GLP-1 side effects

Side effect rates by brand

Common side effects in FDA label trials: drug rate (placebo rate)

Brand, dose and trial group	Nausea	Diarrhea	Vomiting	Constipation	Stomach pain	Stopped for side effects	Brand page
Zepbound 5 to 15 mg, weight trials [1]	25% to 29% (8%)	19% to 23% (8%)	8% to 13% (2%)	11% to 17% (5%)	9% to 10% (5%)	4.8% to 6.7% (3.4%)	Zepbound side effects
Mounjaro 5 to 15 mg, type 2 diabetes trials [6]	12% to 18% (4%)	12% to 17% (9%)	5% to 9% (2%)	6% to 7% (1%)	5% to 6% (4%)	Not in our label review	Mounjaro side effects
Wegovy 2.4 mg shot, adult weight trials [2]	44% (16%)	30% (16%)	24% (6%)	24% (11%)	20% (10%)	6.8% (3.2%)	Wegovy side effects
Wegovy 7.2 mg shot [2]	39% (13%)	Not in our label review	22% (6%)	20% (8%)	Not in our label review	5% (2%)	Wegovy side effects
Wegovy pill 25 mg [2]	Similar to the 2.4 mg shot	Similar to the 2.4 mg shot	Similar to the 2.4 mg shot	Similar to the 2.4 mg shot	Similar to the 2.4 mg shot	6.9% (5.9%)	Wegovy pill
Ozempic 0.5 to 1 mg, type 2 diabetes trials [7]	15.8% to 20.3% (6.1%)	8.5% to 8.8% (1.9%)	5.0% to 9.2% (2.3%)	3.1% to 5.0% (1.5%)	5.7% to 7.3% (4.6%)	Not in our label review	Ozempic side effects
Foundayo 5.5 to 17.2 mg, pooled trials [4]	26% to 35% (10%)	21% to 25% (11%)	13% to 24% (4%)	20% to 27% (9%)	13% to 14% (7%)	6% to 10% (3%)	Foundayo

For drug-level detail, see tirzepatide side effects and semaglutide side effects.

Other common effects on the labels

• Zepbound: indigestion 9% to 10% (placebo 4%), injection site reactions 6% to 8% (2%), fatigue 5% to 7% (3%), allergic-type reactions 5% (3%), burping 4% to 5% (1%), hair loss 4% to 5% (1%) and reflux 4% to 5% (2%) ^[1].
• Wegovy 2.4 mg: headache 14% (10%), fatigue 11% (5%), indigestion 9% (3%) and dizziness 8% (4%) ^[2].
• Wegovy 7.2 mg: dysesthesia, an altered sense of touch on the skin, in 22% vs 6% on 2.4 mg and 0% on placebo; hair loss 6% vs 3% and 1% ^[2]. The Wegovy pill showed dysesthesia in 5% vs 0% ^[2].
• Mounjaro: decreased appetite 5% to 11% (1%) ^[6].
• Foundayo: indigestion 12% to 16% (4%) ^[4].

When side effects start and how long they last

In SURMOUNT-1, most stomach effects on tirzepatide were mild to moderate and happened mainly during dose escalation ^[3]. In STEP 1, nausea and diarrhea on semaglutide were typically short-lived and mild to moderate, and 4.5% stopped because of stomach effects vs 0.8% on placebo ^[8]. If a Wegovy dose step is not tolerated, the label lets the prescriber consider delaying the next step by 4 weeks ^[2]. See Wegovy dosage and tirzepatide dosage.

Serious warnings on the labels

Warnings and precautions on the Zepbound and Wegovy labels

Warning	What the label says	Source
Thyroid C-cell tumors (boxed warning)	Caused tumors in rodents; human risk unknown. Do not use with a personal or family history of medullary thyroid carcinoma (MTC) or MEN 2. Foundayo carries the same class warning.	[1][2][4]
Acute pancreatitis	Stop the drug if pancreatitis is suspected	[1][2]
Acute gallbladder disease	Listed on both labels	[1][2]
Acute kidney injury	Can follow fluid loss from vomiting or diarrhea	[1][2]
Severe stomach and gut reactions	Zepbound is not recommended in severe gastroparesis	[1][2]
Low blood sugar	Higher risk with insulin or a sulfonylurea	[1][2]
Allergic reactions	Including anaphylaxis and angioedema	[1][2]
Diabetic eye disease (retinopathy)	Complications reported in people with type 2 diabetes	[5][2]
Heart rate increase	Listed on the Wegovy label	[2]
Breathing in stomach contents under anesthesia	Tell the care team you take the drug before any planned procedure	[1][2]

The suicidal behavior and ideation warning was removed from the Zepbound and Wegovy labels in February 2026 ^[5]. For Foundayo, FDA required 5 years of enhanced monitoring for drug-induced liver injury as a condition of approval ^[9].

Pregnancy, breastfeeding and birth control

• Stop Zepbound or Wegovy when pregnancy is recognized; weight loss offers no benefit in pregnancy and may harm the fetus ^[1][2].
• Stop semaglutide at least 2 months before a planned pregnancy because it stays in the body a long time ^[2].
• Mounjaro and Ozempic labels say to use them in pregnancy only if the benefit justifies the risk to the fetus ^[6][7].
• Breastfeeding is not recommended on the Wegovy pill or Foundayo ^[2][4].
• Tirzepatide can make birth control pills less effective: use a non-oral method or add a barrier method for 4 weeks after starting and after each dose increase ^[6]. Foundayo's label says 30 days ^[4].

Compounded and unapproved GLP-1s

Compounded semaglutide and tirzepatide are not FDA-approved, and FDA does not review them for safety, effectiveness or quality ^[11]. FDA had received 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide as of May 31, 2026, and says these are likely undercounted ^[10]. It also reports dosing errors with compounded injections, some needing hospital care ^[10]. Products sold as research use only have unknown quality and may be harmful ^[10]. See compounded semaglutide, compounded tirzepatide, research-use-only GLP-1s and our FDA warning letter tracker.