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Creatine Side Effects: What the Evidence Shows and Who Should Avoid It
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Creatine has two reliable side effects: about a kilogram of water weight, and an upset stomach if you take too much at once. Everything else on the usual list of worries, kidney damage, liver damage, hair loss, cramps, dehydration, has been tested and not found in healthy adults at 3 to 5 g a day. The one real complication is that creatine raises creatinine in your blood, which is the marker doctors use to check your kidneys, so it can make a kidney-function test look worse than your kidneys are. That is the main reason doctors are cautious, and it is worth understanding properly.
- Common: 0.8 to 1 kg of water inside muscle; gut discomfort with single doses of 10 g or more
- Not shown in healthy adults: kidney or liver harm, hair loss, cramps, dehydration, dangerous interactions
- The catch: a raised creatinine reading on blood tests, which is a measurement effect, not damage
- Check with a GP first if: you have kidney disease, are pregnant or breastfeeding, are under 18, or take medicines that affect the kidneys
- Daily use: safe at 3 to 5 g for years in the studies that have looked
Why do doctors say no to creatine?
Usually for one of three reasons, and only one of them is about creatine itself. None is about what creatine does in muscle.
The creatinine problem. Your body breaks creatine down into creatinine, which the kidneys clear, and doctors estimate kidney filtration, the eGFR, from blood creatinine: more creatinine, lower estimate.1 Creatine supplementation raises creatinine without changing how the kidneys work, so the estimate drifts down; a 2025 meta-analysis of 12 trials found a small rise in creatinine and no change in measured filtration.2 A GP who sees a borderline eGFR and does not know you take creatine will reasonably worry. Tell them before any blood test.
Caution about the unknown. Many doctors trained before the long-term data existed, and no is the safe default. The data now exists: the International Society of Sports Nutrition's position stand and a 2025 review of the whole literature find no safety signal at recommended doses.3, 4
A genuine reason in your case. If you have reduced kidney function, a condition under treatment, or you are pregnant, a doctor's no is specific advice, not a general view about creatine. Follow it.
Which organ is affected by creatine?
In the sense the question usually means, which organ does it harm, the answer from the evidence is none, in healthy adults.
Kidneys. Across trials from one week to five years, filtration has not changed in healthy kidneys, and in kidney disease the evidence is thin, so ask first;2, 3, 5 the molecule-level explanation, the pooled figures and what to say to your GP are in the creatine vs creatinine guide.
Liver. Liver enzymes have been measured in many creatine trials and have not shown a consistent change.3, 5
What are the actual side effects of creatine?
| Effect | How common | What is going on | What to do |
|---|---|---|---|
| Weight gain of about 1 kg | Most people | Water drawn into muscle cells. Not fat, not puffiness | Nothing. It is part of the mechanism. Details here. |
| Stomach upset, bloating, diarrhoea | Some people, mainly at large single doses | In one trial, 10 g in one go caused diarrhoea in 56% versus 29% for two 5 g doses7 | Keep single doses to 5 g or less, take with food, skip loading |
| Raised blood creatinine | Everyone, slightly | Normal breakdown of the extra creatine2 | Tell your GP before blood tests |
| Muscle cramps or dehydration | Not supported | Studies in athletes training in heat found no increase; some found fewer cramps3, 8 | Drink to thirst as usual |
| Hair loss | Not supported | One 2009 hormone study, never replicated; a 2025 trial by supplier-linked authors found no DHT or hair effect9 | Full evidence here. |
Is creatine safe to take every day?
Yes, at 3 to 5 g. The longest controlled data runs to about five years in athletes, with no adverse effect on health markers, and the position stand concludes that daily use at recommended doses is safe in healthy people.3, 4 How much to take each day is here.
What should you never mix creatine with?
The list is short, and most of it is caution rather than a known reaction.
- Medicines that affect the kidneys. Long-term non-steroidal anti-inflammatory painkillers such as ibuprofen, diuretics ("water tablets") and some blood-pressure medicines. No trial has shown a harmful interaction, but these drugs load the kidneys and creatine adds a variable. Ask your GP or pharmacist first.
- Caffeine. A 2022 systematic review of ten studies found the record inconsistent: a pre-workout caffeine dose does not undo a creatine load, very high daily caffeine through a loading week might blunt it, and both together can upset the stomach.10 Your morning coffee is not a problem.
- Antidepressants. Creatine has been given alongside the SSRI escitalopram in a controlled trial of 52 women at 5 g a day for eight weeks, with no difference in adverse events from placebo.11 Mention creatine to whoever prescribes your antidepressant; the mood trials, and the sleep and vivid-dream reports, are in the creatine and the brain guide.
Who should not take creatine, or should check first?
- Anyone with kidney disease or reduced kidney function. The safety evidence is in healthy kidneys; speak to your specialist.
- Anyone pregnant, trying to conceive or breastfeeding. No randomised trial has given creatine to pregnant women, and no study of any kind covers breastfeeding: a midwife or GP conversation first.14 Creatine while pregnant or breastfeeding has what is known; creatine for women has the life-stage table.
- Anyone under 18. Adolescent reviews report no adverse events and a 2026 systematic review found no short-term signal in kidney, liver or metabolic markers,12, 13 but no trial was designed to test safety and no dose exists for teenagers; the guide to whether creatine is safe for teenagers has the evidence and the GP, school and club route.
