How safe is GLP-1 treatment, and who should not take it?

The most common side effects are digestive^3,5. In the trial that compared tirzepatide with semaglutide head to head, most were mild to moderate and came mostly while the dose was being raised⁵.

In the weight-loss trials behind the US labels, nausea affected 44 % of people on semaglutide 2.4 mg against 16 % on placebo³. With tirzepatide the figure was 25–29 %, against 8 %⁴. Our semaglutide side effects guide has the full table, and GLP-1 side effects, medicine by medicine adds tirzepatide.

The US Wegovy label also lists serious risks, among them:

• Pancreatitis, an inflamed pancreas³.
• Acute gallbladder disease, which includes gallstones³.
• Acute kidney injury, sudden damage to the kidneys³.
• Severe digestive reactions³.
• Pulmonary aspiration: stomach contents can enter the lungs under general anaesthesia or deep sedation³.
• Complications of diabetic retinopathy, an eye disease, in people with type 2 diabetes³.

The US label for tirzepatide (Zepbound) warns about the same six risks⁴. These rates and warnings come from US labels and from trials run in many countries. India's Press Information Bureau (PIB) gives a similar range in a 2026 backgrounder, from common nausea and vomiting to severe pancreatitis, kidney injury and bowel obstruction⁶.

Press reports date the Indian launches of Mounjaro (tirzepatide) to 20 March 2025 and of Wegovy (semaglutide 2.4 mg) to 24 June 2025^7,8. Generic semaglutide brands followed in March 2026⁹.

The US labels rule out people with a personal or family history of MTC, people with MEN 2, and people with a past serious allergy to the medicine^3,4. The NHS (UK) says neither medicine is used in pregnancy or while breastfeeding^1,2.

Who must not use each medicine, and when it is not used. Sources: the US labels for Wegovy and Zepbound, and the NHS (UK) guides^1,2,3,4.

The NHS adds that either medicine may not be suitable after an allergic reaction to another GLP-1 medicine^1,2.

The thyroid rows trace back to animal studies. Semaglutide caused tumours of the thyroid's C cells in rodents, and tirzepatide did so in rats^3,4. Whether either medicine does this in people is unknown^3,4. MTC is a cancer of those same C cells¹⁰.

These limits come from the US labels and the NHS, so in India the doctor checks them against the leaflet of the brand prescribed. PharmEasy, an Indian online pharmacy, lists Wegovy and Mounjaro as Schedule H medicines that are not sold over the counter^11,12. Raise any row that fits you with the doctor.

The US labels name two conditions in the thyroid warning: MTC and MEN 2^3,4. Other thyroid problems are not on that list.

MTC develops in the C cells of the thyroid, which make the hormone calcitonin¹⁰. An inherited change in a gene called RET can cause it, so family history matters¹³. If a relative had thyroid cancer and nobody knows the type, tell the doctor. MEN 2 is a genetic condition, and the US National Cancer Institute lists it among the risk factors for thyroid cancer¹³.

Both US labels ask doctors to tell patients the signs of a thyroid tumour: a neck lump, trouble swallowing, shortness of breath, or lasting hoarseness^3,4. Report any of them to the doctor.

An underactive thyroid is a different condition, but the doctor needs to hear about it as well. The NHS lists levothyroxine, a medicine for an underactive thyroid, among the medicines that may not mix well with semaglutide¹. Tell the doctor about any thyroid condition or thyroid medicine before treatment starts.

The conditions below are not on the US labels' must-not list, but each one needs the doctor's attention first. Tell the doctor before your first dose.

Conditions that need extra checks. Sources: the US labels for Wegovy and Zepbound, and the NHS (UK) guides^1,2.

The two pregnancy rules for tirzepatide come from different bodies, so ask the doctor which one to follow; our page on semaglutide and pregnancy has more. In India, the PIB says GLP-1 medicines must be taken under medical supervision⁶.

A PTI launch report said Mounjaro's Indian weight-management indication covers adults with a body mass index (BMI) of 30 or more, or 27 or more with a weight-related condition¹⁵. Separately, Mounjaro was launched in India for type 2 diabetes¹⁵.

For semaglutide, a stock-exchange filing by Zydus gives the same two cut-offs for its injection's weight-management use¹⁶. One report of the Wegovy launch gave no BMI figures⁸.

India's own definition of obesity starts lower. A government backgrounder defines obesity as a BMI of 25 or more, and overweight as 23.00 to 24.99⁶. An Indian consensus statement says the limits of normal BMI are narrower and lower in Asian Indians than in white Caucasians¹⁷.

In June 2026, the expert committee of CDSCO, India's drug regulator, noted that obesity and overweight are defined differently for US and Asian populations¹⁸. The committee kept the BMI cut-offs in tirzepatide's Indian indication¹⁸. One set of numbers defines obesity, and the other sets who the medicine is indicated for.

A BMI figure alone does not decide treatment. The government advises the public to consult a qualified medical specialist before use, and our page on who is a good candidate for GLP-1 treatment describes that assessment⁶.

In India, the PIB advises the public to get GLP-1 medicines only on prescription, through legitimate and regulated channels⁶. By 24 March 2026, regulators had inspected 49 businesses over GLP-1 sales, among them online pharmacy warehouses and slimming clinics¹⁹.

The sources differ on who may prescribe. A health-ministry release of 24 March 2026 on the sale of weight-loss drugs says approval came with a prescription condition¹⁹. The named prescribers are endocrinologists and internal medicine specialists, and cardiologists for some indications¹⁹. In 2023, CDSCO's expert committee recommended a similar condition for tirzepatide²⁰. A news summary from March 2026 reported a government warning that generic semaglutide must be sold only on a registered medical practitioner's prescription²¹. The sources do not settle the question.

