Drug facts

Side effects, and how common they are

Reviewed August 2026

Quick answer

The most common are gastrointestinal. In the obesity trials, nausea affected 25–29% of participants against 8% on placebo, and diarrhea 19–23% against 8%. Most other reactions sit in the single digits.

Reactions reported in 5% or more of participants1

Pooled from the two pivotal obesity trials, shown by dose with the placebo rate alongside. The placebo column is the part worth reading: several of these occur without the drug too, and the difference is the signal.

How common each reaction was, by dose

  • Placebo
  • 5 mg
  • 10 mg
  • 15 mg
051015202530NauseaNausea, Placebo: 8%Nausea, 5 mg: 25%29%Nausea, 10 mg: 29%Nausea, 15 mg: 28%DiarrheaDiarrhea, Placebo: 8%Diarrhea, 5 mg: 19%Diarrhea, 10 mg: 21%23%Diarrhea, 15 mg: 23%VomitingVomiting, Placebo: 2%Vomiting, 5 mg: 8%Vomiting, 10 mg: 11%13%Vomiting, 15 mg: 13%ConstipationConstipation, Placebo: 5%17%Constipation, 5 mg: 17%Constipation, 10 mg: 14%Constipation, 15 mg: 11%Abdominal painAbdominal pain, Placebo: 5%Abdominal pain, 5 mg: 9%Abdominal pain, 10 mg: 9%10%Abdominal pain, 15 mg: 10%DyspepsiaDyspepsia, Placebo: 4%Dyspepsia, 5 mg: 9%Dyspepsia, 10 mg: 9%10%Dyspepsia, 15 mg: 10%Injection sitereactionsInjection site reactions, Placebo: 2%Injection site reactions, 5 mg: 6%Injection site reactions, 10 mg: 8%8%Injection site reactions, 15 mg: 8%FatigueFatigue, Placebo: 3%Fatigue, 5 mg: 5%Fatigue, 10 mg: 6%7%Fatigue, 15 mg: 7%Eructation(burping)Eructation (burping), Placebo: 1%Eructation (burping), 5 mg: 4%Eructation (burping), 10 mg: 5%5%Eructation (burping), 15 mg: 5%GastroesophagealrefluxGastroesophageal reflux, Placebo: 2%Gastroesophageal reflux, 5 mg: 4%Gastroesophageal reflux, 10 mg: 4%5%Gastroesophageal reflux, 15 mg: 5%Hair lossHair loss, Placebo: 1%Hair loss, 5 mg: 5%Hair loss, 10 mg: 4%5%Hair loss, 15 mg: 5%HypersensitivityreactionsHypersensitivity reactions, Placebo: 3%Hypersensitivity reactions, 5 mg: 5%Hypersensitivity reactions, 10 mg: 5%5%Hypersensitivity reactions, 15 mg: 5%051015202530% of participants reporting it
Nausea is the most common reaction at every dose — 28% at 15 mg — but 8% of participants on placebo reported it too, and the difference between those two bars, not the height of the first, is the signal. The rates also do not simply climb with the dose: Nausea and Constipation each peak below the highest dose, so a higher dose is not uniformly a worse experience.

Source: FDA prescribing information for ZEPBOUND (tirzepatide), section 6.1, revision 4/2026. Percentages are of participants reporting the reaction at least once, not of doses. They are not a prediction about any individual.

Adverse reactions reported by 5% or more of participants, by dose, with the placebo rate.
ReactionPlacebo5 mg10 mg15 mg
Nausea8%25%29%28%
Diarrhea8%19%21%23%
Vomiting2%8%11%13%
Constipation5%17%14%11%
Abdominal pain5%9%9%10%
Dyspepsia4%9%9%10%
Injection site reactions2%6%8%8%
Fatigue3%5%6%7%
Eructation (burping)1%4%5%5%
Gastroesophageal reflux2%4%4%5%
Hair loss1%5%4%5%
Hypersensitivity reactions3%5%5%5%
ReactionPlacebo5 mg10 mg15 mg
Nausea8%25%29%28%
Diarrhea8%19%21%23%
Constipation5%17%14%11%
Vomiting2%8%11%13%
Abdominal pain5%9%9%10%
Dyspepsia4%9%9%10%
Injection site reactions2%6%8%8%
Fatigue3%5%6%7%
Hypersensitivity reactions3%5%5%5%
Eructation (burping)1%4%5%5%
Hair loss1%5%4%5%
Gastroesophageal reflux2%4%4%5%

Percentages are of participants reporting the reaction at least once, not of doses. They are not a prediction about any individual.

Why the numbers do not simply rise with dose1

Constipation is highest at 5 mg and falls at higher doses; nausea is highest at 10 mg rather than 15 mg. Participants reach the higher doses only by tolerating the lower ones, so the higher-dose columns describe a group already selected for tolerating the drug. It is a real pattern in the data, not a reason to expect fewer effects from a bigger dose.

What these figures do and do not cover1

On the label — Mounjaro / Zepbound

These rates come from controlled trials of the approved product, at known doses, with an approved manufacturing process behind every injection.

In a compounded vial

No equivalent trial data exists for compounded preparations. It is reasonable to expect the drug itself to behave like the drug, but anything arising from concentration, excipients, or how a specific preparation was made is not covered by these numbers.

Serious reactions the label describes1

Beyond the common reactions above, the label describes risks including severe gastrointestinal disease, acute pancreatitis, acute gallbladder disease, acute kidney injury arising from dehydration, hypoglycemia when used alongside insulin or a sulfonylurea, hypersensitivity reactions, and diabetic retinopathy complications in people with type 2 diabetes. These are not rated by frequency here because a frequency table is the wrong tool for them — any of them is a reason to contact a prescriber rather than to consult a percentage.

Where to take this

To a prescriber. This page exists so that you know what has been reported and how often, not so that you can decide whether something you are experiencing is expected. See the medical disclaimer.

Sources

  1. FDA prescribing information for ZEPBOUND (tirzepatide), section 6.1, revision 4/2026 DailyMed