Creatine is the number-one sports performance supplement available.
Yet despite its research-backed benefits, some people avoid creatine because they're afraid it’s bad for health.
Some claim it causes weight gain, cramping, and digestive, liver, or kidney problems.
This article provides an evidence-based review of creatine's safety and side effects.
Depending on who you ask, the suggested side effects of creatine may include:
- Kidney damage
- Liver damage
- Kidney stones
- Weight gain
- Muscle cramps
- Digestive problems
- Compartment syndrome
Additionally, some people wrongly claim that creatine is an anabolic steroid, that it's unsuitable for women or teenagers, or that it should only be used by professional athletes or bodybuilders.
Leading researchers who have studied creatine for several decades also conclude that it is one of the safest supplements on the market (2).
One study examined 52 health markers after participants took creatine supplements for 21 months. It found no adverse effects (2).
SUMMARY Although claims abound about creatine’s side effects and safety issues, none of them are supported by research.
Creatine is found throughout your body, with 95% stored in your muscles (6).
However, your diet and natural creatine levels do not normally maximize muscle stores of this compound.
The average stores are about 120 mmol/kg, but creatine supplements can elevate these stores to around 140–150 mmol/kg (8).
Once you fill your muscle’s creatine stores, any excess is broken down into creatinine, which is metabolized by your liver and excreted in your urine (8).
SUMMARY Around 95% of the creatine in your body is stored in your muscles. There, it provides increased energy for high-intensity exercise.
This fact may be behind the theory that creatine causes dehydration. However, this shift in cellular water content is minor, and no research supports the claims about dehydration.
A three-year study of college athletes found that those taking creatine had fewer cases of dehydration, muscle cramps, or muscle injuries than those not taking it. They also missed fewer sessions due to illness or injury (11).
One study examined creatine use during exercise in hot weather, which can accelerate cramping and dehydration. During a 35-minute cycling session in 99°F (37°C) heat, creatine had no adverse effects compared to a placebo (12).
Further examination via blood tests also confirmed no difference in hydration or electrolyte levels, which play a key role in muscle cramps (12).
The most conclusive research has been conducted in individuals undergoing hemodialysis, a medical treatment that may cause muscle cramps. Researchers noted that creatine reduced cramping incidents by 60% (13).
Based on the current evidence, creatine does not cause dehydration or cramping. If anything, it may protect against these conditions.
SUMMARY Contrary to popular belief, creatine does not increase your risk of cramps and dehydration — and, in fact, may reduce your risk of these conditions.
Research has thoroughly documented that creatine supplements cause a quick increase in body weight.
Over the long term, studies show that body weight may continue to increase to a greater extent in creatine users than in non-creatine users. However, weight gain is due to increased muscle growth — not increased body fat (15).
For most athletes, the additional muscle is a positive adaptation that may improve sports performance. As it is also one of the main reasons people take creatine, it should not be considered a side effect (1, 14).
SUMMARY Weight gain from creatine is due not to gaining fat but to increased water content within your muscles.
Creatine can slightly raise levels of creatinine in your blood. Creatinine is commonly measured to diagnose kidney or liver problems.
However, the fact that creatine raises creatinine levels does not mean that it is harming your liver or kidneys (21).
A long-term study of college athletes found no side effects related to liver or kidney function. Other studies measuring biological markers in the urine also found no difference after creatine ingestion (27).
One of the longest studies to date — lasting for four years — similarly concluded that creatine has no negative side effects (24).
That said, creatine supplements should be approached with caution if you have a history of liver or kidney issues.
SUMMARY Current research suggests that creatine does not cause liver or kidney problems.
As with many supplements or medications, excessive doses may cause digestive issues.
In one study, the 5-gram recommended dose caused no digestive problems, while a 10-gram dose increased diarrhea risk by 37% (29).
One leading researcher reviewed several studies and concluded that creatine does not increase digestive problems when taken at recommended doses (30).
It is therefore recommended that you purchase a trusted, high-quality product.
SUMMARY Creatine does not increase digestive issues when the recommended dosages and loading guidelines are followed.
As with any diet or supplement regimen, it is best to discuss your creatine plans with a doctor or other medical professional before you start.
You may also wish to avoid creatine supplements if you are taking any medications that affect liver or kidney function.
Medications that may interact with creatine include cyclosporine, aminoglycosides, gentamicin, tobramycin, anti-inflammatory drugs like ibuprofen, and numerous others (7).
You should also consult a medical professional if you are pregnant, breastfeeding, or have a serious condition, such as heart disease or cancer.
SUMMARY Creatine may cause problems if you take certain types of medications, including medications that affect blood sugar.
Some people suggest that creatine can lead to compartment syndrome, a condition that occurs when excessive pressure builds inside an enclosed space — usually within arm or leg muscles.
Although one study found an increase in muscle pressure during two hours of heat training, it resulted mainly from heat and exercise-induced dehydration — not from creatine (32).
Researchers also concluded the pressure was short-lived and insignificant.
Some claim that creatine supplements increase your risk of rhabdomyolysis, a condition in which muscle breaks down and leaks proteins into your bloodstream. However, this idea is not supported by any evidence.
The myth originated because a marker in your blood called creatine kinase increases with creatine supplements (32).
However, this slight increase is quite different from the large amounts of creatine kinase associated with rhabdomyolysis. Interestingly, some experts even suggest creatine may protect against this condition (32, 33).
Some people also confuse creatine with anabolic steroids, but this is yet another myth. Creatine is a completely natural and legal substance found in your body and in foods — such as meat — with no link to steroids (7).
Finally, there is a misconception that creatine is suitable only for male athletes, not for older adults, women, or children. However, no research suggests that it is unsuitable in recommended doses for women or older adults (1).
Unlike most supplements, creatine has been given to children as a medical intervention for certain conditions, such as neuromuscular disorders or muscle loss.
SUMMARY Research has consistently confirmed creatine’s excellent safety profile. There is no evidence that it causes adverse conditions like rhabdomyolysis or compartment syndrome.
Creatine has been used for more than a century, and over 500 studies support its safety and effectiveness.
At the end of the day, creatine is one of the cheapest, most effective, and safest supplements available.