Creatine Side Effects: What Is Real, What Is a Myth, and Who Should Avoid It

At 3–5 g a day, creatine monohydrate has few side effects in healthy adults. The ones that are real are mild: 1–2 kg of water weight in the first weeks, stomach upset if you take large single doses, and a higher creatinine number on blood tests that can be mistaken for a kidney problem. The famous ones — kidney damage, dehydration, cramps and hair loss — are not supported by controlled trials in healthy people. People with kidney disease are the clear exception.

Creatine is one of the most studied supplements there is, with hundreds of trials and studies lasting up to five years. Here is each reported side effect, what the evidence actually says, and who should be careful.

How this article was put together

I read the position stands and reviews of the International Society of Sports Nutrition, recent meta-analyses on kidney function, and the individual trials behind the most common worries, all listed under Sources. I have not run any trial myself. Dose figures refer to creatine monohydrate. This is general information, not medical advice.

Side effects that are real

1. Water weight gain

The most consistent effect. Creatine pulls water into muscle cells, so body weight usually rises by about 1–2 kg in the first weeks, more with a 20 g loading phase (1–3 kg). This is water inside the muscle, not fat, and it is not “bloat” under the skin. Taking 3–5 g a day without loading makes the change smaller and slower. The full detail is in does creatine make you gain weight?

2. Stomach upset and diarrhoea

Mostly a dose problem. In a study of athletes by Ostojic and Ahmetovic (2008), a single 10 g dose caused diarrhoea more often than two 5 g doses or placebo. The fix: keep each dose at 5 g or less, take it with food and enough water, and skip loading if your stomach is sensitive. Poorly dissolved powder can also irritate; micronized powders mix better.

3. Higher creatinine on blood tests

This one matters because it can lead to a wrong diagnosis. Creatine breaks down into creatinine, the marker doctors use to estimate kidney function. Taking creatine raises blood creatinine, so the calculated kidney score (eGFR) can look worse even when the kidneys are fine. A 2025 meta-analysis in BMC Nephrology found exactly that: creatinine rose modestly, but glomerular filtration rate did not fall. If you take creatine, tell your doctor before a blood test; a cystatin C test or a measured GFR gives a clearer picture.

Side effects the evidence does not support

Kidney damage

In healthy people, controlled trials have not found kidney harm at normal doses, including a randomized trial by Gualano and colleagues in 2008 and one in people with type 2 diabetes in 2011. Meta-analyses in 2019 and 2025 reached the same conclusion. The worry comes largely from a handful of case reports, often involving high doses, other supplements or existing kidney disease. A 2026 meta-analysis that also included people with chronic kidney disease found higher creatinine and lower creatinine-based kidney scores, which is expected from the creatinine effect above but is a reason for anyone with kidney disease to use creatine only under medical supervision.

Dehydration and muscle cramps

Early surveys of athletes reported cramps, but controlled studies have not confirmed them. In a season-long trial in college football players training in heat and humidity, those taking creatine had less cramping, heat illness and dehydration than those who did not. A 2009 meta-analysis found that creatine did not impair heat tolerance or hydration. Drink normally; you do not need extra water beyond your usual habits.

Hair loss

Based on a single 2009 study of 20 rugby players in which DHT, a hormone linked to male-pattern baldness, rose during creatine loading. Nobody measured hair, and no study since has repeated the DHT finding or shown hair loss. A 2025 trial looking directly at hair found no effect. Full detail in does creatine cause hair loss?

Liver damage, acne, “steroid” effects

Creatine is not a steroid and does not act on hormone receptors. Trials measuring liver enzymes in healthy adults have not found harm at normal doses. Acne is sometimes reported anecdotally, but there is no controlled evidence linking it to creatine.

