GLP-1 side effects: how common they are and how long they last

Not yet medically reviewed. Fact-checked against the sources listed below on October 7, 2026.How we write and review

Last updated October 7, 2026

The most common side effects of semaglutide and tirzepatide on their US labels are digestive: nausea, diarrhea, vomiting, constipation and abdominal pain. In the tirzepatide weight trials on the US Zepbound label, nausea affected 25% to 29% versus 8% on placebo. The label says most of these events happened while the dose was being increased.

Key takeaways

Nausea, vomiting, diarrhea, abdominal pain and constipation appear in the list of most common side effects on all four US labels: Ozempic, Wegovy, Mounjaro and Zepbound.
The US Zepbound label says most nausea, vomiting and diarrhea happened while the dose was being increased, and these events decreased over time. In STEP 1, nausea and diarrhea with semaglutide were typically short-lived and mild to moderate.
The US Wegovy and Zepbound labels carry a boxed warning: these medicines caused thyroid C-cell tumors in rodents, and it is unknown whether they do in humans.
The labels also warn about pancreatitis, gallbladder disease, low blood sugar with insulin or sulfonylureas, kidney injury from dehydration and serious allergic reactions.
Stopping because of any side effect ranged from 2.4% (STEP 4, weeks 20 to 68, versus 2.2% on placebo) to 16.6% (SELECT, mean follow-up 39.8 months, versus 8.2%) on semaglutide, and from 4.3% to 7.1% across tirzepatide doses in SURMOUNT-1 (versus 2.6%).

What are the most common side effects?

The most common side effects of semaglutide and tirzepatide are digestive. Nausea, vomiting, diarrhea, abdominal pain and constipation appear on all four US labels below.

Each label lists the side effects reported in 5% or more of patients.

Label	Medicine	Side effects reported in 5% or more
Ozempic, US label	Semaglutide	Nausea, vomiting, diarrhea, abdominal pain, constipation
Wegovy, US label	Semaglutide	Nausea, diarrhea, vomiting, constipation, abdominal pain, dysesthesia (abnormal skin sensations), headache, fatigue, indigestion, dizziness, bloating, belching, low blood sugar in people with type 2 diabetes, gas, gastroenteritis, reflux, hair loss
Mounjaro, US label	Tirzepatide	Nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion, abdominal pain
Zepbound, US label	Tirzepatide	Nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection site reactions, fatigue, allergic reactions, belching, hair loss, reflux

The Ozempic and Mounjaro labels are for type 2 diabetes. The Wegovy and Zepbound labels cover weight reduction. More about each medicine is on the semaglutide and tirzepatide pages.

How common are they?

Rates are recorded here for the Zepbound label and for several trials. Rates for each side effect on the Ozempic, Wegovy and Mounjaro labels were not recorded for this page.

Tirzepatide, US Zepbound label (weight trials)

Side effect	Tirzepatide 5 mg, 10 mg and 15 mg	Placebo
Nausea	25% to 29%	8%
Diarrhea	19% to 23%	8%
Vomiting	8% to 13%	2%
Constipation	11% to 17%	5%
Any digestive side effect (pooled Studies 1 and 2)	56% on each dose	30%

Digestive side effects in semaglutide trials

Trial	Who took part	Length	Medicine	Placebo
STEP 2	1,210 adults with type 2 diabetes and a BMI of at least 27	68 weeks	63.5% (2.4 mg), 57.5% (1.0 mg)	34.3%
STEP 3	611 adults without diabetes, with intensive behavioral therapy	68 weeks	82.8%	63.2%
STEP 4	803 adults who stayed on semaglutide or switched to placebo after a 20-week run-in	Weeks 20 to 68	49.1%	26.1%
STEP 5	304 adults without diabetes	104 weeks	82.2%	53.9%

In STEP 2 and STEP 5, these digestive side effects were mostly mild to moderate.

Other rates recorded on the US Wegovy label:

Gallstones: 1.6% on Wegovy versus 0.7% on placebo in the adult weight trials.
Gallbladder inflammation (cholecystitis): 0.6% versus 0.2%.
Heart rate: average resting heart rate rose by 1 to 4 beats per minute compared with placebo.

These figures are averages from trials. They do not predict what any one person will experience.

When do side effects happen, and how long do they last?

Digestive side effects happen mostly while the dose is being raised. In the trials recorded here, they tended to ease over time.

US Zepbound label: "The majority of nausea, vomiting, and/or diarrhea events occurred during dose escalation and decreased over time."
SURMOUNT-1 (tirzepatide): the most common side effects were digestive, mostly mild to moderate, and happened mainly during dose escalation.
SURMOUNT-1, three-year analysis: digestive side effects "occurred primarily during the dose-escalation period in the first 20 weeks of the trial."
STEP 1 (semaglutide): nausea and diarrhea were the most common side effects and were typically short-lived and mild to moderate.

