Creatine Side Effects: What’s Real, What’s Myth

Creatine side effects are mostly mild for healthy adults. At the usual 3 to 5 grams a day, the only ones that show up consistently in research are a few pounds of water weight in the first weeks and, at large single doses, an upset stomach. The big fears, such as kidney damage, dehydration, cramps and hair loss, have not held up in controlled studies of healthy people.

That doesn’t mean creatine is right for everyone. People with kidney disease, pregnant women and people with bipolar disorder have good reasons to check with a doctor first. Below, we grade each claim by the strength of the evidence and show who paid for the research.

Is creatine safe? What the big reviews say

Creatine is a compound your body makes from amino acids and also gets from red meat and seafood. It is one of the most studied sports supplements, and two reviews from the International Society of Sports Nutrition (ISSN) sum up its safety:

• The 2017 ISSN position stand says the only side effect consistently reported in the research is weight gain. It concludes that doses up to 30 grams a day, for as long as five years, have been safe and well tolerated in healthy people and in a range of patient groups.
• A 2021 ISSN review of common myths concluded that, at recommended doses, creatine does not cause kidney damage in healthy people or cause dehydration and cramps, and that the evidence does not show it causes hair loss.

Independent reviewers broadly agree. Scientists at Germany’s Federal Institute for Risk Assessment reported that several regulatory authorities have judged 3 grams a day unlikely to pose safety concerns for healthy adults, although those judgments left out pregnant and breastfeeding women. The NIH Office of Dietary Supplements says studies have found no consistent set of side effects other than weight gain. It calls creatine safe for healthy adults in the short term and says evidence supports several years of use.

Who pays for creatine research?

You should know who is talking. The 2017 position stand was prepared with support from the Council for Responsible Nutrition, a supplement-industry trade association, and its lead author disclosed industry grants for creatine research and consulting work. Most authors of the 2021 review disclosed ties to creatine sellers, and several sit on the scientific advisory board of AlzChem, a company that makes creatine. That doesn’t make their conclusions wrong, but it is why we also lean on work from other groups, such as a 2026 kidney meta-analysis by university researchers in Greece and a 2020 meta-analysis in women whose authors declared no conflicts.

Creatine side effects at a glance

Does creatine damage your kidneys?

In healthy people, the best evidence says no. A 2026 meta-analysis pooled 20 randomized studies. Creatine raised blood creatinine by an average of 0.13 mg/dL (about 11 µmol/L), but there was no significant difference in urea or in eGFR, the standard estimate of how well your kidneys filter. The authors noted that trials lasting longer than a year are still needed. Older studies of athletes who had taken creatine for 10 months to 5 years also found normal kidney filtration.

The kidney scare largely traces back to a 1998 case report. The patient was a young man who had already had kidney disease for years and was taking cyclosporine, a drug known to be hard on the kidneys. Later case reports were clouded by medicines, existing kidney disease, other supplements, huge doses or steroids.

Why creatine can make a kidney blood test look worse

Your muscles constantly break creatine down into creatinine, which healthy kidneys filter out. Doctors use blood creatinine as a stand-in for kidney function. Take more creatine and you make more creatinine, so the number can rise even when your kidneys are fine. Eating lots of meat can do the same.

A 2010 case report shows the trap. A 20-year-old man with only one kidney took 20 grams of creatine a day for 5 days, then 5 grams a day for a month. His blood creatinine rose from 1.03 to 1.27 mg/dL (91 to 112 µmol/L), and his creatinine-based estimate of kidney function fell from 88 to 71. But his kidney filtration, measured directly with a gold-standard tracer test, didn’t change: 81.6 before and 82.0 after. One case proves little on its own, but it shows how a creatinine result can falsely suggest kidney damage.

So tell your doctor you take creatine before any blood work. If a result looks off, markers that don’t depend on creatine, such as cystatin C or albumin in the urine, give a clearer picture.

Who needs to be careful

The gap in the research is people who already have kidney problems. A 2023 review from a Brazilian research group that has run several of the kidney trials says the evidence in existing kidney disease is very limited, and advises that people with very low kidney function should avoid creatine. It also suggests checking kidney function now and then in higher-risk people, such as some older adults, who take creatine long term. One of its authors has received research grants and creatine donations from AlzChem and sits on its scientific advisory board. If you also eat a high-protein diet, our review of high-protein diets and kidney health covers that question.

Does creatine cause bloating, water retention or weight gain?

Yes, at first, and this is the most common real side effect. Creatine draws water into your muscles along with it. According to the NIH, several studies found that creatine taken during a strength-training program added about 2 to 4 pounds (1 to 2 kg) of body weight in a month. A loading phase of 20 grams a day for 5 to 7 days typically adds about 2 to 7 pounds (1 to 3 kg), mostly water. Early studies measured roughly 2 to 4 cups (0.5 to 1 liter) of extra fluid.

• It’s mostly inside the muscle. Researchers attribute the early gain mainly to extra water inside muscle cells. Several 5- to 10-week training studies found no rise in total body water, and in one that did, the extra water kept pace with the extra muscle.
• It isn’t fat. Randomized trials lasting from one week to two years have not found that creatine increases fat mass.
• Results in women are reassuring. A 2020 meta-analysis of studies in women found no significant weight gain compared with placebo. Read more in our guide to creatine for women over 40.

