Managing GLP-1 Side Effects: Nausea, Constipation and Tiredness

Managing GLP-1 side effects mostly comes down to eating smaller, slower, lower-fat meals, drinking enough fluids and letting the dose rise gradually. The commonest problems (feeling sick, diarrhoea, constipation and vomiting) are usually worst when starting or increasing the dose, and ease over time for most people. Severe stomach pain that does not go away needs urgent medical help, not home remedies.

This guide covers Mounjaro (tirzepatide), Wegovy (semaglutide), the Wegovy pill and Foundayo (orforglipron), using UK patient leaflets, prescribing information and NHS advice as of September 2026. It is information only, not medical advice: all four are prescription-only, and a qualified prescriber decides whether one suits you. New to the class? Read what GLP-1 medications are.

Which GLP-1 side effects are most common?

For weight management, the leaflets for all four medicines class feeling sick, being sick, diarrhoea and constipation as very common (more than 1 in 10 people). Stomach pain, indigestion, bloating, reflux, tiredness, dizziness and hair loss are very common or common, depending on the medicine. The prescribing information (SmPC) gives the scale:

• Wegovy 2.4 mg (68 weeks): nausea 43.9% versus 16.1% on placebo, diarrhoea 29.7% (15.9%), vomiting 24.5% (6.3%) and constipation 24.2% (11.1%). Most were mild to moderate and short-lived, though constipation lasted longer; 4.3% stopped because of stomach side effects.
• Mounjaro (pooled SURMOUNT-1 and SURMOUNT-2 trials): nausea 24.6%, 29.0% and 28.0% on 5, 10 and 15 mg versus 8.5% on placebo. Stomach side effects were mostly mild (61.0%) or moderate (34.4%), and 1.9% to 4.3% stopped because of them, versus 0.5% on placebo.

These are separate trials, not a head-to-head; see our comparison page or GLP-1 medications compared.

Managing GLP-1 side effects: how do I ease nausea?

NHS advice on feeling sick, and an NHS hospital weight-management leaflet on tirzepatide, suggest:

• smaller, more frequent meals, eaten slowly, stopping when full
• bland, low-fat foods such as crackers or toast; avoid hot, fried, greasy or strong-smelling food
• sips of a cold drink rather than a large drink with meals
• ginger or peppermint tea, or ginger biscuits
• fresh air, and not lying down soon after eating

The NHS says it is best not to drink alcohol on tirzepatide or semaglutide, as it can make sickness worse. If nausea is not better within a few days or keeps coming back, speak to your prescriber, GP or pharmacist; a GP may prescribe anti-sickness medicine. Call NHS 111 if you keep being sick and cannot keep fluids down, or have been vomiting for more than 2 days.

What helps with constipation, diarrhoea and vomiting?

Constipation

The NHS suggests plenty of fluids, gradually adding fibre such as oats, wheat bran or linseed, fruit such as apples or apricots, a daily walk, and not delaying when you need to go. If that fails, a pharmacist can suggest a laxative.

Diarrhoea and vomiting

The main risk is dehydration, which the Mounjaro leaflet warns may reduce kidney function. Drink enough to keep your pee pale, and ask a pharmacist about oral rehydration solutions. Signs include thirst, dark yellow strong-smelling pee, peeing less often, dizziness and a dry mouth. Get an urgent GP appointment or help from NHS 111 if dizziness on standing does not go away, you are peeing less than normal, or your heart rate is fast.

Why do I feel tired or dizzy?

Tiredness is very common or common depending on the medicine, and dizziness is common; the Wegovy leaflets say dizziness happens mainly in the first three months. Both can signal dehydration, and the NHS hospital leaflet suggests eating little and often, with a balanced diet. Low blood pressure is common with Mounjaro (for weight management) and Foundayo. Do not drive or use machines while dizzy. With insulin or a sulfonylurea, dizziness, sweating or a fast heartbeat can mean low blood sugar.

What about indigestion, reflux and hair loss?

For heartburn, the NHS suggests smaller, more frequent meals, avoiding triggers such as coffee, alcohol, chocolate and fatty or spicy foods, and not eating within 3 or 4 hours of bed; a pharmacist can advise if it keeps happening. Hair loss is common: in weight-management trials it affected 4.9% on Mounjaro and 2.5% on Wegovy 2.4 mg, versus 1.0% on placebo, was mainly mild, and most people recovered while continuing treatment. The Wegovy leaflet says it may be more frequent at 7.2 mg.

Can a slower dose increase reduce side effects?

Yes, which is why each medicine starts low: Mounjaro stays at each dose for at least four weeks, Wegovy injections step up every four weeks over 16 weeks, the Wegovy pill steps up monthly, and Foundayo stays at each dose for at least 30 days. The Wegovy SmPC says a prescriber can consider delaying an increase, or dropping back a dose, if stomach symptoms are significant. Never change or stop your medicine without your prescriber. Schedules are on our Mounjaro, Wegovy, Wegovy pill and Foundayo pages.

Which GLP-1 side effects need urgent medical help?

What else should I know while taking a GLP-1 medicine?

• Operations: tell your healthcare team, including the anaesthetist, before a general anaesthetic or deep sedation; the MHRA says these medicines slow stomach emptying.
• Contraception: the Mounjaro leaflet says women with obesity or overweight on the pill should consider adding a barrier method, or switching to a non-oral method, for 4 weeks after starting and after each dose increase; the Foundayo leaflet says 30 days, for any woman on the pill. The MHRA says GLP-1 medicines must not be taken during pregnancy, while trying to get pregnant or while breastfeeding.
• Fake products: the MHRA warns against buying GLP-1 medicines from unregulated sellers such as beauty salons or social media, and has received reports of severe side effects from fakes.

How do I report a side effect?

Tell your prescriber or pharmacist about any side effect that bothers you or does not go away. You can also report suspected side effects, or a suspected fake medicine, to the MHRA Yellow Card scheme online or via its app. As of September 2026 all four medicines carry a black triangle for additional monitoring. More answers are on our FAQ page.

Frequently asked questions