Tirzepatide Side Effects (What the FDA Label Lists)

By DoseGauge Editorial · Updated 2026-06-12 · 6 min read

According to the FDA labels for tirzepatide (Mounjaro and Zepbound), the most common side effects are gastrointestinal: nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain. The labels also carry a boxed warning about thyroid C-cell tumors seen in rats, contraindications in people with certain thyroid cancer history, and several other warnings. Everything below is taken from those labels. It is information, not medical advice, and it is not a complete list of every reaction in the label.

Common side effects

The tirzepatide labels list these as the most common adverse reactions (reported in at least 5% of patients):

• Nausea
• Diarrhea
• Decreased appetite
• Vomiting
• Constipation
• Dyspepsia (indigestion)
• Abdominal pain

The label notes that gastrointestinal reactions are the most frequently reported and that they were generally most common during dose escalation. That escalation pattern is the reason the labeled dosing starts low and steps up slowly.

Two things are worth stating plainly about this list. First, it is the set of reactions reported in at least 5% of patients in the trials, so it is the common-frequency tier, not the full catalog. The label's adverse-reaction tables contain additional, less frequent reactions. Second, the list is descriptive: it records what was reported, at what rate, in the studied populations. It does not predict whether a given person will have any of these reactions or how severe they would be.

Serious warnings and the boxed warning

The label opens with a boxed warning, the FDA's most prominent warning format. Its wording: tirzepatide causes thyroid C-cell tumors in rats, and it is unknown whether tirzepatide causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, because the human relevance of the rodent finding has not been determined.

Tied to that warning, the label lists two contraindications:

• A personal or family history of medullary thyroid carcinoma, or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
• A known serious hypersensitivity to tirzepatide or any of its excipients.

Other warnings and precautions

The label's Warnings and Precautions section covers several distinct risks. Each is attributed to the label, not to any judgment on this page:

• Acute pancreatitis. Pancreatitis has been observed in patients treated with tirzepatide.
• Hypoglycemia with concomitant use of insulin secretagogues or insulin. The risk of low blood sugar rises when tirzepatide is combined with these.
• Hypersensitivity reactions. Serious reactions have been reported.
• Acute kidney injury due to volume depletion. Gastrointestinal effects can cause dehydration, which has been linked to kidney injury.
• Severe gastrointestinal adverse reactions. Beyond the common mild-to-moderate effects, the label flags severe gastrointestinal reactions.
• Diabetic retinopathy complications in patients with a history of diabetic retinopathy.
• Acute gallbladder disease.
• Pulmonary aspiration during general anesthesia or deep sedation, related to delayed gastric emptying.

This list reflects the section headings in the label. The label itself contains the full detail and the complete adverse-reaction tables.

The label pairs several of these warnings with concrete instructions to clinicians, such as discontinuing the drug if pancreatitis is suspected, monitoring kidney function when severe gastrointestinal reactions cause volume depletion, and counseling patients on the symptoms of gallbladder disease. Those instructions are directed at prescribers and are part of why the label exists. Reproducing the headings here is meant to show the scope of what the label addresses, not to interpret any item for an individual situation.

It is worth noting how the label tiers these risks, because the structure carries meaning. The boxed warning sits at the very top and addresses the thyroid C-cell tumor finding. Contraindications come next and define who should not receive the drug at all. Warnings and precautions then describe risks that call for monitoring or caution during use. Common adverse reactions, the gastrointestinal list, sit lower because they are frequent but generally milder than the items above them. Reading the label in that order separates the rare-but-serious from the common-but-milder, which is the distinction the label is built to communicate.

What this means for dosing

The labeled titration schedule, starting at 2.5 mg weekly and increasing in 2.5 mg steps no sooner than every 4 weeks, is structured to reach a maintenance dose while managing the gastrointestinal reactions that cluster around dose increases. That is the label's stated rationale for stepping up gradually rather than starting high. It is the reasoning behind the schedule, not a suggestion about what you should do.

If you are converting a labeled dose into syringe units from a reconstituted vial, the calculator does that arithmetic from your inputs. It computes; it does not advise.

FAQ

Do tirzepatide side effects go away?

The label states that gastrointestinal reactions were generally most common during dose escalation. It does not promise that any individual's side effects resolve or persist. How side effects behave over time for a specific person is a clinical question for a prescriber.

What are the most common tirzepatide side effects?

Per the label, the most common adverse reactions are nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain.

Who should not take tirzepatide?

The label contraindicates it in people with a personal or family history of medullary thyroid carcinoma or MEN 2, and in people with a known serious hypersensitivity to tirzepatide or its excipients. Eligibility beyond those contraindications is determined by a clinician.

Is the boxed warning based on human cancer cases?

No. The boxed warning is based on thyroid C-cell tumors observed in rats. The label states explicitly that it is unknown whether tirzepatide causes thyroid C-cell tumors, including medullary thyroid carcinoma, in humans, because the human relevance of the rodent finding has not been determined. The warning and the contraindication exist as a precaution around that uncertainty.

Does this page list every possible side effect?

No. This summary covers the common adverse reactions and the warnings sections from the label. The full prescribing information contains additional reactions, frequency tables, and detail that this page does not reproduce. The label is the authoritative source, and the link to it appears in the sources below.

Informational and educational only. Not medical advice. DoseGauge computes from the values you enter and does not recommend a dose. Talk to a licensed clinician before using any peptide or GLP-1 medication.