GLP-1 side effects: common, serious, and worth discussing.

Scope and education-only boundary

This guide summarizes the current U.S. Wegovy (semaglutide) and Zepbound (tirzepatide) labels, their pivotal obesity trials, and systematic evidence available through July 11, 2026. It does not diagnose symptoms or recommend starting, stopping, switching, combining, or dosing a medication.

Side effects are not one interchangeable class-wide list. Product, formulation, indication, dose, population, follow-up time, and other medicines can change the safety picture. Evidence from these approved products should not be transferred to compounded, salt-form, research-use, or other unapproved products.

Common effects in the sources we checked

In adult weight-reduction trials summarized in the current labels, both Wegovy injection and Zepbound most often involved gastrointestinal adverse reactions. The labels list nausea, diarrhea, vomiting, constipation, abdominal pain, and dyspepsia among common reactions; they also list product-specific effects such as reflux, fatigue, hair loss, and other reactions.

STEP 1 followed adults without diabetes for 68 weeks and reported nausea and diarrhea as the most common adverse events with semaglutide 2.4 mg. SURMOUNT-1 followed adults without diabetes for 72 weeks, including a 20-week dose-escalation period, and reported gastrointestinal events as the most common adverse events with tirzepatide, mostly mild to moderate and occurring mainly during escalation.

• Wegovy label trial pool: 2,116 adults receiving 2.4 mg injection for up to 68 weeks, compared with 1,261 receiving placebo.
• Zepbound label trial pool: 2,519 adults receiving 5 mg, 10 mg, or 15 mg for up to 72 weeks, compared with 958 receiving placebo.
• Rates from separate trials should not be compared as if they came from a direct head-to-head safety study.

Serious label warnings are product-specific

The current Wegovy and Zepbound labels include boxed-warning language about thyroid C-cell tumors seen in rodents and say it is unknown whether the products cause medullary thyroid carcinoma in humans. Both are contraindicated for people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2.

Both labels also carry product-specific warnings or precautions for severe gastrointestinal reactions, acute kidney injury due to volume depletion, acute gallbladder disease, acute pancreatitis, serious hypersensitivity reactions, hypoglycemia in relevant medication combinations, diabetic retinopathy considerations for people with type 2 diabetes, and pulmonary aspiration during general anesthesia or deep sedation. Pregnancy, lactation, and reproductive-potential language differs by product and should be checked in the exact current label.

What the evidence cannot answer yet

A 2026 systematic review and network meta-analysis of 262 trials in adults with overweight or obesity found increased gastrointestinal events with several medicines, including tirzepatide. Most trials were relatively short, so conclusions about long-term safety are limited. Network estimates combine different drugs, formulations, doses, trial designs, and follow-up periods, so they do not establish one person's risk or a universal safety ranking.

A separate meta-analysis of 76 randomized trials found an association between GLP-1 receptor agonist treatment and gallbladder or biliary disease across mixed adult populations. It does not isolate every current product, formulation, indication, or personal risk factor. For rare events such as pancreatitis, aspiration, severe gastroparesis-like illness, or serious hypersensitivity, this page uses current label language and does not claim a precise incidence or causal estimate beyond the cited source.

When symptoms need professional care

The current labels and MedlinePlus patient information tell readers to contact a healthcare professional promptly for severe or persistent abdominal pain, repeated vomiting or inability to keep fluids down, signs of dehydration, serious allergic-type symptoms, or other severe or rapidly worsening symptoms. Breathing difficulty, facial or throat swelling, fainting, or symptoms that feel like an emergency call for emergency care rather than online research.

This summary cannot tell whether a symptom is medication-related. The exact product's patient information and a licensed clinician who knows the person's health history are the appropriate sources for an individual situation.

Questions to discuss with a licensed clinician

Questions keep this guide on the education side of the medical boundary:

• Which exact product, formulation, indication, and current label apply to me?
• Which warnings or contraindications matter for my health history, pregnancy plans, current medicines, or upcoming anesthesia or sedation?
• Which symptoms should prompt a same-day call, urgent evaluation, or emergency care?
• How would vomiting, diarrhea, or reduced intake affect hydration, kidney risk, blood sugar, or other medicines in my situation?

How The Glow Diary handles safety

We do not use side-effect pages to scare readers, rank products, or sell alternatives. We keep claims tied to exact labels, study populations, timeframes, and limitations, and we turn remaining uncertainty into questions for qualified healthcare professionals.

Sources and further reading

These links are included to make the evidence trail visible. They are not sponsor links and do not replace product-specific medical advice.