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Side effects

Semaglutide side effects

Semaglutide side effects are mostly digestive: in Wegovy trials, nausea affected 44% of people vs 16% on placebo.1 The labels also carry a boxed warning about thyroid C-cell tumors seen in rodents and list rarer serious risks, including pancreatitis, gallbladder disease and kidney injury from fluid loss.2345

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Where these numbers come from

Most figures below come from the FDA labels, which report placebo-controlled trials of the approved medicines.16 Wegovy figures are for the 2.4 mg weekly dose unless noted, and Ozempic figures are for 0.5 mg and 1 mg weekly in people with type 2 diabetes.16 These data do not cover research-labeled semaglutide; FDA says unapproved versions of GLP-1 drugs do not undergo its review for safety, effectiveness and quality.15

Most common: digestive effects

Side effect Wegovy 2.4 mg1 Placebo Ozempic 0.5 mg and 1 mg6 Placebo
Nausea 44% 16% 15.8% and 20.3% 6.1%
Diarrhea 30% 16% 8.5% and 8.8% 1.9%
Vomiting 24% 6% 5% and 9.2% 2.3%
Constipation 24% 11% 5% and 3.1% 1.5%
Abdominal pain 20% 10% 7.3% and 5.7% 4.6%

The labels raise the dose in steps of at least 4 weeks specifically to reduce these effects; the schedules are on Semaglutide dosage.1011

Other common effects

  • Headache in 14% vs 10% on placebo, and fatigue in 11% vs 5%, with Wegovy 2.4 mg.1
  • Also listed at 5% or more on the Wegovy label: dizziness, indigestion (dyspepsia), bloating, burping, gas, gastroenteritis, acid reflux (GERD) and unusual skin sensations (dysesthesia).1
  • Dysesthesia rises sharply at the top dose: 22% with Wegovy 7.2 mg vs 6% with 2.4 mg and 0.3% with placebo.16
  • Low blood sugar in people with type 2 diabetes: clinically significant episodes (below 54 mg/dL) in 6.2% vs 2.5% in a Wegovy trial, with a higher risk when combined with insulin or insulin secretagogues.49
  • Faster resting heart rate: average rises of 1 to 4 beats per minute with Wegovy and 2 to 3 with Ozempic.46 The Wegovy label advises checking heart rate at regular intervals.4
  • Raised pancreatic enzymes: average increases of 13% in amylase and 22% in lipase with Ozempic.6
  • Injection-site reactions such as discomfort or redness in 0.2% of Ozempic-treated patients.6

Less common but serious

  • Gallbladder: gallstones (cholelithiasis) in 1.6% vs 0.7% on placebo, and gallbladder inflammation (cholecystitis) in 0.6% vs 0.2%, with Wegovy injection.4
  • Acute pancreatitis: 4 Wegovy-treated patients (0.2 cases per 100 patient-years) vs 1 on placebo.3 Reports after approval include necrotizing pancreatitis, sometimes fatal, and the labels say to stop the drug if pancreatitis is suspected.39
  • Acute kidney injury: 7 Wegovy-treated adults (0.4 cases per 100 patient-years) vs 4 on placebo.5 The labels link it to fluid loss from vomiting or diarrhea and advise monitoring kidney function in that situation.5
  • Diabetic eye disease: retinopathy complications in 3.0% vs 1.8% in a 2-year Ozempic trial, and 4% vs 2.7% in a Wegovy trial in type 2 diabetes.84 Patients with a history of retinopathy should be monitored.8
  • NAION: in large epidemiological studies reviewed by the EU safety committee, adults with type 2 diabetes taking semaglutide had about a two-fold higher risk. The committee judged it very rare, up to 1 in 10,000 users, and said treatment is stopped if NAION is confirmed.12
  • Reports after approval: bowel blockage (ileus, intestinal obstruction), severe constipation with fecal impaction, serious allergic reactions (anaphylaxis, angioedema), rash and hives.3 Food or liquid can also enter the lungs (pulmonary aspiration) under general anesthesia or deep sedation, so patients are told to mention planned procedures.3

Boxed warning and who should not use it

Semaglutide caused thyroid C-cell tumors in rodents at clinically relevant exposures, and it is unknown whether it causes them in people, including medullary thyroid carcinoma (MTC).132 It must not be used with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), or after a serious allergic reaction to semaglutide.13 The labels list three further limits:

  • Pregnancy: the Wegovy label says semaglutide may cause fetal harm and is stopped when pregnancy is recognized in people using it for weight or heart risk. For MASH, and in the Ozempic label, it is used in pregnancy only if the benefit justifies the risk to the fetus. Both labels advise stopping at least 2 months before a planned pregnancy.59
  • Stomach emptying: Ozempic is not recommended in severe gastroparesis, and gastrointestinal reactions can be severe.8
  • Other GLP-1 drugs: Wegovy is not recommended with other semaglutide products or other GLP-1 receptor agonists.14

How many people stop because of side effects

In Wegovy injection trials, 6.8% stopped because of an adverse reaction vs 3.2% on placebo.16 In SELECT, which followed 17,604 adults for a mean of 39.8 months, adverse events led 16.6% to stop permanently vs 8.2% on placebo.17

Suicidal thoughts: what FDA found

A January 2026 FDA meta-analysis of 91 placebo-controlled GLP-1 drug trials with 107,910 patients found no increased risk of suicidal thoughts or behavior.18 FDA then asked makers to remove that warning, and the current Wegovy label lists it as removed in February 2026.1814

Compounded and unapproved products

FDA had received 990 adverse event reports linked to compounded semaglutide as of May 31, 2026.19 Dosing errors with compounded vials, some of 5 to 20 times the intended amount, were followed by nausea, vomiting, abdominal pain, fainting, headache, migraine, dehydration, acute pancreatitis and gallstones.20 Some people needed hospital care.19 FDA also warns that counterfeit Ozempic found in the US supply chain could contain the wrong ingredients, too much or too little active ingredient, or none at all.2122

Back to What is Semaglutide?. Results that these risks are weighed against are on Semaglutide benefits and uses, and vial handling is on How to reconstitute Semaglutide. Class-wide effects: GLP-1 side effects.

