Diarrhea and Heartburn on Zepbound or Ozempic: What the Dose Tables Show

The short answer

Diarrhea on Zepbound rises with dose: 19% at 5 mg, 21% at 10 mg and 23% at 15 mg, against 8% on placebo, and most of it happens in the weeks after a dose increase¹. Heartburn-type symptoms are less common, with reflux at 4% to 5% and indigestion at 9% to 10%. Ozempic, studied at diabetes doses, sits lower for both.

Elena Voss is a mother writing for mothers, not a treating clinician, and holds no medical license. Every clinical figure here is cited inline to its primary source, the trial or the FDA label, so you can check it. This is background reading, not medical advice.

The rates, side by side

These are the adverse-reaction tables from four current labels. Zepbound and Wegovy come from weight-loss trials; Ozempic and Mounjaro from type 2 diabetes trials at lower exposures, which is part of why their numbers are smaller.

Sources: Zepbound Table 1¹; Wegovy Table 3²; Ozempic section 6.1³; Mounjaro Table 1 and section 6.1⁴.

Two cautions before you use it. The placebo rows matter: Wegovy's 30% diarrhea looks alarming until you see 16% on placebo in the same trials. And the labels themselves warn that rates from one drug's trials cannot be directly compared with another's². Read down each drug, not across them.

Why diarrhea climbs while constipation falls

Zepbound's own table holds a surprise. Diarrhea, nausea and vomiting all rise from 5 mg to 15 mg, but constipation goes the other way, from 17% at 5 mg to 11% at 15 mg¹. We covered that pattern in constipation on a GLP-1. These are different groups of people randomized to different doses, so the table cannot promise that your own diarrhea will worsen at each step. It does say that across thousands of people, diarrhea tracked dose.

The timing is the more useful finding. Zepbound's label says most nausea, vomiting and diarrhea happened during dose escalation and decreased over time; Wegovy's says its stomach side effects were reported most often during escalation as well^1,2. Severe stomach side effects also rose with Zepbound dose, from 1.7% at 5 mg to 3.1% at 15 mg, against 1% on placebo¹. On Wegovy, 0.7% stopped the drug because of diarrhea, against 0.1% on placebo².

For a mother, that means planning around the step-up weeks. A dose increase the week of a road trip, a school event or a stomach bug in the house is worth moving if your prescriber agrees. Zepbound's label also allows a lower maintenance dose when a higher one is not tolerated¹.

Heartburn and the slowed stomach

Zepbound delays stomach emptying, which the label names as the reason it can interfere with oral contraceptives and why it flags aspiration risk under anesthesia¹. Food sitting longer in the stomach is also a plausible route to reflux, and the research has started to measure it.

A 2025 meta-analysis in Gastroenterology pooled 55 placebo-controlled trials with 106,395 participants. Drugs in this class roughly doubled the risk of a GERD diagnosis (risk ratio 2.19), which works out to about 4 extra cases per 1,000 people. The excess looked larger in obesity trials, with weight-loss doses and with higher doses, though those subgroup differences were not statistically significant⁵.

A large population study the same year followed 24,708 people with type 2 diabetes starting a GLP-1 drug and 89,096 starting an SGLT-2 inhibitor in the UK. Over about three years, the GLP-1 group had a 27% higher risk of a new GERD diagnosis, an absolute difference of 0.7 per 100 people, and more GERD complications, about 0.8 extra per 1,000⁶. The authors flag that they could not account for diet and lifestyle⁶.

Put plainly: reflux on these drugs is real, it is usually mild, and the absolute numbers are small. If you had heartburn in pregnancy, the burning may feel familiar. The usual advice of smaller meals and not lying down soon after eating comes from reflux care in general, not from trials of these drugs, so treat it as reasonable rather than proven. Reflux that wakes you at night or does not settle is worth raising, because it can be treated.

Diarrhea and the pill

This is the section most diarrhea pages skip. Zepbound's label already tells women on oral contraceptives to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and 4 weeks after each dose increase, because the delayed stomach emptying can reduce how well the pill works¹. The Wegovy label carries no such instruction².

Diarrhea is a separate problem on top of that. The CDC's contraception guidance says vomiting or severe diarrhea could, in theory, reduce the effectiveness of combined pills, and it handles those episodes using the missed-pill rules, while noting that no direct evidence on the question exists⁷. The weeks after a Zepbound dose increase are the weeks both risks stack up. If you rely on the pill, ask your prescriber which method fits, and see GLP-1s and birth control.

When to call

The medication guides are specific. Diarrhea, nausea and vomiting can dehydrate you enough to harm the kidneys, so drink fluids and call your prescriber right away if they do not stop^1,2. Stop the drug and call right away for severe stomach pain that will not go away, sometimes felt through to the back, which can signal pancreatitis. Call right away for upper stomach pain with fever, yellowing skin or eyes, or clay-colored stools, which can signal gallbladder trouble¹. Our page on gallbladder risk in women covers the last of these. For gas and swelling rather than loose stools, see bloating and gas, and for the wider picture, the GLP-1 providers for women board.

Where this sits on the evidence scale

The diarrhea figures are strong: placebo-controlled trial data printed in four FDA labels, consistent in showing the rise with dose and the clustering around dose increases. The reflux evidence is moderate: a meta-analysis of randomized trials and a large cohort agree there is a small real increase, though the cohort cannot rule out lifestyle confounding. Advice on managing either symptom on these specific drugs has not been tested in trials, and the contraception guidance for diarrhea rests on reasoning rather than data.