If scale weight matters, say in a weight-class or endurance sport, skip the loading phase; the NIH notes the extra weight may hold back endurance performance. For a look at what the first month can feel like, watch our video on taking creatine for 30 days.

Can creatine upset your stomach?

It can, mostly when you take a lot at once. In a 2008 trial, 59 top-level male soccer players took either two 5-gram doses a day, one 10-gram dose, or a placebo for 28 days. Diarrhea was reported by 56% of the single 10-gram group, against 29% of the split-dose group and 35% of the placebo group. The split dose was no worse than the placebo. The trial’s PubMed record lists no funding or conflict statement.

A third of the placebo group also reported diarrhea, so some stomach trouble blamed on creatine may have other causes. If you load, the 2021 ISSN review advises splitting the 20 grams into smaller servings, because servings over 10 grams may cause diarrhea.

Does creatine cause dehydration or muscle cramps?

The controlled evidence says no. The worry made sense on paper: if creatine pulls water into muscle, maybe less is left to cool you down. In the early 2000s, the American College of Sports Medicine even advised people exercising intensely or in hot weather to avoid it.

Then the trials came in. A 2009 systematic review with meta-analyses of 10 controlled trials on creatine and heat or hydration found no evidence that creatine hampers your body’s ability to shed heat or upsets fluid balance, and athletes exercising in the heat had no adverse effects at recommended doses.

The cramp reports mostly come from surveys in which athletes rate their own symptoms. These didn’t account for other supplements or doses, and in one, 91% of users took more than the recommended maintenance dose. A study in college football players found that creatine users actually had fewer cramps, but the players chose whether to take it, so that result is weak evidence.

Creatine hasn’t been shown to dehydrate you, but staying hydrated still matters when you train hard or in hot weather. Use our free water intake calculator to get a daily target for your weight, activity and climate.

Hair loss, liver and mood: the less common worries

Hair loss. This fear comes from a single 2009 study in 20 rugby players, where the hormone DHT rose by 56% after a week of creatine loading. Hair was never measured, and the result hasn’t been repeated. In a 2025 trial, 38 men who completed 12 weeks of 5 grams a day or a placebo showed no difference in DHT or in hair density, follicle counts or thickness. Several of its authors disclosed advisory or consulting roles with supplement and creatine brands. We cover the details in does creatine cause hair loss?

Liver. In a 21-month study of college football players taking 5 to 10 grams a day, liver enzymes didn’t differ in any clinically important way between creatine users and non-users. The 2020 meta-analysis in women, covering 29 studies and 951 participants, found no difference in liver or kidney function and no serious adverse events.

Mood and bipolar disorder. The evidence is thin but worth knowing. In a 2018 trial of 35 adults with bipolar depression, 2 of the 17 people given 6 grams of creatine a day switched into hypomania or mania early in the trial. The authors declared no conflicts. Numbers this small can’t prove creatine caused it, but if you have bipolar disorder, talk to your psychiatrist first. We searched PubMed and found no controlled human study showing that creatine causes anxiety. For what it may do for the brain, see our review of creatine and cognition.

Who should not take creatine?

Creatine is low risk for most healthy adults, but talk to your doctor first if any of these apply:

• You have kidney disease or reduced kidney function. This is the group with the least research.
• You are pregnant or breastfeeding. Research on creatine in pregnancy has so far been mostly in animals, and regulators’ safety judgments left you out.
• You have bipolar disorder, because of the reports of mania above.
• You take medicines that can affect the kidneys. The 1998 case involved cyclosporine. Your pharmacist can check your list.
• You are under 18. The ISSN review says creatine appears safe for teens but calls the evidence limited.

If you’re over 50, creatine can be a useful partner to strength training and protein, as we explain in creatine and protein for aging. Ask your doctor whether an occasional kidney check makes sense, and watch our short video on creatine mistakes after 50.

How to take creatine with the fewest side effects

1. Choose creatine monohydrate. It is the most studied form. The NIH says other forms haven’t been proven better for raising muscle creatine, digestibility, stability or safety, and German risk assessors found limited safety data on many of them.
2. Take 3 to 5 grams a day and skip loading. In a classic study, 3 grams a day for 28 days raised muscle creatine as much as 20 grams a day for 6 days. Same result, just slower, with less water weight. Watch our video on what 5 grams a day does.
3. Keep each serving to about 5 grams to protect your stomach.
4. Buy a third-party tested product. Supplements don’t need FDA approval before they are sold. The NIH points to certification programs such as NSF Certified for Sport, Informed Choice and BSCG, which check that products contain what the label says. Even creatine researchers warn against cheap products of unknown purity. Our guide to the best creatine supplements compares options.
5. Tell your doctor, especially before blood tests, so a higher creatinine isn’t mistaken for kidney trouble.

The bottom line: for healthy adults, creatine’s real side effects are early water weight and stomach upset from big doses, both easy to manage. The kidney, dehydration, cramp and hair-loss fears aren’t supported by controlled studies. If you have kidney disease or bipolar disorder, or are pregnant, get personal advice first. For more free health calculators, browse all our tools.

This article is for general information and is not medical advice. Please read our medical disclaimer.

Most stomach upset comes from large single doses during loading. Our guide to the creatine loading phase explains whether you need to load at all and how long creatine takes to work without it.

Sources

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