More on Semaglutide

  • Semaglutide dosage

    Published dosing information for Semaglutide from labels and studies, with its source, and why it is not advice for you.

  • Semaglutide benefits and uses

    What published sources report about Semaglutide and its uses, with the evidence level of each finding. No promises.

  • How to reconstitute Semaglutide

    How Semaglutide is reconstituted, the supplies used, and the calculator, step by step. Sourced and reviewed.

Frequently asked questions

What are the potential side effects of taking semaglutide?

The most common are digestive: nausea, diarrhea, vomiting, constipation and abdominal pain, each more frequent than on placebo in label trials.16 Headache, fatigue, dizziness and hair loss are also listed.17 Less common but serious risks include pancreatitis, gallbladder disease, kidney injury from dehydration, worsening diabetic eye disease, and low blood sugar when it is combined with insulin.34589

How to manage side effects of semaglutide?

The labels build some management into treatment. The dose rises in steps of at least 4 weeks specifically to reduce gastrointestinal side effects.1011 Kidney function is monitored in people with vomiting or diarrhea that could cause dehydration, and the drug is stopped if pancreatitis is suspected.59 The EU safety committee advises anyone with sudden vision loss to contact a doctor without delay.12 Any change to treatment is the prescriber's decision.

Who should avoid semaglutide?

The labels say not to use it with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).13 The same applies after a serious allergic reaction to semaglutide or one of its ingredients.13 It is stopped at least 2 months before a planned pregnancy, is not recommended in severe gastroparesis, and is not combined with other semaglutide products or other GLP-1 receptor agonists.5814

Does semaglutide cause hair loss?

Hair loss is a listed side effect. In Wegovy trials it was reported by 3.3% of patients on 2.4 mg (4% of women, 0.9% of men) vs 1% on placebo, and by 5.8% of patients on the 7.2 mg dose.7 The label links these reports to weight reduction.7 For scale, the most common side effect at 2.4 mg, nausea, affected 44% of patients.1

Can semaglutide affect your eyesight?

Two eye issues are on record. In a 2-year diabetes trial, diabetic retinopathy complications occurred in 3.0% on Ozempic vs 1.8% on placebo, and a rapid improvement in blood sugar can temporarily worsen retinopathy.8 In June 2025 the EU safety committee concluded that NAION, an optic nerve condition, is a very rare side effect, affecting up to 1 in 10,000 people taking semaglutide.12

Written by D2C Peptides Editorial Team.

Pending qualified review.

Updated .

Sources

  1. WEGOVY (semaglutide) prescribing information, Highlights: most common adverse reactions; section 6.1 Table 3. DailyMed, U.S. National Library of Medicine (Novo Nordisk label, revised 6/2026), 2026.
  2. OZEMPIC (semaglutide) injection prescribing information, Boxed Warning. DailyMed, U.S. National Library of Medicine (Novo Nordisk label, revised 5/2026), 2026.
  3. Same source as 1: Warnings (pulmonary aspiration) and section 6.2 Postmarketing Experience.
  4. Same source as 1: section 5 Warnings and Precautions (gallbladder, heart rate).
  5. Same source as 1: Use in Specific Populations; Warnings (acute kidney injury).
  6. Same source as 2: section 6 Adverse Reactions.
  7. Same source as 1: section 6.1 (hair loss).
  8. Same source as 2: Warnings and Precautions (diabetic retinopathy, gastrointestinal).
  9. Same source as 2: Warnings (pancreatitis, hypoglycemia) and Use in Specific Populations.
  10. Same source as 2: section 2 Dosage and Administration.
  11. Same source as 1: WEGOVY (semaglutide) injection and tablets prescribing information, section 2 Dosage and Administration.
  12. PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines Ozempic, Rybelsus and Wegovy. European Medicines Agency (news, 6 June 2025), 2025.
  13. Same source as 1: Boxed Warning and Contraindications.
  14. Same source as 1: WEGOVY (semaglutide) injection and tablets prescribing information, section 1 Indications and Usage.
  15. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (compounded drugs). U.S. Food and Drug Administration (content current as of 10/01/2026), 2026.
  16. Same source as 1: section 6.1 (dysesthesia, discontinuations).
  17. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT; Lincoff et al.), PubMed abstract PMID 37952131. New England Journal of Medicine (abstract via NLM PubMed E-utilities), 2023.
  18. FDA Requests Removal of Suicidal Behavior and Ideation Warning from Glucagon-Like Peptide-1 Receptor Agonist (GLP-1 RA) Medications. U.S. Food and Drug Administration (Drug Safety Communication, January 13, 2026), 2026.
  19. Same source as 15: FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (adverse event reports, dosing errors).
  20. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products. U.S. Food and Drug Administration (content current as of 07/26/2024), 2024.
  21. Same source as 15: FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (research-labeled and counterfeit products).
  22. FDA warns consumers not to use counterfeit Ozempic (semaglutide) found in U.S. drug supply chain. U.S. Food and Drug Administration (content current as of 12/05/2025), 2025.