Creatine, questioned.

Creatine monohydrate has an unusually large research record for a sports supplement. That does not make it appropriate for every person, but it does let us separate common side effects from common myths.

A 2025 analysis reviewed 685 human creatine trials, covering 12,839 participants receiving creatine and 13,452 receiving placebo, with study durations extending as long as 14 years. It found no overall difference in the prevalence of the 35 evaluated side effects or health markers.^[1] Because reporting quality varied and rare harms can evade even large datasets, this supports reassurance, not a claim of zero risk.

Does creatine harm the kidneys?

In healthy people using recommended amounts, controlled studies have not shown impaired kidney filtration. A 2025 systematic review and meta-analysis found a small rise in serum creatinine but no significant change in glomerular filtration rate.^[2]

Why a blood test can look different

Creatine naturally breaks down into creatinine. Because serum creatinine is commonly used to estimate kidney function, supplementation can change that marker without changing actual filtration.^[3] Tell the clinician ordering or interpreting your laboratory work that you take creatine rather than trying to interpret an isolated result yourself.

Does creatine cause dehydration or cramping?

The controlled literature does not support the claim that creatine causes dehydration or muscle cramps. Reviews include studies of exercise, heat, and athletes in which cramping and injury were not increased.^[4]

The 2025 safety analysis did find that more creatine studies mentioned cramping or pain, but at the participant level the difference from placebo was not statistically significant.^[1] Normal hydration matched to activity, climate, and individual needs is sensible; creatine does not create a special requirement to force excessive water intake.

Does creatine cause hair loss?

The concern grew largely from a small 2009 study that reported a change in dihydrotestosterone after loading, but it did not measure hair loss. A direct 2025 randomized trial gave 5 grams daily to resistance-trained men for 12 weeks and found no difference from placebo in DHT, the DHT-to-testosterone ratio, hair density, follicular units, or cumulative hair thickness.^[5]

That is reassuring direct evidence, but the study was small, short, and limited to men aged 18–40. It cannot establish lifetime risk in every population. The accurate conclusion is that current direct evidence does not show that 5 grams of creatine daily causes hair loss, while longer and broader studies would improve certainty.

What side effects are plausible?

Early water weight

Loading can add roughly 1–3 kilograms in the short term, primarily through water associated with muscle creatine storage, not body fat.^[3] A no-load protocol of 3–5 grams daily tends to make that transition more gradual.

Gastrointestinal discomfort

Large single servings can cause loose stool or stomach discomfort. In a randomized trial, taking 10 grams at once caused more diarrhea than splitting the same daily amount into two 5-gram servings.^[6]

When to pause and ask first

• Known kidney disease or abnormal kidney tests: discuss the decision and monitoring with your clinician.
• Pregnancy or breastfeeding: human safety and dosing data remain inadequate; do not self-start based on animal or theoretical research.^[7]
• Under age 18: involve a pediatric clinician and qualified sports professional.
• Complex conditions or medications: ask the professional who understands the full picture, especially when kidney function or fluid balance is relevant.
• Unexplained symptoms: stop and seek appropriate medical evaluation rather than assuming a supplement is or is not responsible.

For a healthy adult who has cleared those questions, the evidence-based routine remains simple: 3–5 grams of creatine monohydrate daily, with no required loading phase and no need to cycle.^[3]