About 12,000 searches a month ask whether creatine causes constipation, or the reverse, whether it makes you poop. The second question has a trial behind it. The first has almost nothing, and the reason is worth stating: the studies that recorded creatine's gut effects were looking for loose stools and stomach upset, and constipation was rarely counted at all.
This page sets out what each record shows and where it stops. It is not medical advice.
What 685 trials counted
The largest analysis of creatine's side effects (Kreider et al., J Int Soc Sports Nutr 2025) pooled 685 creatine study groups and 652 placebo groups. Its list of 49 side effects has rows for diarrhoea, nausea and "gastrointestinal/abdominal" complaints. Constipation has no row of its own. Whatever constipation was reported sits, unseparated, inside the gut category:
| Gastrointestinal/abdominal complaints | Placebo | Creatine | p |
|---|---|---|---|
| Study groups reporting any | 28 of 652 (4.3%) | 63 of 685 (9.2%) | < 0.001 |
| Share of participants | 4.05% | 5.51% | 0.820 |
Counted by study, gut complaints were reported about twice as often in creatine groups. Counted by person, the difference was small and not significant. That gap is the usual sign that a few studies reported many complaints, and the single-serving trial below is one of them. Neither count can say how many complaints were constipation.
Two limits apply. The trials averaged far more than the 3–5 g on most labels, and side-effect reporting in supplement trials is uneven. The first author chairs a scientific advisory board supported by a creatine manufacturer, as the paper states.
The direction the trial data point
The one trial that tested serving size found the opposite problem. Among 59 footballers, a single 10 g serving produced diarrhoea in 55.6%, against 28.6% when the same 10 g was split into two 5 g servings and 35.0% on placebo (Ostojic 2008). That trial, and why the placebo rate was so high, is the subject of the creatine and diarrhoea page. Every gut finding in that trial points towards looser stools, not harder ones.
What the FDA's report database holds
The FDA's database of adverse-event reports for foods and supplements (CAERS, read through openFDA on 6 October 2026, data updated 7 July 2026) holds 210 reports naming a product with "creatine" in its brand name.
| Reaction listed | Reports |
|---|---|
| Diarrhoea | 9 |
| Abdominal pain (any wording) | 26 |
| Constipation | 3 |
The three constipation reports were filed in 2014, 2019 and 2026. Each lists other problems too: one with rectal prolapse and hypersensitivity, one with diarrhoea, nausea and dehydration in the same report, one with a hardened stool mass (faecaloma) and abdominal pain. Reports like these are unverified, have no denominator and cannot show that creatine caused anything; one listing diarrhoea and constipation together shows how little a single report can settle. Why the whole creatine report set cannot be read as a safety signal is on creatine side effects.
The only study that looked at constipation and creatine together
It is not a supplement study. A 2025 analysis of the US National Health and Nutrition Examination Survey (2005–2010) estimated each person's creatine intake from food over two days, mostly from meat and fish, and compared it with self-reported bowel habits (Zheng et al., Front Nutr 2025):
- Each tenfold higher dietary creatine intake was associated with 19% lower odds of chronic constipation (adjusted odds ratio 0.81, 95% CI 0.65–0.96).
- There was no association with chronic diarrhoea (adjusted OR 1.04).
This is an observational study of diet. People who eat more meat differ from those who eat less in many ways the adjustment cannot fully remove, and a tenfold range of food creatine is not the same thing as a 5 g scoop. It is the only published data set that measured both creatine and constipation, and it points away from constipation, not towards it. How much creatine food supplies is on foods high in creatine.
A 2011 trial in children with Angelman syndrome gave a combination of betaine, folate, creatine and vitamin B12 for a year; constipation was among the adverse events that led some of the 7 withdrawals (Bird et al. 2011). With four supplements given together, none can be singled out.
The census
| Where we looked (6 Oct 2026) | Query | Result |
|---|---|---|
| PubMed | creatine with constipation, bowel movement or stool frequency, excluding "creatine kinase" |
41 records; 2 concern creatine taken by mouth (the two studies above) |
| ClinicalTrials.gov | intervention creatine, condition constipation | 0 creatine studies |
Most of the 41 PubMed records are case reports of thyroid disease or drug trials that mention creatine kinase or creatinine alongside constipation.
Things that change at the same time, untested
Nothing in the record separates creatine from what usually starts with it: more protein and less fibre on a bulking diet, other powders and pre-workouts, and shifts in how much someone drinks. Creatine draws water into muscle, and a common claim is that this leaves less for the gut; no study has tested that chain. This page lists these as unmeasured, not as explanations.
What is not established
- Whether creatine causes constipation. No trial has counted it separately.
- Whether forms differ. No constipation data exist for creatine hydrochloride, gummies or capsules.
- Whether the dietary association reflects creatine or meat. The survey study cannot say.
Constipation lasting more than a few weeks, or with pain, blood or weight loss, is a reason to see a clinician, whatever supplement is involved.
Sources and dates
- Kreider RB et al. Safety of creatine supplementation: analysis of the prevalence of reported side effects in clinical trials and adverse event reports. J Int Soc Sports Nutr 2025, PMID 40198156; Tables 2 and 3 read in PMC11983583.
- Ostojic SM, Ahmetovic Z. Gastrointestinal distress after creatine supplementation in athletes: are side effects dose dependent? Res Sports Med 2008;16:15–22, PMID 18373286.
- Zheng B et al. Association of dietary creatine intake from meat protein sources with different types of intestinal problems: insights from NHANES 2005–2010. Front Nutr 2025;12:1586569, PMID 40786687.
- Bird LM et al. A therapeutic trial of pro-methylation dietary supplements in Angelman syndrome. Am J Med Genet A 2011;155A:2956–63, PMID 22002941.
- US FDA CAERS via openFDA food/event,
products.name_brand:creatine(210 reports), reactions counted case-insensitively; data updated 2026-07-07, read 2026-10-06. - PubMed and ClinicalTrials.gov API v2 searches as tabled above, run 2026-10-06.