This is why each label starts low and raises the dose in steps. The US Ozempic label (Revised: 05/2026), Wegovy label (Revised: 6/2026), Mounjaro label (Revised: 8/2026) and Zepbound label (Revised: 8/2026) each say their dose increase schedule is meant to reduce the risk of digestive side effects.

The Wegovy label says that if a dose is not tolerated while it is being raised, delaying the next step by 4 weeks can be considered. Your doctor sets your dose.

How many weeks a side effect lasts for one person was not recorded in the sources for this page.

What are the serious warnings?

Each US label carries warnings beyond the common side effects. The label each warning comes from is named.

Thyroid tumors (boxed warning, Wegovy and Zepbound labels): semaglutide and tirzepatide caused thyroid C-cell tumors in rodents. It is unknown whether they cause these tumors, including medullary thyroid carcinoma (MTC), in humans.
Pancreatitis (Wegovy and Zepbound labels): acute pancreatitis, including fatal and non-fatal cases, has been seen in patients treated with GLP-1 receptor agonists or tirzepatide.
Gallbladder disease (Wegovy and Zepbound labels): these medicines are associated with more cases of gallbladder disease.
Low blood sugar (Wegovy and Mounjaro labels): people who also take insulin or a sulfonylurea may have a higher risk of low blood sugar, including severe episodes.
Kidney injury (Wegovy and Zepbound labels): dehydration from side effects such as vomiting or diarrhea can lead to acute kidney injury. The Wegovy label notes postmarketing reports, some needing dialysis.
Severe digestive reactions (Ozempic label): digestive side effects are sometimes severe. Ozempic is not recommended for people with severe gastroparesis (very slow stomach emptying). The Zepbound label says the same for tirzepatide.
Diabetic eye disease (Wegovy and Zepbound labels): the Wegovy label says diabetic retinopathy complications have been reported in semaglutide trials. In SUSTAIN-6, a trial in 3,297 people with type 2 diabetes, retinopathy complications were more frequent with semaglutide than placebo (hazard ratio 1.76). The Zepbound label says temporary worsening of diabetic retinopathy has been reported with rapid improvement in blood sugar.
Serious allergic reactions (Ozempic and Zepbound labels): reactions such as anaphylaxis and angioedema have been reported.
Surgery and sedation (Ozempic and Zepbound labels): pulmonary aspiration has been reported in patients on GLP-1 receptor agonists having general anesthesia or deep sedation.
Other medicines taken by mouth (Ozempic and Zepbound labels): the Ozempic label says semaglutide slows stomach emptying and may affect how oral medicines are absorbed. The Zepbound label says tirzepatide may make birth control pills work less well.

Who should not use them?

The US labels name groups who must not use these medicines, or for whom they are not recommended.

Group	What the label says	Label
Personal or family history of medullary thyroid carcinoma, or MEN 2	Must not use	Wegovy, Zepbound
Prior serious allergic reaction to semaglutide or any ingredient	Must not use	Wegovy
Severe gastroparesis	Not recommended	Ozempic, Zepbound
Pregnancy	May harm an unborn baby. Wegovy: stop at least 2 months before a planned pregnancy. Zepbound: stop when a pregnancy is recognized	Wegovy, Zepbound
Using another GLP-1 medicine at the same time	Wegovy with other semaglutide products or any other GLP-1 receptor agonist is not recommended. The US FDA says Zepbound should not be used with Mounjaro or a GLP-1 receptor agonist	Wegovy label, US FDA

How many people stopped treatment because of side effects?

In most trials recorded here, fewer than 1 in 10 people stopped because of side effects. The longest trial, SELECT, had higher rates in both groups.

Trial	Medicine	What was counted	Medicine group	Placebo
STEP 1 (68 weeks)	Semaglutide 2.4 mg	Stopped because of digestive side effects	4.5%	0.8%
STEP 3 (68 weeks)	Semaglutide 2.4 mg	Stopped because of digestive side effects	3.4%	0%
STEP 4 (weeks 20 to 68)	Semaglutide 2.4 mg	Stopped because of any side effect	2.4%	2.2%
SELECT (mean follow-up 39.8 months)	Semaglutide 2.4 mg	Stopped permanently because of any side effect	16.6%	8.2%
SURMOUNT-1 (72 weeks)	Tirzepatide 5 mg, 10 mg, 15 mg	Stopped because of any side effect	4.3%, 7.1%, 6.2%	2.6%
SURMOUNT-2 (72 weeks)	Tirzepatide 10 mg, 15 mg	Digestive side effects leading to stopping	Fewer than 5%	Not recorded
SUMMIT (median follow-up 104 weeks)	Tirzepatide up to 15 mg	Stopped because of side effects, mainly digestive	6.3%	1.4%

SELECT was a heart outcome trial in 17,604 people aged 45 or older with cardiovascular disease. SUMMIT was a trial in 731 people with heart failure with preserved ejection fraction and obesity. In SURPASS-CVOT, which compared tirzepatide with dulaglutide in people with type 2 diabetes and atherosclerotic cardiovascular disease, more digestive side effects were seen with tirzepatide.

