GLP-1 side effects: what semaglutide and tirzepatide share, and what helps

Nausea leads on both medicines, and diarrhoea comes second^1,2.

Percentage with each side effect, against placebo, in the US-label weight-loss trials of Wegovy (semaglutide 2.4 mg) and Zepbound (tirzepatide 5, 10 and 15 mg)^1,2. A range covers the three tirzepatide doses. In India, semaglutide 2.4 mg is sold as Wegovy and Poviztra, and tirzepatide as Mounjaro and Yurpeak^3,5,6,7.

Do not rank the two medicines from this table^1,2. The placebo groups show that the trials differed: nausea affected 16 % on placebo in the semaglutide trials but 8 % in the tirzepatide trials^1,2.

In the US-label trials, 6.8 % of people stopped semaglutide 2.4 mg for good because of side effects, against 3.2 % on placebo¹. On tirzepatide 5, 10 and 15 mg, 4.8 %, 6.3 % and 6.7 % stopped, against 3.4 % on placebo².

SURMOUNT-5, a separate head-to-head trial, enrolled adults with obesity and without type 2 diabetes, all in the United States, its results record shows^8,9. Each person took the highest dose they could tolerate: tirzepatide 10 or 15 mg, or semaglutide 1.7 or 2.4 mg⁸. Non-serious nausea affected 44 % on each medicine, and non-serious vomiting 15 % on tirzepatide against 21 % on semaglutide⁹. The maker of tirzepatide ran this open-label trial, in which doctors and patients knew the medicine given^10,11. The full tirzepatide and semaglutide comparison also covers weight loss, and the semaglutide side effects guide has semaglutide-only detail.

Both medicines slow how fast the stomach empties⁴. A Cleveland Clinic specialist in the US says side effects are often at their worst in the first three to four weeks, while emptying is slowest¹². Under the US label, semaglutide for weight loss starts at 0.25 mg a week and rises every 4 weeks to a usual long-term (maintenance) dose of 2.4 mg¹. Under its US label, tirzepatide starts at 2.5 mg for 4 weeks and rises in 2.5 mg steps². In India, the Yurpeak KwikPen comes in 2.5 to 15 mg strengths⁷.

The US tirzepatide label adds that nausea, diarrhoea and vomiting events decreased over time². If side effects bother you or do not go away, the NHS says to get advice and keep taking the medicine unless told to stop^13,14. The step-by-step semaglutide dose schedule shows each step.

The NHS, an expert consensus and US medical societies give advice that centres on meals:

• If nausea keeps coming back, drink between meals, 30 to 60 minutes before or after eating¹⁵.
• Choose smaller, more frequent meals, and avoid fatty food in the first days of treatment¹⁶.
• Keep away from hot, greasy or strong-smelling food, such as bhature or kachori, while the nausea lasts¹⁷.
• Do not lie down soon after eating, and skip a large drink with the meal¹⁷.

The NHS says it is best to avoid alcohol on either medicine, because it can make nausea and vomiting worse^13,14. If you keep vomiting and no fluid stays down, get medical help the same day¹⁸.

The table above gives the rates for burping, indigestion and bloating. Food stays in the stomach longer on these medicines, so a big meal can trigger nausea and heavy reflux^4,12. General NHS advice for heartburn: skip the foods and drinks that trigger it, leave 3 to 4 hours between your last meal and sleep, and avoid tight waistbands¹⁹. An Indian expert panel agreed that eating slowly and avoiding a large evening meal can improve tolerance²⁰. Ask your doctor before you treat acidity with a remedy from the chemist.

Both are on the NHS lists of common side effects for each medicine^13,14. Feeling full can cut how much people drink, which can make constipation more likely¹⁵. An expert consensus advises moving more and taking more water and fibre, and says a stool softener can be considered¹⁵. See a doctor if constipation is not improving, keeps returning, or comes with blood in the stool (NHS)²¹. For diarrhoea, a joint US advisory says that avoiding large or high-fat meals can help¹⁶.

Diarrhoea and vomiting drain fluid, and the US labels link that loss to kidney injury^1,2. To prevent dehydration, an Indian expert panel advises over 2 litres a day of water or sugar-free drinks²⁰. Anyone on a fluid limit set by a doctor should follow that limit instead.

Hair loss affected 3 % on semaglutide 2.4 mg against 1 % on placebo, and 4–5 % on tirzepatide 5 to 15 mg against 1 % (US labels)^1,2. Hair regrowth is covered in the semaglutide side effects guide. Tiredness is on the NHS list of common side effects for both medicines^13,14.

A hollower face, looser skin and deeper folds are increasingly reported during weight loss on GLP-1 medicines, says a 2026 review²². The review says the term "Ozempic face" can suggest an effect of the drug itself, but similar changes follow other large weight loss²². It says current evidence favours volume lost with the weight, on top of each person's own anatomy and ageing²². Whether faster weight loss makes this worse is still uncertain²².

A Government of India backgrounder puts pancreatitis, kidney injury and bowel obstruction at the severe end of GLP-1 side effects²³.

