GLP-1 side effects: how common they are and what helps

Stomach and bowel problems top every GLP-1 side-effect table, led by nausea. In label trials, nausea affected 44% of people on Wegovy 2.4 mg (vs 16% on placebo), 25% to 29% on Zepbound (vs 8%) and 26% to 35% on Foundayo (vs 10%). The general steps that help are eating smaller meals, stopping when you feel full, staying hydrated and talking to your clinician about how fast your dose goes up.

How to read the numbers

Each rate below comes from the drug’s FDA label, which compares people on the drug with people on a placebo (an inactive shot or pill) in the same trials. Placebo groups report nausea too, so the useful number is the gap. On Zepbound 15 mg, 28% had nausea vs 8% on placebo: about 20 extra people in every 100.

Each drug was tested in its own trials, with its own doses and patients. A lower number on one label is not a head-to-head result, so compare across columns with care.

Side-effect rates by drug

Percent of patients, drug vs placebo. “n/a” means that label’s table does not list it.

Scroll sideways to see the full table

Sources: Wegovy label Tables 3 and 4 (rev. 06/2026); Zepbound label weight-trial pool (rev. 08/2026); Foundayo label pooled Trials 1 and 2 (rev. 07/2026); Saxenda label Table 2 (rev. 02/2026).

Stomach and bowel side effects

Nausea leads every column, and diarrhea, vomiting and constipation are the other frequent ones. A few patterns stand out:

• On Zepbound, vomiting rose with dose (8%, 11% and 13% vs 2%), while constipation fell (17%, 14% and 11% vs 5%).
• On Foundayo, the daily pill, vomiting climbed from 13% at 5.5 mg to 24% at 17.2 mg, vs 4% on placebo.
• Indigestion (dyspepsia) ran 9% to 16% across the drugs, vs 4% or less on placebo.

Mounjaro, which is tirzepatide approved for type 2 diabetes, lists lower rates on its label: nausea in 12% to 18% vs 4% on placebo, and diarrhea in 12% to 17% vs 9% (Mounjaro label, rev. 08/2026). Ozempic’s label names nausea, vomiting, diarrhea, abdominal pain and constipation as its most common side effects, each in 5% or more of patients (Ozempic label, rev. 05/2026).

The Wegovy pill shares a label with the injection. It says the types and rates of common side effects were similar, and that side effects led 6.9% of pill users to stop, vs 5.9% on placebo.

Other common side effects

Headache, fatigue and hair loss show up at lower rates. Fatigue ran 5% to 11% across the drugs, vs 3% to 5% on placebo. Headache barely differed from placebo on Saxenda (13.6% vs 12.6%).

Hair loss stayed in single digits: 3% on Wegovy 2.4 mg vs 1% on placebo, 6% at 7.2 mg, and 4% to 5% on Zepbound and Foundayo.

The 7.2 mg dose of Wegovy, sold as Wegovy HD, added one less familiar effect. Dysesthesia, which the label describes as skin sensitivity, affected 22% of people at 7.2 mg vs 0% on placebo. At 2.4 mg it was 2% vs 1%. If you are weighing the higher dose, ask your clinician about it.

Injection-site reactions affected 6% to 8% of people on Zepbound vs 2% on placebo, and 13.9% on Saxenda vs 10.5%. Pills such as Foundayo have no injection site.

Serious risks on the labels

Beyond the common side effects, the labels carry warnings worth reading before you start.

Every product in this comparison, plus Ozempic, Rybelsus and Mounjaro, carries a boxed warning for thyroid C-cell tumors. None of them is for people with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Foundayo’s orforglipron is not active in rats or mice and caused no tumors in rodents, yet its label carries the same warning.

The Wegovy label’s other warnings include:

• Pancreatitis and gallbladder disease.
• Low blood sugar when used with insulin or a sulfonylurea.
• Acute kidney injury from dehydration.
• Severe stomach and bowel reactions. It is not recommended in severe gastroparesis.
• A risk of breathing stomach contents into the lungs (aspiration) under anesthesia.

Tell your clinician about your medical history and other medicines before you start, and tell anyone planning a procedure with anesthesia that you take a GLP-1.

What helps

These steps are general. They do not replace advice from the clinician who prescribes your medication.

Eat smaller meals

Smaller portions are a simple first change if you feel queasy or uncomfortably full after eating.

Stop eating when you feel full

Stop when you feel full, even if your plate is not empty.

Stay hydrated

Vomiting and diarrhea can leave you short on fluids, and the labels warn about acute kidney injury linked to dehydration. Drink fluids through the day, and call your clinician if you cannot keep fluids down.

Talk to your clinician about dose pace

The labels raise doses in steps. Zepbound starts at 2.5 mg for 4 weeks, then moves up in 2.5 mg steps at least 4 weeks apart. Wegovy injection steps up every 4 weeks for 16 weeks, and its label allows 1.7 mg or 2.4 mg as a maintenance dose. Foundayo needs at least 30 days at each dose. If the 25 mg Wegovy pill is not tolerated, the label suggests switching to the 1.7 mg weekly injection.

If side effects are hard to live with, ask whether staying longer at your current dose, or a lower maintenance dose, fits your case. Do not change your dose on your own.

A note on compounded GLP-1s

The rates above come from trials of FDA-approved products. Compounded semaglutide and tirzepatide are not those products, and not generics of them. A compounding pharmacy prepares them, they aren’t FDA-approved, and the FDA does not review compounded drugs for safety, effectiveness or quality before they are sold (FDA, 2026). These tables do not describe them. Our guide to compounded semaglutide’s legal status and safety has more.

The bottom line

Most GLP-1 side effects in label trials involve the stomach and bowel, with nausea at the top: 25% to 44% on the main weight-loss drugs vs 8% to 16% on placebo. Smaller meals, stopping when full, steady fluids and an honest talk with your clinician about dose pace are the general steps that help. Read the boxed warning and the other label warnings before you start, and call your clinician if side effects are severe or keep you from eating or drinking. When you are ready to compare programs, our match tool can help.