When should you talk to your doctor?

The US labels name several situations to raise with your doctor. This list uses only the label wording recorded for this page, and it is not a full list of symptoms.

Suspected pancreatitis: the Wegovy label says to stop Wegovy if pancreatitis is suspected.
Vomiting or diarrhea that could cause dehydration: the Wegovy and Zepbound labels say kidney function should be monitored in patients whose side effects could lead to dehydration. The Zepbound label adds that this applies especially when starting treatment.
A history of diabetic retinopathy: the Wegovy label says these patients should be monitored for progression.
Diabetes: the Wegovy label says to monitor blood sugar before starting and during treatment in patients with diabetes.
Insulin or a sulfonylurea: the Wegovy label says to consider lowering the dose of these medicines when semaglutide is started.
Planned surgery or procedure: the Ozempic label says patients should tell their healthcare providers about any planned surgery or procedure.
Pregnancy or planning one: the Wegovy label says to stop at least 2 months before a planned pregnancy. The Zepbound label says to stop when a pregnancy is recognized.
Birth control pills: the Zepbound label advises switching to a non-oral method, or adding a barrier method, for 4 weeks after starting tirzepatide and for 4 weeks after each dose increase.

Frequently asked questions

What are the most common side effects of semaglutide?

The US Ozempic label lists nausea, vomiting, diarrhea, abdominal pain and constipation as the side effects reported in 5% or more of patients. The US Wegovy label lists these and others, including headache, fatigue, dizziness, bloating, belching, reflux and hair loss.

What are the most common side effects of tirzepatide?

The US Mounjaro label lists nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion and abdominal pain. The US Zepbound label adds injection site reactions, fatigue, allergic reactions, belching, hair loss and reflux. In the Zepbound weight trials, nausea affected 25% to 29% of people on tirzepatide versus 8% on placebo.

How long do GLP-1 side effects last?

The US Zepbound label says most nausea, vomiting and diarrhea happened while the dose was being increased, and these events decreased over time. In a three-year SURMOUNT-1 analysis, digestive side effects happened mainly during the dose increase period in the first 20 weeks. In STEP 1, nausea and diarrhea with semaglutide were typically short-lived.

Are side effects worse when the dose goes up?

The US Ozempic, Wegovy, Mounjaro and Zepbound labels all start at a low dose and raise it step by step to reduce the risk of digestive side effects. The Zepbound label says most nausea, vomiting and diarrhea happened during this dose increase. Your doctor sets your dose.

Do semaglutide and tirzepatide cause hair loss?

Hair loss is listed among the side effects reported in 5% or more of patients on the US Wegovy and Zepbound labels. How often it happened was not recorded for this page.

Can GLP-1 medicines cause pancreatitis?

The US Wegovy and Zepbound labels warn about it. The US Wegovy and Zepbound labels say acute pancreatitis, including fatal cases, has been seen in patients treated with GLP-1 receptor agonists or tirzepatide. The Wegovy label says to stop Wegovy if pancreatitis is suspected.

Do GLP-1 medicines cause thyroid cancer?

It is not known. The US Wegovy and Zepbound labels carry a boxed warning that semaglutide and tirzepatide caused thyroid C-cell tumors in rodents, and that it is unknown whether they cause these tumors, including medullary thyroid carcinoma, in humans. Both labels say people with a personal or family history of medullary thyroid carcinoma or MEN 2 must not use them.

How many people stop GLP-1 medicines because of side effects?

It depends on the trial. In STEP 1, 4.5% stopped semaglutide because of digestive side effects versus 0.8% on placebo. In SURMOUNT-1, 4.3% to 7.1% stopped tirzepatide because of side effects versus 2.6% on placebo.

Can GLP-1 medicines cause low blood sugar?

The US Wegovy and Mounjaro labels say people who also take insulin or a sulfonylurea may have a higher risk of low blood sugar, including severe episodes. The Wegovy label says to consider lowering the insulin or sulfonylurea dose when semaglutide is started.

Can I use a GLP-1 medicine during pregnancy?

The US Wegovy and Zepbound labels say these medicines may harm an unborn baby. The Wegovy label says to stop at least 2 months before a planned pregnancy, because semaglutide stays in the body a long time. The Zepbound label says to stop when a pregnancy is recognized.

Do GLP-1 medicines affect birth control pills?

The US Zepbound label says tirzepatide may make birth control pills work less well. It advises switching to a non-oral method, or adding a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase.

Should I tell my doctor about GLP-1 medicines before surgery?

Yes. The US Ozempic label says pulmonary aspiration has been reported in patients on GLP-1 receptor agonists having general anesthesia or deep sedation, and that patients should tell their healthcare providers about any planned surgery or procedure.

Sources

This content is for education only and is not medical advice. Talk to a licensed doctor before starting any treatment.