Semaglutide side effects: what to expect, and when to call your doctor

Nausea is the most common side effect, at 44 % against 16 % on placebo¹. Each figure only means something next to the placebo figure, because people on a dummy injection also report nausea and headaches.

Side effects in the weight-loss trials of semaglutide 2.4 mg once a week, against placebo¹. Source: the US prescribing label for Wegovy.

The NHS lists most of the same effects as common, hair loss among them, and adds skin reactions where the injection goes in⁶. In India, this weight-loss dose is sold as Wegovy, launched on 24 June 2025, and as Poviztra^7,8. These rates come from the trials behind the US label, not from a study in India.

Semaglutide slows how fast the stomach empties after a meal, so you can feel full sooner and for longer than before². An obesity specialist at the Cleveland Clinic in the US says side effects are often worst in the first three to four weeks, when stomach emptying is slowest⁹.

For this reason the US label starts the weight-loss injection low and steps the dose up slowly, to lower the risk of digestive side effects¹. It starts at 0.25 mg once a week for 4 weeks¹. The dose then rises to 0.5 mg, 1 mg and 1.7 mg, each for 4 weeks, and the usual long-term (maintenance) dose is 2.4 mg once a week¹. In India, Wegovy comes in a pre-filled pen in five dose strengths⁷.

Digestive side effects are more likely at the start and soon after each increase, and they usually settle once the maintenance dose is reached^3,10. If one step is too hard to cope with, the US label lets the doctor delay the next step by 4 weeks¹. Each step and its timing are set out in our semaglutide dose schedule.

Advice from expert groups and the NHS lines up closely, and most of it is about how much, and how fast, you eat:

• Eat smaller portions, eat only when you are hungry, and stop when you feel full³.
• Eat slowly. The brain can take up to 30 minutes after a meal to register a full stomach⁹.
• Avoid fried, fatty and greasy food^2,11. Pakoras, samosas, puris and rich gravies all count.
• Do not lie down soon after eating^3,11.
• Do not have a large drink with a meal¹¹. If nausea keeps coming back, drink 30 to 60 minutes before or after meals instead³, and sip water through the day⁹.
• Have breakfast, then small meals every 3 to 4 hours with enough fluids; ginger or peppermint tea may also help¹².

If these changes do not help, tell your doctor soon rather than waiting it out³. If you keep vomiting and cannot keep fluids down, get medical help that day⁵.

Constipation lasts longer than the other digestive side effects. In an analysis that combined the main weight-loss trials, half of the people with constipation had it for 47 days or longer³.

Constipation. The medicine makes people feel full, so many drink less water, and that can make constipation more likely³. The usual advice is more water, more fibre and more movement through the day, and a doctor may suggest a stool softener³. Go easy on extra fibre when your stomach already feels bloated or tight after a dose, because it may be too much for the gut at that point⁹. See a doctor if constipation does not improve, keeps coming back, comes with regular bloating, or you see blood¹³.

Diarrhoea and dehydration. Avoiding large or fatty meals can help with diarrhoea¹². According to the US label, most kidney problems reported with semaglutide happened in people who had become dehydrated after nausea, vomiting or diarrhoea¹. The UK medicines regulator advises plenty of fluids, such as water, throughout treatment, and warns that severe dehydration can damage the kidneys badly enough to need hospital care¹⁰.

An Indian expert panel advises more than 2 litres a day of water or drinks without sugar¹⁴. If your doctor has told you to limit fluids, follow that advice instead. A simple check from the NHS is to drink enough that your urine stays pale¹⁵.

Burping affected 7 % of people on semaglutide 2.4 mg against under 1 % on placebo¹. Indigestion affected 9 % against 3 %¹. Food stays in the stomach longer on this medicine, so a large meal can bring on nausea and a lot of acid reflux^2,9.

For reflux, general NHS advice is to avoid the foods and drinks that set it off¹⁶. Finish eating 3 to 4 hours before bed, and skip clothes that are tight around the waist¹⁶. An Indian expert panel says eating slowly and avoiding large evening meals can improve tolerance and reduce nausea¹⁴. Alcohol can make nausea and reflux worse; the NHS advises avoiding it^6,12. Ask your doctor before you add any medicine for acidity.

Both tiredness and headache were more common than on placebo, as the table shows¹. Hair loss is less frequent, at 3 % against 1 %¹, although the NHS still lists it among the common side effects⁶. A 2026 systematic review found rapid weight loss to be a possible contributor, through a type of shedding called telogen effluvium¹⁷. The American Academy of Dermatology, a US body, lists a loss of 20 pounds (about 9 kg) or more among the common triggers of this shedding¹⁸. Once the trigger has passed and the body has adjusted, the shedding stops, and hair usually regains its fullness within six to nine months¹⁸. If the trigger does not go away, the shedding can continue for a long time¹⁸.

Some signs need prompt care. India's government lists severe pancreatitis, kidney injury and bowel obstruction among the complications of GLP-1 medicines¹⁹.

Call 112, India's emergency number, at once for:²⁰

• A serious allergic reaction: a swollen throat or tongue, a raised itchy rash, or difficulty breathing⁶.
• Very low blood sugar in someone who is not responding normally, or is unconscious²¹. Do not give an unconscious person food or drink²¹.

