Creatine is not "bad for your kidneys." Where do you people get this $hit?[/quote]
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).
To date, no study of creatine use in healthy individuals has provided evidence of harm to these organs (1, 22, 23, 24, 25, 26).
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).
Another popular study often cited in the media reported kidney disease in a male weightlifter who supplemented with creatine (28).
However, this single case study is insufficient evidence. Numerous other factors, including additional supplements, were also involved (26, 28).
That said, creatine supplements should be approached with caution if you have a history of liver or kidney issues.
Current research suggests that creatine does not cause liver or kidney problems.
Does It Cause Digestive 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).
For this reason, the recommended serving is set at 3–5 grams. The 20-gram loading protocol is also split into four servings of 5 grams each over the course of a day (1).
One leading researcher reviewed several studies and concluded that creatine does not increase digestive problems when taken at recommended doses (30).
However, it is possible that additives, ingredients, or contaminants generated during the industrial production of creatine can lead to issues (21, 31).
It is therefore recommended that you purchase a trusted, high-quality product.
Creatine does not increase digestive issues when the recommended dosages and loading guidelines are followed.
How Does It Interact With Other Drugs?
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).
Creatine can help improve blood sugar management, so if you are using medication known to affect blood sugar, you should discuss creatine use with a doctor (5).
You should also consult a medical professional if you are pregnant, breastfeeding, or have a serious condition, such as heart disease or cancer.
Creatine may cause problems if you take certain types of medications, including medications that affect blood sugar.
Other Potential Side Effects
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.
Studies lasting as long as three years have uncovered no negative effects of creatine in children (1, 4, 34).
Research has consistently confirmed creatine’s excellent safety profile. There is no evidence that it causes adverse conditions like rhabdomyolysis or compartment syndrome.
The Bottom Line
Creatine has been used for more than a century, and over 500 studies support its safety and effectiveness.
It also provides many benefits for muscle and performance, may improve markers of health, and is being used in medical settings to help treat a variety of diseases (1, 4, 5).
At the end of the day, creatine is one of the cheapest, most effective, and safest supplements available.