Creatine is one of the most studied supplements there is, and also one of the most rumoured about. Hair loss, kidney damage, dehydration and bloating all come up in search results. This guide goes through each one against the controlled trials, then covers dose and who should be careful. For what creatine is and what it does for memory, see our creatine guide.
The Short Version
| Concern | What the evidence shows |
|---|---|
| Hair loss | A 2025 12-week trial found no change in DHT or hair measures; the original worry came from one 2009 study |
| Kidney damage | No change in kidney function in healthy people; creatinine on blood tests rises |
| Bloating and weight gain | Real: a small rise, attributed mainly to muscle with some water |
| Stomach upset | Real at high doses; dose-dependent |
| Dehydration and cramps | Largely unsupported by controlled studies |
| Cancer | No link found in available research |
Does Creatine Cause Hair Loss?
Probably not. The worry traces back to a 2009 study of 20 college rugby players, in which 7 days of 25g-a-day loading raised DHT, a hormone linked to male-pattern baldness, by 56%. Hair loss itself wasn't measured, and nobody had directly tested it until recently Preliminary.
In 2025, a randomized trial did. Forty-five resistance-trained men aged 18–40 took 5g of creatine a day or a placebo for 12 weeks; 38 finished. The researchers measured total and free testosterone, DHT and the DHT-to-testosterone ratio, and checked hair follicle health with a trichogram and a hair-density imaging system. There were no differences between the creatine and placebo groups in DHT, the DHT ratio or any hair measure Preliminary. The authors described it as strong evidence against the claim.
The limits: it's one trial in young men, it used 5g a day without a loading phase, and 12 weeks is short for hair changes. If you have a family history of hair loss and want the most cautious route, skipping loading and staying at 3–5g a day matches what the trial tested.
Is Creatine Bad for Your Kidneys?
Not in healthy people, according to the trials. A 12-week randomized, double-blind trial gave resistance-trained people on a high-protein diet 20g a day for 5 days and then 5g a day. Kidney filtration, measured directly with a tracer, didn't differ from placebo, and creatinine clearance, urea, electrolytes and protein in the urine were unchanged Established. In a double-blind trial of 175 people with ALS taking 10g a day for an average of about 310 days, blood urea and the rate of protein in the urine didn't rise. A 2019 meta-analysis also found no kidney damage at the amounts and durations studied.
The catch is that creatine breaks down into creatinine, the marker doctors use to check kidney function, so a blood test can look worse even when your kidneys are fine. Tell your doctor you take creatine before kidney tests. Reviews advise caution for people with existing kidney disease, because that group has been studied far less.
Water Weight and Bloating
Many people gain a little weight in the first weeks. A review of the research found body mass rises of about 1.0–2.3%, attributed to fat-free mass, mainly muscle, though water retention probably contributes. In the long ALS trial, swollen limbs were seen more often on creatine after two months, probably from water retention. If the number on the scale matters to you, expect a small early rise, which a review attributed mainly to muscle, not fat.
Stomach Upset and Diarrhea
Gastrointestinal effects are dose-dependent and not universal. In the ALS trial at 10g a day, nausea (23% vs 24%), stomach discomfort (19% vs 18%) and diarrhea (35% vs 24%) were similar to or only slightly higher than on placebo, and three people on creatine stopped because of severe diarrhoea or nausea. Large single doses and loading phases are where upset is most likely, so splitting the dose, taking it with food or skipping loading usually helps.
Dehydration and Muscle Cramps
This is a common claim that controlled studies don't support. A 2025 review concluded claims that creatine causes dehydration or cramps during exercise are largely unsupported, with no significant effects on hydration or temperature regulation, and that creatine may even reduce cramps. Drink normally; you don't need extra water because of creatine.
Cancer, Purity, and Long-Term Safety
- Cancer: the same review found that although theoretical concerns about creatine forming carcinogenic compounds have been discussed, the research doesn't support a link with cancer.
- Purity: one review concluded the main health risk is probably the purity of commercial products, so buy creatine monohydrate from a brand that publishes third-party testing.
- Long term: the ISSN position stand reports that short- and long-term supplementation, up to 30g a day for 5 years, was safe and well tolerated in healthy people. That is a position stand, and 30g a day is far more than anyone needs.
How Much Creatine to Take
| Approach | Dose |
|---|---|
| Everyday use | 3–5g a day of creatine monohydrate (about 0.1g per kg of body weight) |
| Used in the hair-loss trial | 5g a day for 12 weeks, no loading |
| Used in the kidney trial | 20g a day for 5 days, then 5g a day for 12 weeks |
| Loading (optional) | 20–25g a day for about a week, which is when stomach upset is most likely |
Loading fills muscle stores faster but isn't required; 3–5g a day gets there over a few weeks. Take it any time of day, consistently.
Who Should Be Careful
- Kidney disease or reduced kidney function: ask your doctor first, because trials in healthy people don't cover this.
- Pregnancy and breastfeeding: a 2025 review notes evidence is lacking, so check with your doctor or midwife.
- Medication affecting the kidneys: tell your doctor or pharmacist you take creatine.
- Under 18: speak to a doctor first.
If you drink coffee, see our creatine guide on creatine and caffeine.
