Should you worry about the side effects of creatine? • Stronger by Science

Creatine is one of the most studied supplements in sports nutrition. It’s also one of the most misunderstood in terms of side effects. Despite decades of evidence suggesting it’s safe and effective, concerns about side effects – especially kidney and liver damage and hair loss – continue to be commonplace. In this newsletter, we’ll cover the research on potential side effects of creatine.

A new paper by Kreider et al sought to summarize the available research on creatine side effects and public sentiment towards creatine. The authors pulled together 104 studies reporting side effect data from a pool of more than 26,000 participants across 652 clinical trials on creatine supplementation. The result is probably the most comprehensive look to date at whether creatine supplementation actually has any notable side effects – and if so, which ones.

Statistically, the difference in overall side effect frequency wasn’t significant. 4.60% of creatine users reported a side effect versus 4.21% of placebo users (p = 0.828). So already, we’re talking about a 0.39% difference that wasn’t statistically significant by a long shot.

Looking specifically at the most commonly cited issues – gastrointestinal symptoms and cramping – there still was no cause for concern. GI side effects were reported by 5.51% of creatine users and 4.05% of placebo users (p = 0.820), and cramping/pain was reported by 0.52% of creatine users versus 0.07% of placebo users (p = 0.085). The latter might seem like a big difference, but in absolute terms, that’s less than half a percentage point difference in both cases.

In fact, across the 35 different side effects evaluated – everything from dizziness and diarrhea to skin complications and cardiac conditions – none showed a consistent difference between creatine and placebo. Even in studies where creatine was taken for years at a time or in clinical populations like participants with Parkinson’s disease, side effect rates didn’t appear higher.

The authors also reviewed 50 years of adverse event reports submitted to regulatory agencies like the FDA. Of 28.4 million reports in total, just 345 mentioned creatine at all – about 0.0072%. Of those, only 203 confirmed creatine was in the product used. In 46.3% of the reports, creatine was listed even though it wasn’t an ingredient. Just 15.8% involved actual creatine-only products, and 63% involved other substances, including energy drinks, herbs, and stimulants. In short: even in the event that someone bothered to submit a formal adverse report, creatine was rarely the only ingredient in the products reported, and when creatine was present, it was usually part of a pretty complex multi-ingredient supplement (i.e. with multiple confounders).

Though this wasn’t the focus of this review, another common concern with creatine’s side effects is around creatine causing hair loss. This claim stems almost entirely from a single study published in 2009, which found that a group of male rugby players taking creatine experienced an increase in dihydrotestosterone (DHT), a hormone associated with hair loss in individuals predisposed to male pattern baldness. However, this increase in DHT was modest, within normal physiological ranges, and has never been directly linked to actual hair loss. More importantly, no study to date has demonstrated that creatine supplementation causes or accelerates hair loss in humans. In fact, the 2009 study didn’t measure hair loss at all – only hormone levels. Fortunately, since then, a study has been published measuring actual hair loss from creatine supplementation; as expected, creatine didn’t result in any hair loss. To summarize, hair loss probably isn’t something to worry about with creatine supplementation.

So if clinical trials don’t show much, and adverse event databases don’t show much, why do people still believe creatine has side effects?

To answer that, the authors analyzed over 129,000 YouTube comments and 657,000 tweets mentioning creatine. The average sentiment was slightly positive, but when the tone of the comment was stronger – either strongly positive or strongly negative – negativity tended to dominate. In other words, most people didn’t seem to have strong opinions either way, but the ones who felt the most strongly about creatine were more likely to be anti-creatine.

The overall takeaway is pretty simple: creatine has very few, if any, side effects. Whether we’re looking at short-term trials, long-term trials, high doses, clinical populations, adverse event reporting, or public health surveillance, there’s no consistent evidence that creatine supplementation increases the risk of side effects beyond placebo.