Creatine: What It Is, Evidence, Tolerability and Safety

Overview

Creatine is a natural compound the body makes and also takes in from food, mainly red meat and seafood. [1] The body forms it from the amino acids arginine, glycine and methionine in the kidneys and liver. [2] As a supplement it is sold mostly as creatine monohydrate powder. It is a separate topic from collagen: they are different substances with different evidence (see Collagen supplements).

Creatine is not an anabolic steroid: it has a different chemical structure and is regulated as a dietary supplement. [2] In the United States, a position paper reports the FDA classified creatine as "generally recognized as safe" (GRAS) in late 2020. [2] That is a regulatory status, not a promise it suits everyone.

How the evidence is labeled

Established role means a proven job in the body; evidence in adequately nourished people means trials in people with no deficiency; promising but limited, mixed, insufficient evidence and Proper evidence not found mean what they say.

What the research shows

Details for older adults, women, vegetarians and memory are on Creatine for older adults, women and cognition.

Amounts used in research

These describe studies. They are not personal advice, and a US or UK label may differ.

• Maintenance-style: about 3 to 5 g a day, or 0.1 g per kg of body mass a day, is described as effective for raising muscle creatine over time. [2]
• Loading: 5 to 7 days at 20 to 25 g a day, often split into smaller servings, then a lower daily amount. [2]
• Is loading required? A review concludes it is not: in one comparison, muscle creatine rose by a similar amount (about 20%) after 3 g a day for 28 days or 20 g a day for 6 days. [2] Loading just gets there faster.
• Food comparison: meat has about 0.7 g of creatine per 6 oz serving, a point used to put supplement amounts in context. [2]

Water weight, stomach and other common worries

• Water-related weight change: the most common effect reported early on is water retention in the first several days. [2] Longer training studies of 5 to 10 weeks often found no increase in total body water. [2] A small trial in vegan adults did measure about 1.4 kg more total body water after 4 weeks. [8]
• Stomach upset: single servings above about 10 g may cause diarrhea, which is why loading is split into smaller doses. [2]
• Hair loss: the available evidence does not show creatine raises testosterone or DHT or causes hair loss. [2]
• Cramps and dehydration: a position paper found no evidence that creatine increases injuries, dehydration, cramping, stomach upset or kidney problems in athletes followed up to 3 years. [1]

Kidneys and lab tests

Creatine supplements raise blood creatinine, a number doctors use to estimate kidney function, and a meta-analysis concluded this likely reflects altered creatinine handling rather than kidney injury. [9] See Creatine, kidney questions and creatinine testing. If you have kidney disease or take medicines that affect the kidneys, speak to your clinician first; concerns persist for people with impaired kidney function. [10]

Who should be cautious

• Children and teens: whether the adult safety findings apply is described as relatively unclear. [2]
• Pregnancy: the review found no human studies of creatine supplementation during pregnancy. [2] See Pregnancy and breastfeeding.
• Medicines and conditions: the sources I read did not give a drug-interaction list for creatine. Proper evidence not found. See How interactions work.

Forms, purity and labels

Monohydrate is the form with the most research. [11] Other forms are covered in Creatine forms and products. Quality problems have been reported: in one study of 149 creatine products, 32 were classed as adulterated. [12] See Quality testing and certifications.