Semaglutide Safety in 2026: Updated Scientific Review

Updated 15 July 2026. Semaglutide is a GLP-1 receptor agonist used under approved indications for type 2 diabetes and chronic weight management. Its clinical benefits are well established, but rapidly expanding use makes an up-to-date understanding of known and emerging risks essential. This review summarises regulatory conclusions and safety information available through July 2026.

This article is intended for healthcare and pharmaceutical professionals. It does not replace the approved product information, clinical guidance or individual medical advice.

Common adverse reactions

The most frequent adverse reactions are gastrointestinal: nausea, vomiting, diarrhoea, constipation and abdominal pain. They are often more pronounced during dose escalation and may decrease over time. Gradual titration in accordance with the approved product information can improve tolerability.

• Dehydration and renal impairment: prolonged vomiting or diarrhoea may cause fluid loss and requires timely clinical assessment.
• Gallbladder disease: weight loss and GLP-1 receptor agonist treatment are associated with gallstones and cholecystitis.
• Hypoglycaemia: risk is primarily increased when semaglutide is combined with insulin or a sulfonylurea.

Uncommon but serious risks

Acute pancreatitis

Product information continues to warn about acute pancreatitis. Persistent severe abdominal pain, particularly when radiating to the back or accompanied by vomiting, requires urgent assessment. Routine pancreatic-enzyme testing in asymptomatic patients should not be presented as a universal measure; monitoring depends on the product information, clinical circumstances and medical judgement.

Thyroid C-cell tumour warning

Thyroid C-cell tumours occurred in rodent studies, while relevance to humans remains uncertain. Contraindications and warnings in the applicable approved product information must be followed. Routine serum calcitonin testing or thyroid ultrasound has uncertain value as a universal early-detection strategy.

Diabetic retinopathy

Rapid improvement in glucose control can temporarily worsen diabetic retinopathy in patients with pre-existing disease. These patients require monitoring in line with clinical guidance.

New safety update: NAION and sudden vision changes

In June 2025, the EMA Pharmacovigilance Risk Assessment Committee concluded that non-arteritic anterior ischaemic optic neuropathy (NAION) is a very rare adverse effect of semaglutide medicines, potentially affecting up to 1 in 10,000 users. WHO also issued a safety alert and recommended that NAION be reflected in risk-management planning.

Patients who experience sudden loss of vision or rapidly worsening eyesight should seek medical attention without delay. If NAION is confirmed, further semaglutide treatment should be managed in accordance with current product information and regulatory recommendations.

Suicidal thoughts: current regulatory conclusion

After reviewing clinical trials and post-marketing data, FDA announced in January 2026 that it had not identified an increased risk of suicidal ideation or behaviour with GLP-1 receptor agonists. FDA requested removal of the related warning from US labelling for certain medicines. New or significant mental-health symptoms should still receive appropriate clinical assessment regardless of treatment.

Compounded and unapproved semaglutide

A separate group of risks involves unapproved or compounded products rather than authorised medicines. FDA has received reports of dosing errors, including cases requiring hospitalisation. Contributing factors included variable concentrations, multidose vials, confusion between milligrams, millilitres and “units”, and inappropriate syringe sizes.

• Compounded products do not undergo the same pre-market assessment of quality, safety and effectiveness as approved medicines.
• Semaglutide sodium and semaglutide acetate are salt forms different from the active ingredient in FDA-approved products; the regulator does not have sufficient information to establish equivalence.
• FDA warned in 2025 about counterfeit Ozempic found in the US supply chain. Medicines should be obtained only through legitimate, verifiable channels.

Practical risk-minimisation measures

1. Use semaglutide only for approved indications and according to current product information.
2. Follow the recommended titration schedule and do not change the dose without clinical guidance.
3. Consider pancreatitis history, gallbladder disease, diabetic retinopathy, concomitant therapy and contraindications before treatment.
4. Counsel patients about symptoms requiring urgent assessment: persistent severe abdominal pain, severe dehydration, serious hypersensitivity and sudden vision deterioration.
5. When insulin or a sulfonylurea is used, assess hypoglycaemia risk and whether dose adjustment is needed.
6. Avoid unapproved, counterfeit or improperly labelled products.
7. Report suspected adverse reactions to the national pharmacovigilance system and the marketing authorisation holder.

Why this matters for pharmacovigilance

Semaglutide illustrates why a medicine’s safety profile must be reassessed throughout its lifecycle. Marketing authorisation holders need timely literature and regulatory monitoring, signal assessment, risk-management plan updates, product-information maintenance and clear communication with healthcare professionals and patients.

PharmExpert supports literature and regulatory monitoring, adverse-event case management, signal management, aggregate reports and risk-management plans across CIS and EAEU markets.

Conclusion

The benefit–risk balance of approved semaglutide medicines remains positive when they are used as authorised with appropriate precautions. Major developments since the original review include recognition of NAION as a very rare adverse reaction, clarification that a suicidality signal was not confirmed, and stronger warnings about unapproved, compounded and counterfeit products.

Current authoritative sources

1. WHO: semaglutide medicines and the risk of NAION, 27 June 2025.
2. EMA PRAC: NAION as a very rare adverse effect, 6 June 2025.
3. FDA: conclusion on suicidal ideation and behaviour, 13 January 2026.
4. FDA: concerns with unapproved GLP-1 drugs, current information.
5. FDA: dosing errors with compounded injectable semaglutide.