Get medical help straight away for:

• Severe stomach pain that does not go away and may spread to the back, with or without vomiting. This can be a sign of an inflamed pancreas (pancreatitis). The US Medication Guide says to stop the medicine and call the doctor right away¹.
• Sudden loss of vision, usually in one eye⁶.
• Pain in the upper stomach, yellow skin or eyes, fever, or pale (clay-coloured) stools. These can be signs of gallbladder problems, including gallstones¹.
• Severe constipation, or a gut that seems blocked. Reports collected after approval include ileus (the gut stops moving), intestinal obstruction and severe constipation¹.

Contact your doctor the same day for:

• Vomiting that stops you keeping fluids down, which risks dehydration and kidney harm, or bloody diarrhoea^1,5.
• Changes in your vision, if you have diabetic eye disease⁶.

Low blood sugar can cause sweating, shaking, a pounding heart or dizziness, and the US label says the risk may be higher with insulin or a sulfonylurea^1,6. For a person with diabetes, the NHS says it needs quick treatment, such as a small glass of fruit juice²¹. Then tell your doctor.

The US label also carries a boxed warning on thyroid tumours. Semaglutide caused thyroid C-cell tumours in rodents, and whether it does so in people is not known¹. Medullary thyroid cancer starts in these C cells²². People with a personal or family history of it, or with MEN 2 (multiple endocrine neoplasia type 2), must not use semaglutide¹. The US label asks doctors to tell patients the signs to report: a lump in the neck, trouble swallowing, shortness of breath, or hoarseness that does not go away¹.

Before an operation or a dental procedure with a general anaesthetic or a sedative, tell the doctor or dentist that you use semaglutide⁶. For milder side effects that bother you or do not go away, speak to your doctor, and keep taking the medicine unless you are told to stop⁶. You can also report a suspected side effect yourself to India's Pharmacovigilance Programme (PvPI), whose helpline is 1800 180 3024 on working days^23,24.

Semaglutide is sold in India under several brand names, for diabetes and for weight loss. Rybelsus tablets are sold for type 2 diabetes in 3, 7 and 14 mg strengths²⁵, and the GLP-1 tablets guide covers them. Novo Nordisk launched the Ozempic injection here on 12 December 2025²⁶. According to Novo Nordisk India in December 2025, Ozempic comes in 0.25 mg, 0.5 mg and 1 mg strengths for type 2 diabetes, and the 2.4 mg weight-loss dose is kept for Wegovy²⁷.

The patent on semaglutide expired in India on 20 March 2026²⁸. Generic brands followed that month, including Noveltreat (Sun Pharma), Obeda (Dr Reddy's) and Sundae (Eris)²⁹. CDSCO is India's drug regulator. Most of the generic approvals that we read in its minutes are for type 2 diabetes, and some brands are reported for weight management too³⁰. Our guide to GLP-1 medicines in India lists more brands.

Most of the same side effects can occur with any brand, because the active ingredient is the same. The rates in the table were measured at the 2.4 mg weight-loss dose, and they may be different at the lower doses used for diabetes^1,27. Before you start any brand, check these three points:

1. A prescription. India's government advises getting GLP-1 medicines only on prescription, through regulated channels¹⁹. Pharmacy listings show Ozempic and Wegovy as prescription-only (Schedule H) medicines^31,32. In March 2026, the government was reported to have warned that generic semaglutide must be sold only with a registered doctor's prescription³³. For weight-loss drugs, a health-ministry release names specialists³⁴.
2. A registered pharmacy. In April 2026, Haryana's drug regulator was reported to have seized more than 260 suspected counterfeit Mounjaro pens³⁵. Mounjaro (tirzepatide) is a different medicine. The NHS warns that some websites sell fake weight-loss medicines, and advises a registered pharmacy³⁶.
3. Storage in the heat. Pens differ between brands, so follow the leaflet in your own pack. According to PharmEasy, an Indian online pharmacy, Wegovy pens stay in a fridge at 2–8 °C before first use and are never frozen³⁷. It also says never to use a pen that has been frozen, left in a hot car or in direct sun³⁷. For comparison only, the US label allows the Wegovy FlexTouch pen 56 days at 15–30 °C, or in the fridge, after first use¹.

Is Ozempic the same as semaglutide? Yes. Ozempic is a brand of semaglutide, sold in India in 0.25 mg, 0.5 mg and 1 mg strengths for type 2 diabetes^26,27. It can cause the same kinds of side effect, but the rates on this page come from the 2.4 mg weight-loss dose¹.

What happens if I stop semaglutide? Talk to your doctor first, and do not stop suddenly⁶. For people with type 2 diabetes, stopping could also affect blood sugar⁶. In the STEP 1 trial extension, people stopped both semaglutide 2.4 mg and the lifestyle programme³⁸. A year later, they had regained, on average, two-thirds of the weight they had lost³⁸.

Is semaglutide right for me? That depends on your health and on the other medicines you take. Some people must not use it at all, as our page on who should not take GLP-1 medicines sets out. Readers comparing it with tirzepatide can see GLP-1 side effects, medicine by medicine. Talk to a Zelta specialist about your own options.