- Anyone with a condition under treatment or on regular medication. The answer is usually yes, but it should be your doctor's yes.
- Anyone with high blood pressure or a heart condition. Trials in healthy adults found no consistent change in blood pressure, and the water creatine holds sits inside muscle cells, not the bloodstream;6 nobody with high blood pressure has been studied, so ask first.
- Anyone with bipolar disorder. In one bipolar trial, two of 17 on creatine switched to hypomania or mania; a reason to ask first.15
Sperm, fertility and libido have never been measured in a creatine trial; the creatine for men guide covers them.
Frequently asked questions
What does the NHS say about creatine?
The NHS has no page on creatine as a supplement; its one mention, on the PrEP medicines page, says that taking creatine as a fitness supplement "can affect the results of your kidney function tests" and "If you're using creatine, let your clinic doctor know" (NHS, page last reviewed 10 March 2023).16 Nothing on the NHS site says creatine is unsafe for healthy adults, and nothing endorses it either.
Does creatine cause acne, spots or kidney stones?
No oral creatine trial we found has measured acne, skin or kidney stones; the forum reports have no control group. Anyone who has had a stone asks their GP first.
Can you take creatine if you have diabetes?
Ask the diabetes team first. In one 12-week trial, 25 people with type 2 diabetes on an exercise programme had a lower HbA1c on 5 g (grams) a day than on placebo, with kidney function unchanged on a clearance test;17, 18 one trial in treated patients is a finding, not a reason to take it.
Can you drink alcohol while taking creatine?
No study has tested the two together. There is no known interaction; heavy drinking undoes the training the creatine is there to support.
Can creatine affect your joints, gout or uric acid?
No evidence that it does. The extra water is held in muscle, not joints; joint pain that starts with heavier training is the training. Creatinine and uric acid are different molecules and creatine trials have not reported gout; tell your consultant what you take.
What we don't know
- Safety in existing kidney disease. Small studies only; take medical advice.
- Pregnancy and breastfeeding. No randomised trial in pregnancy and no study in breastfeeding; observational data only.
Sources
- NHS. Chronic kidney disease: diagnosis. https://www.nhs.uk/conditions/kidney-disease/diagnosis/
- Effect of creatine supplementation on kidney function: a systematic review and meta-analysis. BMC Nephrology, 2025. PubMed 41199218.
- Kreider RB, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition, 2017. PubMed 28615996.
- Kreider RB, et al. Creatine supplementation is safe, beneficial throughout the lifespan, and should not be restricted. Frontiers in Nutrition, 2025. PubMed 40331098.
- Antonio J, et al. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition, 2021. PubMed 33557850.
- Powers ME, et al. Creatine supplementation increases total body water without altering fluid distribution. Journal of Athletic Training, 2003. PubMed 12937471.
- Ostojic SM, Ahmetovic Z. Gastrointestinal distress after creatine supplementation in athletes: are side effects dose dependent? Research in Sports Medicine, 2008. PubMed 18373286.
- Jagim AR, et al. Safety of creatine supplementation in active adolescents and youth: a brief review. Frontiers in Nutrition, 2018. PubMed 30547033.
- Does creatine cause hair loss? A 12-week randomized controlled trial. Journal of the International Society of Sports Nutrition, 2025. Randomised trial, 45 men; supplier-linked authors. PubMed 40265319.
- Elosegui S, et al. Interaction between caffeine and creatine when used as concurrent ergogenic supplements: a systematic review. International Journal of Sport Nutrition and Exercise Metabolism, 2022. PubMed 35016154.
- Lyoo IK, et al. A randomized, double-blind placebo-controlled trial of oral creatine monohydrate augmentation for enhanced response to a selective serotonin reuptake inhibitor in women with major depressive disorder. American Journal of Psychiatry, 2012. PubMed 22864465.
- Jagim AR, Kerksick CM. Creatine supplementation in children and adolescents. Nutrients, 2021. PubMed 33670822.
- Rubinchuk A, et al. Evaluating the safety of creatine monohydrate in adolescents: a systematic review of renal, hepatic, and cardiometabolic outcomes. Cureus, 2026. PubMed 42124755.
- Dickinson H, et al. Creatine for women in pregnancy for neuroprotection of the fetus. Cochrane Database of Systematic Reviews, 2014. PubMed 25523279.
- Toniolo RA, et al. A randomized, double-blind, placebo-controlled, proof-of-concept trial of creatine monohydrate as adjunctive treatment for bipolar depression. Journal of Neural Transmission, 2018. PubMed 29177955.
- NHS. Taking PrEP with other medicines and herbal supplements (page last reviewed 10 March 2023; fetched 11 October 2026). https://www.nhs.uk/medicines/pre-exposure-prophylaxis-prep/taking-pre-exposure-prophylaxis-prep-with-other-medicines-and-herbal-supplements/
- Gualano B, et al. Creatine in type 2 diabetes: a randomized, double-blind, placebo-controlled trial. Medicine and Science in Sports and Exercise, 2011. PubMed 20881878.
- Gualano B, et al. Creatine supplementation does not impair kidney function in type 2 diabetic patients: a randomized, double-blind, placebo-controlled, clinical trial. European Journal of Applied Physiology, 2011. PubMed 20976468.
This article is general information, not medical advice. If you have a medical condition or take regular medication, check with your GP or pharmacist before starting creatine.