Emergency: dial 112, India's single emergency helpline number²⁴.

• Swelling of the throat or tongue, an itchy raised rash, or trouble breathing. These can signal anaphylaxis, a severe allergic reaction listed by the NHS for both medicines^13,14.

See a doctor straight away for:

• Severe stomach pain that will not settle, sometimes spreading to the back, with or without vomiting. It can mean an inflamed pancreas (pancreatitis). An NHS leaflet and the US Medication Guides for both medicines say to stop the medicine and contact a doctor straight away^1,2,4.
• Pain high in the stomach, fever, yellow skin or eyes, or pale, clay-like stools. The US Medication Guides for both medicines give these as signs of gallbladder problems^1,2.
• A gut that seems blocked, or severe constipation. Both US labels list ileus (a gut that stops moving) and intestinal obstruction in reports after approval^1,2.
• Sudden loss of sight, usually in one eye. The NHS lists this for semaglutide¹³.

Sweating, shaking, a pounding heartbeat, dizziness or confusion can mean low blood sugar^13,14. The US labels say the risk may be higher with insulin or sulfonylureas, diabetes tablets such as glimepiride^1,2,25. In people with diabetes, the NHS says to treat it quickly with something that raises blood sugar fast, such as fruit juice or a sugary fizzy drink²⁶. Then tell your doctor. If someone may have very low blood sugar and is not responding normally, or is unconscious, call 112^24,26. Give an unconscious person nothing to eat or drink²⁶.

Get medical help the same day for:

• Vomiting so often that no fluid stays down, or bloody diarrhoea¹⁸.
• New vision changes, if you have diabetic eye disease^1,2,13.

The US Wegovy and Zepbound labels also warn of severe digestive reactions, and advise against use in severe gastroparesis, a stomach that empties very slowly^1,2. Each US label carries a boxed warning: semaglutide caused thyroid C-cell tumours in rodents and tirzepatide in rats, and it is not known whether either does so in people^1,2. Under both US labels, people with MEN 2 (multiple endocrine neoplasia type 2) or a personal or family history of medullary thyroid cancer (MTC) must not use either medicine^1,2. Tell your doctor about a neck lump, difficulty swallowing, breathlessness, or a hoarse voice that lasts^1,2.

Patients can also report a suspected side effect to the Pharmacovigilance Programme of India (PvPI)²⁷. Use the "ADR PvPI" Android app, or call the helpline, 1800 180 3024, from 9:00 am to 5:30 pm on working days^27,28.

Tirzepatide (Mounjaro and Yurpeak in India) may make the contraceptive pill less effective, because it slows stomach emptying (US label)^2,3,7. The US label advises switching to a non-oral method, or adding a barrier method for 4 weeks after starting and after each dose increase². Ask your doctor which method suits you.

Check the active ingredient on the pack: semaglutide or tirzepatide. Lilly launched Mounjaro in India in March 2025, and Cipla launched Yurpeak, according to news reports^3,7. Reports in April 2026 said tirzepatide was still under patent in India and that no generic existed²⁹.

The table's semaglutide rates come from 2.4 mg, not from Ozempic's Indian diabetes strengths of 0.25, 0.5 and 1 mg^1,30. Semaglutide generics followed the March 2026 patent expiry, as reported, and the list of GLP-1 brands and generics in India names them^31,32. The rates here are for injections; tablets such as Rybelsus have their own guide³³.

PharmEasy, an Indian online pharmacy, lists Mounjaro as Schedule H, not sold over the counter³⁴. In April 2026, Reuters reported that Haryana's drug regulator had seized more than 260 suspected counterfeit Mounjaro pens; Reuters could not verify this official claim³⁵. The Government of India advises getting GLP-1 medicines only on prescription, through legitimate, regulated channels²³.

What are the main side effects of GLP-1 medicines? The US labels for Wegovy and Zepbound put nausea, diarrhoea, vomiting, constipation and stomach pain among the most common^1,2.

Which has fewer side effects, semaglutide or tirzepatide? The US label tables cannot answer this^1,2. In the head-to-head trial, run by the maker of tirzepatide, the most common side effects in both groups were digestive, and most were mild to moderate^8,10.

Can GLP-1 cause diarrhoea after eating? These medicines can cause diarrhoea, at the rates in the table; an NHS trust's leaflet advises smaller, less fatty meals^1,2,4.

What does GLP-1 do to your face? Weight loss can leave the face hollower, with looser skin; a 2026 review says similar changes follow other large weight loss²².

Who should avoid GLP-1 medicines? Under both US labels, people with MEN 2 or a personal or family history of MTC must not use either medicine^1,2. Other groups are in who should not take GLP-1 medicines.

Are there long-term side effects? The main trials ran 68 weeks (STEP 1, semaglutide) and 72 weeks (SURMOUNT-1, tirzepatide), so they say little about side effects over many years^36,37. Whether the rodent thyroid tumours apply to people is not known^1,2.

Talk to a Zelta specialist if you want to discuss side effects before or during treatment.