GLP-1 side effects: when to seek help

Symptoms needing urgent action

Call 999 for signs of a severe allergic reaction, such as sudden swelling of the tongue or throat, difficulty breathing, collapse or inability to wake someone normally. Use a prescribed adrenaline auto-injector if available and follow its instructions. [2]

Seek urgent medical help for severe abdominal pain that persists, especially if it spreads to the back, with or without vomiting. The MHRA strengthened pancreatitis warnings in January 2026, including rare severe and fatal cases. If pancreatitis is suspected, treatment should be stopped pending medical assessment; confirmed pancreatitis means it should not be restarted. [3]

Seek urgent assessment for sudden loss of vision or rapidly worsening sight while taking semaglutide. The MHRA identifies NAION, an optic-nerve condition, as a very rare risk. Do not wait for an ordinary eye-test appointment. [4]

When urgent advice is needed and your prescriber is unavailable, contact your local urgent-care service, such as NHS 111 where available. Use 999 for an emergency. Take the medicine name, strength and timing of the last dose with you.

Common does not mean unimportant

Common effects include nausea, vomiting, diarrhoea and constipation. A symptom list cannot diagnose a new problem. [1]

For a non-urgent review, describe the symptom rather than only saying you feel “rough”. Note when it began, whether it follows a dose change, how often it occurs, and whether it stops you eating, drinking, sleeping or working. Tell the clinician about other medicines and recent illness too.

Do not increase a dose just because a calendar says the next step is due when significant symptoms are unresolved. Contact the prescribing service for a decision. The Wegovy label, for example, allows a clinician to delay escalation or reduce to the previous dose when gastrointestinal symptoms are significant. [5]

Vomiting, diarrhoea and dehydration

Signs of dehydration include dark urine, urinating less, thirst and dizziness. If nausea makes drinking difficult, the NHS advises starting with small sips and building up. A pharmacist can advise on oral rehydration solutions when fluid and salts have been lost. [6]

Seek prompt medical advice if you cannot keep fluids down, are passing very little urine or remain dizzy on standing. Confusion, unusual sleepiness or signs of shock need emergency help. Someone already given a fluid restriction needs individual advice rather than a generic daily fluid target. [6]

A useful record includes the last time you passed urine, what you have managed to drink and how often you have vomited. Do not let record-keeping delay help if you are becoming seriously unwell.

Low blood glucose and other diabetes medicines

The risk of hypoglycaemia needs particular attention when treatment is combined with insulin or a sulfonylurea. The prescriber may need to adjust those medicines. Ask for a glucose-monitoring and hypo-treatment plan instead of changing doses yourself. [7][8]

Shaking, sweating, palpitations and confusion can be symptoms of a hypo. Follow the plan provided by your diabetes team. Never give food or drink to someone who cannot swallow safely; unconsciousness or abnormal responsiveness requires emergency action. [9]

Tell the clinician if episodes recur or if you no longer recognise the warning signs. Include whether you were driving, exercising or eating less than usual when discussing what happened.

Pregnancy, procedures and pre-existing conditions

Discuss pregnancy plans before treatment. Semaglutide should be stopped at least two months before a planned pregnancy and tirzepatide at least one month before. Tirzepatide users taking oral contraception need additional barrier protection for four weeks after starting and each increase, or a suitable non-oral method. [10]

Tell the anaesthetic team before general anaesthesia or deep sedation. These medicines can delay stomach emptying and affect aspiration risk even after fasting. Follow the team's individual instructions; do not independently stop or continue on the basis of a generic online interval. [11]

Tell the prescriber about previous pancreatitis, severe digestive problems, kidney problems and eye disease. Ask what those conditions mean for the particular product being considered, rather than treating every medicine in the group as identical.

Foundayo's UK leaflet gives a three-week interval before planned pregnancy and contraception precautions for 30 days after starting or increasing treatment. [12] Read the full product-specific advice with your prescriber; do not copy another medicine's interval.

Reporting a suspected side effect

The MHRA Yellow Card scheme accepts suspected side-effect reports; certainty that the medicine caused the problem is not required. Reporting supports safety monitoring and does not replace medical care. [13]

Keep the product name, batch number if available, strength, treatment dates and symptom timeline. Include other medicines and the action taken. You can ask a pharmacist or clinician to help with a report, particularly if you are unsure which product details are needed.

At follow-up, agree who will contact you and what should trigger an earlier call. Ask for the plan in writing if several medicines are being changed at once.

Questions and answers