease who took creatine. Data in CKD are simply too limited to call it safe.
Caution is also sensible for people with diabetes or high blood pressure that has already affected the kidneys, and for anyone regularly taking drugs that can strain the kidneys, such as high-dose non-steroidal anti-inflammatories.
An important practical point concerns blood tests. Creatine is converted to creatinine, the marker used to estimate kidney function (eGFR). Supplementation can raise serum creatinine slightly without real kidney damage, so tell your doctor you are taking it before routine blood work. A cystatin C test may help clarify the result.
Groups who should avoid or delay creatine
Several groups lack enough safety data for routine use. In these cases, the default position is to avoid creatine unless a doctor recommends it for a specific reason.
Pregnancy and breastfeeding are the clearest example. There is growing scientific interest in creatine for maternal and foetal health, but this is still research territory and not grounds for self-supplementation.
For under-18s, professional bodies generally advise that young athletes focus on training, diet and sleep. Some paediatric clinical studies have used creatine safely, but supplement use in adolescent sport is best decided with a doctor or registered sports dietitian.
Some psychiatric case reports have described manic episodes in people with bipolar disorder who started creatine, and it may interact with mood-stabilising treatment. People with bipolar disorder should discuss it with their psychiatrist first.
| Situation | Recommendation | Reason |
|---|---|---|
| Chronic kidney disease or single kidney | Avoid unless specifically advised | Insufficient safety data, case reports |
| Pregnancy or breastfeeding | Avoid self-supplementation | Lack of safety data |
| Under 18 | Only with professional guidance | Limited data, priorities elsewhere |
| Bipolar disorder | Discuss with psychiatrist | Case reports of mania |
| Taking nephrotoxic drugs or diuretics | Discuss with GP | Combined kidney strain |
| Upcoming kidney blood tests | Inform the doctor | Creatinine may rise artificially |
Side effects and practical precautions
For those without contraindications, side effects are usually minor. The most common is a gain of 1–2 kg of body weight in the first weeks, mostly water stored inside muscle cells. For weight-category athletes this matters, so timing should be planned around competition.
Digestive discomfort, bloating or diarrhoea can occur, mainly with large single doses during a "loading phase". A steady intake of 3–5 g per day avoids loading altogether and reaches full muscle saturation within roughly three to four weeks.
Quality matters too. Choose plain creatine monohydrate, ideally from products with third-party batch testing if you are a tested athlete, to reduce the risk of contamination with prohibited substances.
Practical precautions worth following include:
- drink enough fluid during the day, especially in hot conditions;
- avoid combining creatine with high-dose stimulants in "all-in-one" products;
- stop and seek advice if you notice swelling, reduced urine output or unusual muscle pain;
- tell any doctor ordering blood tests that you take creatine.
Editorial conclusions
Creatine monohydrate is among the safest and most effective supplements available for healthy adults. That reputation is deserved, but it rests on studies in people without significant illness.
People with kidney disease, pregnant or breastfeeding women, adolescents and people with bipolar disorder fall into the groups where creatine should not be self-prescribed. Anyone taking medicines that affect the kidneys should check first.
The creatinine blood test issue is one of the most common practical problems: an "abnormal" result may reflect the supplement rather than kidney damage, so always mention it.
For more on this subject, see our articles on creatine loading versus daily dosing, on understanding eGFR and creatinine results, and on choosing batch-tested supplements.
References
- Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr. 2017;14:18.
- Antonio J, Candow DG, Forbes SC, et al. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show? J Int Soc Sports Nutr. 2021;18(1):13.
- Poortmans JR, Francaux M. Long-term oral creatine supplementation does not impair renal function in healthy athletes. Med Sci Sports Exerc. 1999;31(8):1108–1110.
- Pritchard NR, Kalra PA. Renal dysfunction accompanying oral creatine supplements. Lancet. 1998;351(9111):1252–1253.
- de Souza e Silva A, Pertille A, Reis Barbosa CG, et al. Effect of creatine supplementation on renal function: a systematic review and meta-analysis. J Ren Nutr. 2019;29(6):480–489.
- Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
