Common side effects: what each label says

The most common side effects, by medicine

From the Highlights section of each prescribing information.^{[1, 2, 3, 4]} The lists differ partly because each medicine was studied in different trials and for different uses, so they are not a head-to-head comparison.

Stomach side effects

Nausea, diarrhea, vomiting, constipation and abdominal pain appear on the most common list for all four medicines.^{[1, 2, 3, 4]} Every label also has a warning about severe gastrointestinal side effects, so stomach symptoms that are severe or will not settle are worth a call to your prescriber.^{[1, 2, 3, 4]}

Fluids matter. The labels warn that losing fluids through vomiting or diarrhea can lead to dehydration and kidney problems.^{[8, 6]} Lilly suggests drinking plenty of fluids if you have diarrhea, and names water as the preferred choice.^[5]

What the manufacturers suggest

Both manufacturers publish simple tips for the most common stomach side effects:

For nausea

• Split three meals into four or more smaller ones, and stop eating when you feel full.^[5]
• Eat more slowly.^{[6, 7]}
• Choose bland, low-fat foods such as toast, crackers or rice, and foods that contain water, such as soup.^{[5, 6, 7]}
• Avoid fatty, fried or greasy foods.^{[5, 7]}
• Avoid lying down right after eating, and get some fresh air.^[6]

For diarrhea

• Drink plenty of clear fluids to stay hydrated.^[5]
• Limit dairy, and try bland foods such as broth, rice or carrots.^[5]

These are general tips from the manufacturers, not treatment. If a side effect bothers you or does not go away, Lilly's advice is to talk to your doctor.^[5]

Other common side effects

• Injection site reactions are on the Zepbound list.^[1] Rotating sites each week is part of every label's instructions, and the logbook helps you keep track.
• Fatigue is on the Zepbound and Wegovy lists.^{[1, 3]}
• Hair loss is on the Zepbound and Wegovy lists.^{[1, 3]}
• Belching and reflux are on the Zepbound and Wegovy lists.^{[1, 3]}
• Headache and dizziness are on the Wegovy list.^[3]
• Decreased appetite is on the Mounjaro list.^[2]

When to call your prescriber

Call your prescriber if:

• a side effect bothers you or does not go away;^[5]
• vomiting or diarrhea means you cannot keep fluids down;
• you have any of the symptoms on the warning signs page. Some of them, such as severe stomach pain that will not go away or signs of a serious allergic reaction, mean stopping the medicine and getting help right away.

You can also report side effects to the FDA at 1-800-FDA-1088.^[8]

Common questions