Is Creatine Safe? What Long-Term Studies Show

For healthy adults taking 3 to 5 g a day, creatine is one of the safest supplements studied. Trials have run for up to five years, and the International Society of Sports Nutrition concluded that there's no compelling evidence it harms the kidneys in healthy or clinical populations. The only side effect that turns up consistently is a small gain in weight from water held inside muscle.

That doesn't mean it's right for everyone. Below is what the research shows for each common worry, and the groups who should talk to a doctor before starting.

A note from me, Tom: I've taken creatine daily for about ten years. That's one person's experience and proves nothing on its own, which is why everything below links to the studies instead.

The short answer, by concern

Concern	What the evidence shows	Grade
Kidney damage	No harm in healthy people at normal doses	Good
Liver damage	No harm found in controlled trials	Good
Dehydration and cramps	Not supported; some studies found fewer cramps	Good
Hair loss	No effect when hair was measured directly	Early
Weight gain	Yes, usually 0.5–2 kg of water in the first weeks	Good
Stomach upset	Mainly with large single doses	Good
Long-term use	Studied for up to 5 years without safety problems	Good

Kidneys

This is the most common worry, and it mostly comes from a misunderstanding about a blood test.

When creatine is used by your muscles, it breaks down into creatinine. Doctors measure creatinine in your blood to estimate how well your kidneys are filtering. Taking creatine raises your creatinine a little, simply because there's more creatine to break down. That can make a routine blood test look like your kidneys are struggling when they're working normally.

Studies that measured kidney function more directly have found no harm in healthy people. The ISSN's review covered trials lasting up to five years, including doses far higher than 5 g a day (Kreider et al., 2017).

What to do: - Tell your doctor you take creatine before any blood test. They may want to use a different kidney marker, such as cystatin C. - If you already have kidney disease, don't start creatine without your doctor's approval. The research on healthy kidneys doesn't automatically apply to damaged ones.

Liver

Controlled trials haven't found creatine damages the liver. A review of creatine studies in women found no adverse effects on the liver, kidneys, heart or gut. The liver concern tends to come from cases involving multi-ingredient products or anabolic steroids, where creatine was one of many things being taken.

Dehydration and cramps

The old advice was that creatine pulls water into muscles and leaves the rest of your body dry, causing cramps and heat illness. Researchers who reviewed the studies found no evidence for this. Several studies in athletes training in the heat found creatine users had the same or fewer cramps and injuries than those who didn't take it.

Drink normally. There's no need to force extra water because you take creatine.

Hair loss

The worry comes from a single 2009 study of 20 rugby players that found a rise in a hormone called DHT. It never measured hair. In 2025, a 12-week randomized trial gave 45 men 5 g a day and examined their hair directly: no difference from placebo in DHT or hair density. One trial in men only isn't the final word, but nothing in the research suggests creatine causes hair loss.

Weight gain and water

This one is real, and it's harmless. Creatine draws water into your muscle cells, so many people gain about 0.5 to 2 kg (1 to 4 lb) on the scale in the first weeks, mostly during a loading phase. It's water inside muscle, not fat, and not the puffy fluid under the skin. Our page on creatine bloating and water weight explains how to minimize it.

Stomach upset

Large single doses are the usual cause. In a study of soccer players, a single 10 g dose caused diarrhea in 56%, while the same amount split into two 5 g doses was no worse than placebo. Stick to 3 to 5 g at a time and the problem usually disappears.

Long-term use

The longest studies have followed people for up to five years at doses well above 5 g a day, without safety problems emerging (Kreider et al., 2017). Shorter studies have tracked athletes through whole competitive seasons. There's no evidence you need to cycle off.

Who should talk to a doctor first

Anyone with kidney or liver disease, including people with diabetes or high blood pressure who have been told their kidney function is reduced.
People who are pregnant or breastfeeding. Researchers are interested in creatine during pregnancy, but the evidence isn't there yet.
Under-18s. Studies in teenagers are limited, so this is a decision for a parent and doctor together.
Anyone with bipolar disorder, or taking medication for depression. There are case reports of creatine triggering mania in people with bipolar disorder.
Anyone taking medications that affect the kidneys, such as some anti-inflammatory painkillers (NSAIDs) taken regularly, lithium or certain diuretics.

How to take it as safely as possible

Buy plain creatine monohydrate from a brand with independent testing, such as NSF Certified for Sport or Informed Sport. Supplements aren't checked by regulators before sale. See the best form of creatine.
Take 3 to 5 g a day, split if your stomach is sensitive. Our creatine dosage guide has the details.
Tell your doctor you take it, especially before blood tests.
Stop and see a doctor if you notice anything unusual, such as swelling, a big change in how often you urinate, or persistent stomach problems.

Questions people ask

Can creatine damage your kidneys?

Not in healthy people at normal doses, according to studies lasting up to five years. It does raise creatinine on blood tests, which can look like a kidney problem when there isn't one. If you already have kidney disease, check with your doctor first.

Is creatine safe for teenagers?

Studies in under-18s are limited and haven't shown harm, but this is a decision for a parent and doctor together. Training and eating enough protein matter far more at that age.

Can you take creatine with caffeine?

Yes. Early research suggested caffeine might reduce creatine's effect, but later studies haven't found a meaningful problem. Very high caffeine intake may make stomach upset more likely.

Does creatine raise blood pressure?

Controlled studies haven't found that it does. If you have high blood pressure, especially with reduced kidney function, check with your doctor before starting.

Written by Tom D

Tom has trained in the gym for years and has taken 5 g of creatine every day for about a decade, with magnesium on and off for most of the year. Reading the research behind supplements started as a hobby; this site is where he writes it up. He isn't a doctor or dietitian, so every claim links to the study behind it.

Sources

We link to the original study wherever we can. Read how we grade evidence and choose products.