Who should be careful

• Kidney disease, a single kidney or a kidney transplant: only with your doctor’s agreement, and expect your creatinine to rise.
• Medicines that strain the kidneys (for example regular high-dose NSAIDs or some diuretics): ask your doctor or pharmacist.
• Pregnancy and breastfeeding: creatine is being researched for pregnancy, but there is not enough safety data to recommend it.
• Bipolar disorder: there are case reports of mania in people with bipolar disorder taking creatine; talk to your psychiatrist first.
• Teenagers: studies in adolescents have not shown harm, but most health bodies advise against supplements for under-18s unless supervised.

How to minimise side effects

• Take 3–5 g a day and skip the loading phase. More is not better once your muscles are full.
• Keep single doses at 5 g or less, with food and a full glass of water.
• Use plain creatine monohydrate. Blends add other ingredients and other side effects.
• Choose a certified product. NSF Certified for Sport or Informed Choice reduces the risk of contamination or a wrong dose. Gummies have a poor testing record; see the best creatine gummies.
• Tell your doctor before blood tests.

Timing does not change side effects much; see creatine before or after a workout.

If you want a low-risk product

The simplest way to avoid surprises is a plain monohydrate powder whose testing you can check in a public register. Two from my best creatine comparison:

Optimum Nutrition Micronized Creatine — 5 g per scoop, nothing added, Informed Choice certified, about 23¢ a day.

Check current prices on Amazon

Thorne Creatine — 5 g per scoop, nothing added, NSF Certified for Sport, about 49¢ a day.

Check current prices on Amazon

For women, including over 40, see the best creatine for women.

As an Amazon Associate I earn from qualifying purchases. This never changes a score, a ranking or a verdict — those are decided before any commercial link is considered.

Wondering when you will see results? How long creatine takes to work gives the week-by-week timeline.

Taking creatine inside a pre-workout? Most of those side effects come from the caffeine; see pre-workout side effects.

Common questions

What are the side effects of creatine?

In healthy adults at 3–5 g a day: water weight gain of about 1–2 kg, stomach upset with large single doses, and a higher creatinine reading on blood tests. Kidney damage, dehydration, cramps and hair loss are not supported by controlled trials.

Is creatine bad for your kidneys?

Not in healthy people at normal doses, according to randomized trials and meta-analyses. It raises blood creatinine, which can make a kidney test look worse than it is. People with kidney disease should only take it under medical supervision.

Does creatine cause bloating?

The water it adds is mostly inside muscle. Stomach bloating is usually linked to large single doses or loading; 3–5 g a day with food rarely causes it.

Is it safe to take creatine every day?

Yes for healthy adults. Studies have followed daily use for up to five years without serious side effects, and daily use is how muscle stores stay full.

What happens when you stop taking creatine?

Muscle creatine returns to normal over about four to six weeks, and the extra water weight goes with it. There are no withdrawal effects.

Sources

• Antonio J et al. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show? J Int Soc Sports Nutr. 2021.
• Kreider RB et al. ISSN position stand: safety and efficacy of creatine supplementation. J Int Soc Sports Nutr. 2017.
• Naeini EK et al. Effect of creatine supplementation on kidney function: a systematic review and meta-analysis. BMC Nephrol. 2025.
• Impact of creatine supplementation on kidney health: a systematic review and meta-analysis. Int Urol Nephrol. 2026.
• de Souza e Silva A et al. Effects of creatine supplementation on renal function: a systematic review and meta-analysis. J Ren Nutr. 2019.
• Gualano B et al. Effects of creatine supplementation on renal function: a randomized, double-blind, placebo-controlled clinical trial. Eur J Appl Physiol. 2008.
• Greenwood M et al. Creatine supplementation during college football training does not increase the incidence of cramping or injury. Mol Cell Biochem. 2003.
• Lopez RM et al. Does creatine supplementation hinder exercise heat tolerance or hydration status? A systematic review with meta-analyses. J Athl Train. 2009.
• Ostojic SM, Ahmetovic Z. Gastrointestinal distress after creatine supplementation in athletes: are side effects dose dependent? Res Sports Med. 2008.