Does creatine put a strain on your kidneys?
For healthy people without kidney disease, creatine monohydrate at normal doses is not harmful to the kidneys, although it can raise a blood marker that resembles signs of kidney problems. If you have diabetes, high blood pressure, already reduced kidney function, or are taking medications that are hard on the kidneys, discuss it with your doctor first.
Creatine does not strain your kidneys, but it does raise one blood marker that doctors use to assess kidney function: creatinine. That number rises with creatine use, but the kidneys are doing their job perfectly normally. It is a measurement artefact, not damage. Multiple reviews emphasise this point.
In healthy adults without kidney disease, creatine monohydrate, labelled 'Creatine monohydrate' on the packaging, causes no measurable kidney damage. This holds for a maintenance dose of 3 to 5 grams per day, and also for a loading phase of 20 grams per day over 5 days; safety has been demonstrated in research lasting from 5 days to 5 years. Other kidney function markers, such as protein in the urine and urea, remained normal. The certainty here is reasonable: multiple studies and a meta-analysis point in the same direction. Whether you choose powder or capsules makes no difference; do not choose creatine ethyl ester, because that form causes an additional rise in blood creatinine and may falsely suggest that the kidneys are failing.
One case of acute kidney failure has been reported in a 20-year-old who took 20 grams per day for 4 weeks. That is an isolated case, not evidence in itself. Nevertheless, multiple reviews draw the cautious conclusion from it that creatine may carry risks for people who already have reduced kidney function, diabetes or high blood pressure. In those situations it is wise not to use creatine without consulting your doctor. If you are taking medications that are hard on the kidneys, discuss this with your doctor as well.
In children and adolescents, safety has not been established; there is very little research on the subject. High doses also increase the excretion of certain metabolic waste products, but in healthy people this remains within normal limits and has no demonstrable effect on the kidneys. Creatine is not worth your money if you have kidney disease and have not consulted a doctor, or if you opt for a more expensive creatine variant than monohydrate: those offer no proven advantage.
This answer rests on multiple studies in humans, including several larger review studies and one summary of multiple earlier studies. The evidence for healthy adults is reasonably consistent; for at-risk groups, children, and high doses it is much thinner, based in part on isolated cases or reasoning from mechanism.
Does creatine cause hair loss?
Current research shows that creatine does not raise DHT and has no effect on hair follicle health. There is no need to avoid creatine out of fear of hair loss.
Do you need to do a loading phase with creatine?
A loading phase is not necessary, but it does speed up the build-up of creatine in your muscles. Choose a loading phase if you want fast results, or simply take 3 to 5 grams daily if you have more patience.
Why don't doctors always recommend creatine?
Creatine monohydrate is well supported for strength sports and its safety profile in healthy adults is reassuring, but safety data for children and teenagers are lacking and some proven applications are more limited than the marketing suggests.
What is best not to combine with creatine?
Combining creatine with caffeine powder adds nothing to your performance and increases the risk of gastrointestinal complaints; ready-made pre-workout blends with many ingredients carry additional risks due to possible contamination and unknown long-term effects.
What does creatine do in your body besides building muscle?
Creatine does more in the brain than in the muscles: it buffers energy and protects the brain against stress such as sleep deprivation. For healthy people, however, the effect on cognitive ability is small and most visible under pressure, not at rest.
Does creatine affect your sleep?
Creatine may improve how you experience your sleep, but objective measurements show no effect. The research is based on dozens of participants and the results are contradictory; do not use it as a sleep aid.