By Dr Bianca Crook, South African general
practitioner
Medically reviewed: 1 September 2026
Most GLP-1 side effects are digestive and not emergencies, but severe or rapidly worsening symptoms should not be dismissed. Seek urgent medical help for severe persistent abdominal pain, repeated vomiting with inability to keep fluids down, signs of serious dehydration, breathing difficulty or swelling of the face or throat, collapse, severe low blood glucose, or sudden significant vision change.
Key points
- Severe symptoms need assessment even if they occur soon after an injection.
- Do not diagnose pancreatitis, gallbladder disease or bowel obstruction at home.
- Persistent vomiting can cause dehydration and kidney injury.
- Insulin or sulfonylureas can increase low-glucose risk when combined with some GLP-1 medicines.
- In an emergency, contact local emergency services; do not wait for an online reply.
Severe, persistent abdominal pain
Pancreatitis has been reported with GLP-1 medicines. A typical warning is severe, persistent upper abdominal pain, sometimes radiating to the back and sometimes accompanied by vomiting. The symptom is not specific enough to confirm pancreatitis, but it needs prompt medical assessment.
Gallbladder problems can also occur, particularly in the context of weight loss. Right-upper abdominal pain, fever, jaundice, pale stool or dark urine can signal gallbladder or bile-duct disease. These symptoms need clinical review and may need imaging or blood tests.
Do not keep taking extra pain medicine and assume the problem will pass. Contact urgent care or emergency services according to severity.
Repeated vomiting or dehydration
Nausea can be common, especially during escalation. Repeated vomiting, inability to retain fluids, very little urine, fainting, confusion, a racing heartbeat or marked weakness is different. Dehydration can contribute to acute kidney injury.
The risk may be greater in older adults, people with kidney disease, those using diuretics, and anyone with prolonged diarrhoea or vomiting. The next treatment step should be decided by a clinician after assessing the person, not by automatically repeating or skipping doses.
A swollen abdomen or inability to pass stool or gas
Constipation is common, but severe pain, progressive swelling, repeated vomiting, or inability to pass stool or gas can indicate a more serious gastrointestinal problem. Seek urgent assessment. Do not add more fibre or multiple laxatives when obstruction is a possibility.
For milder bowel symptoms, see Constipation on GLP-1 Treatment: What Is Common and When to Seek Help.
Serious allergic reaction
Breathing difficulty, swelling of the lips, tongue, face or throat, widespread hives, dizziness or collapse can signal anaphylaxis. Call emergency services immediately. Do not drive yourself if you are faint or having breathing difficulty.
Severe low blood glucose
GLP-1 medicines used alone do not usually cause the same hypoglycaemia risk as insulin, but the risk can rise when they are combined with insulin or sulfonylureas. Warning signs can include sweating, shaking, palpitations, intense hunger, confusion, unusual behaviour, drowsiness, seizure or loss of consciousness.
Patients using glucose-lowering combinations should have an individual hypoglycaemia plan. Severe confusion, seizure or unconsciousness is an emergency. A person who is not fully alert should not be given food or drink by mouth.
Sudden or significant visual symptoms
People with diabetes can have diabetic retinopathy, and rapid improvement in glucose has sometimes been associated with temporary worsening. Sudden loss of vision, a new curtain-like shadow, severe eye pain or abrupt major change in sight needs urgent eye assessment. Do not wait for the next routine appointment.
A neck lump or persistent swallowing symptoms
Some semaglutide and tirzepatide product labels contain a boxed warning about thyroid C-cell tumours observed in rodents. It is not known whether the medicines cause these tumours in humans. A neck lump, persistent hoarseness, trouble swallowing or breathing should be assessed. These symptoms are not usually an immediate emergency unless breathing is affected, but they should not be ignored.
Pregnancy, surgery and procedures
Contact the prescriber promptly if you become pregnant or plan pregnancy. Product-specific discontinuation advice applies, and weight loss is not pursued during pregnancy.
Tell the procedural and anaesthesia team that you use a GLP-1 medicine. Current multi-society guidance supports an individual risk assessment rather than one rule for everyone. Digestive symptoms, the escalation phase, dose and procedure type may affect the plan. Do not withhold or continue the medicine solely on the basis of an old social-media instruction.
What to take to urgent care
If possible, bring the medicine name, dose, last dose date, device or packaging, other medicines, allergies and a short timeline of symptoms. If the product came from a non-standard supplier, say so. That information can materially improve assessment.
Read What Should a Patient Know Before Starting a GLP-1 Medicine? before treatment and Why the GLP-1 Dose Is Not a Competition before escalation.
Before Your Next Injection explains common side effects and urgent red flags in the wider context of safe treatment.
Medical disclaimer: This list is not exhaustive and cannot diagnose an emergency. If symptoms are severe, rapidly worsening or feel dangerous, seek urgent medical care. Do not delay because a symptom might be a known medicine side effect.
Sources: FDA Wegovy prescribing information; FDA Zepbound prescribing information; EMA Wegovy product information; multi-society perioperative GLP-1 guidance; SAHPRA GLP-1/GIP product warning.