Counterfeit pens are a second risk. In April 2026, Haryana's drug regulator was reported to have seized more than 260 suspected counterfeit Mounjaro pens, an official claim that Reuters could not verify²². The NHS (UK) warns that some websites sell fake weight-loss medicines². If a doctor prescribes a GLP-1 medicine for you, use a registered pharmacy.

Semaglutide now reaches patients in India under many brand names, and each contains semaglutide^9,23. Most of the generic approvals in the CDSCO minutes read for our research are for type 2 diabetes²⁴. The semaglutide cautions on this page come from the US Wegovy label and the NHS, so the doctor checks the leaflet of the brand prescribed. Our guide to GLP-1 brands and generics in India lists them; for products sold online under a GLP-1 name, see GLP-1 supplements and patches.

Much of the lost weight returned in a trial that tested stopping. In the STEP 1 extension, people who stopped semaglutide 2.4 mg and its lifestyle programme had regained two-thirds of the weight they had lost a year later²⁵. That is a group figure, not a forecast for one person.

The NHS (UK) advises talking to a doctor before choosing to stop semaglutide or tirzepatide, and not stopping suddenly^1,2. For people with type 2 diabetes, stopping semaglutide could affect blood sugar¹. If milder side effects bother you, the NHS advice is to speak to a doctor and keep taking the medicine unless told to stop^1,2. More is in what happens when semaglutide stops.

Call 112, India's single emergency number, if you see either of these²⁶:

• A serious allergic reaction (anaphylaxis): a swollen throat or tongue, a raised itchy rash, or difficulty breathing, listed by the NHS for both medicines^1,2.
• Someone who may have very low blood sugar and is not responding normally, or is unconscious²⁷. If they are unconscious, the NHS says to give them no food or drink²⁷.

Get medical help straight away for:

• Severe stomach pain that does not go away, with or without nausea or vomiting. Both US Medication Guides say to stop the medicine and call the doctor right away^3,4. The NHS says pancreatitis can cause severe stomach or back pain that does not go away¹.
• Upper stomach pain, yellow skin or eyes, fever or clay-coloured stools. The US Medication Guides for both medicines list these as possible signs of gallbladder problems^3,4. The tirzepatide guide says to tell the doctor right away⁴.
• Sudden loss of vision, usually in one eye, which the NHS lists for semaglutide¹.
• A gut that seems blocked, or severe constipation. India's government lists bowel obstruction among the severe complications of GLP-1 medicines⁶. The US labels for both medicines list reports collected after approval, including intestinal obstruction and severe constipation^3,4.

Low blood sugar: treat it at once, then tell the doctor. The NHS lists its signs as sweating, shaking, a pounding heart and dizziness, and with tirzepatide also headache, weakness and confusion^1,2. The NHS says it needs quick treatment, which people can usually give themselves²⁷. If you have diabetes, the NHS suggests something that raises blood sugar fast, such as a small glass of fruit juice or a sugary fizzy drink²⁷. Under the US labels, the risk may be higher with insulin or a sulfonylurea^3,4.

The same day: general NHS advice is to get medical help for vomiting that stops you keeping fluids down, or for bloody diarrhoea²⁸. Both US labels link kidney injury to fluid loss^3,4. If you have diabetic eye disease, contact the doctor the same day about changes in vision¹.

You or the doctor can also report any suspected side effect to the Pharmacovigilance Programme of India (PvPI)²⁹. Its helpline is 1800 180 3024 on working days, and its 'ADR PvPI' Android app takes reports^29,30.

Is GLP-1 worth the risk? It depends on the person. A doctor weighs the expected benefit against the risks on this page. Which GLP-1 is best for weight loss sets out what the trials show.

Who should not take GLP-1? Under the US labels, people with MEN 2, a past serious allergy to the medicine, or a personal or family history of MTC must not use semaglutide or tirzepatide^3,4. The NHS (UK) adds that neither is used in pregnancy or while breastfeeding^1,2.

Will I regain weight after stopping GLP-1? In the STEP 1 extension, people had regained two-thirds of the weight they had lost a year after stopping semaglutide 2.4 mg and its lifestyle programme²⁵. Talk to the doctor before you stop^1,2.

What should I avoid when taking semaglutide? The NHS says it is best not to drink alcohol, because it can make nausea and vomiting worse; see alcohol and semaglutide¹. Tell the doctor if you take insulin, a sulfonylurea, warfarin or levothyroxine^1,3. Before a general anaesthetic or sedation, tell the surgeon, anaesthetist or dentist that you use semaglutide¹.

Is Ozempic available in India? Yes. Novo Nordisk launched Ozempic in India on 12 December 2025, a news report said³¹. It is sold in 0.25 mg, 0.5 mg and 1 mg strengths for type 2 diabetes, and Novo Nordisk sells its 2.4 mg weight-loss dose as Wegovy³².

What qualifies you for semaglutide? A doctor decides, after an assessment. The BMI section above gives the cut-offs reported in India and how they differ from India's definition of obesity.

Should I be worried about taking semaglutide? The most common side effects on the US label are digestive: nausea, diarrhoea, vomiting, constipation and stomach pain³. The NHS says most serious side effects are rare¹, and the warning signs above are the ones to know.

Talk to a Zelta specialist to go through your own health history before any prescription.