Semaglutide vs Tirzepatide: Uses, Side Effects & FAQs

Semaglutide and tirzepatide are once-weekly injections for type 2 diabetes and for weight loss in adults with obesity. Use either one only on a doctor's prescription and under a doctor's care. Semaglutide copies one natural gut hormone, while tirzepatide copies two, which is the main difference between them. Both lower blood sugar, reduce appetite and help you feel full sooner, and tirzepatide led to more weight loss when the two were compared directly.

Both are injectable medicines that work like hormones your gut releases after a meal. Semaglutide is sold as Ozempic (for diabetes), Wegovy (for weight) and Rybelsus (a daily tablet for diabetes). Tirzepatide is sold as Mounjaro, and as Zepbound for weight loss in some countries.

Check the exact strength printed on your pen or vial, because each strength is a different pack and Indian packs may differ from other countries. Semaglutide tablets (Rybelsus) are taken daily and are used differently from the injections. In India, CDSCO's expert committee recommended tirzepatide in a prefilled pen in April 2023, and a locally made semaglutide injection for type 2 diabetes in September 2025.

Think of them as copies of the "I have eaten" signal your gut sends to your brain and pancreas:

1. Release insulin: Both tell the pancreas to release insulin when blood sugar is high, and to make less of the hormone that raises sugar.
2. Slow the stomach: Both slow down how quickly food leaves your stomach, so sugar enters the blood more gently and you stay full longer.
3. Quiet hunger: Both act on the brain's appetite centres, so you feel hungry less often and eat smaller portions.
4. Add a second signal: Tirzepatide also switches on the receptors for GIP, a second gut hormone that boosts insulin release.

The overall result is steadier blood sugar and lower calorie intake, which leads to weight loss over months.

Doctors usually prescribe semaglutide or tirzepatide for:

• Type 2 diabetes, where the body cannot use insulin properly and blood sugar stays high
• Obesity, generally a BMI of 30 or more
• Overweight with a weight-related illness, such as high blood pressure, high cholesterol or sleep apnoea, generally a BMI of 27 or more
• Lowering heart attack and stroke risk in some adults with diabetes or heart disease (approved for some brands)
• Kidney protection in adults with type 2 diabetes and chronic kidney disease (approved for Ozempic)
• Obstructive sleep apnoea, where breathing stops and starts during sleep, in adults with obesity (approved for Zepbound)

Approved uses differ by brand and by country, and Indian labelling may differ. Indian guidelines define obesity at a lower BMI (25 or more) for Asian Indians, so your doctor will decide which limits apply to you. Neither medicine is approved for type 1 diabetes, and neither replaces a healthy diet and regular activity.

The weight figures come from a head-to-head study in adults with obesity but without diabetes, using the highest dose each person could tolerate. The blood sugar figures are from adults with type 2 diabetes already taking metformin.

1. Inject once a week on the same day, at any time, with or without food.
2. Inject under the skin of your tummy or thigh; use the upper arm only if someone else injects for you.
3. Change the exact spot each week, and use a different spot from any insulin injection.
4. Use a new needle every time, and never share your pen, even with a new needle.
5. If you need to change your injection day, keep at least 2 days between doses for semaglutide and 3 days for tirzepatide.
6. Read the instructions inside your pack, because pens and vials are prepared differently.

Your doctor decides your dose based on why you are taking it, your blood sugar, your weight and how well you tolerate it.

• Ozempic: Usually starts at 0.25 mg once a week for 4 weeks, then 0.5 mg. It may go up to 1 mg and then 2 mg, with at least 4 weeks at each step.
• Wegovy: Usually starts at 0.25 mg once a week and rises every 4 weeks. The usual maintenance dose is 2.4 mg once a week (up to 7.2 mg in some countries).
• Mounjaro: Usually starts at 2.5 mg once a week. It rises by 2.5 mg at a time, at least 4 weeks apart, to a maximum of 15 mg once a week.

Never increase the dose on your own. A faster climb does not bring faster results, but it does raise the risk of severe vomiting and dehydration. Do not use the two medicines together, and switch from one to the other only on your doctor's advice.

In some countries, Wegovy is approved for children 12 and older and Mounjaro for children 10 and older, only under a specialist. Never use an adult's pen for a child.

If you inject too much, contact your doctor or go to the nearest hospital emergency department straight away. In an emergency, call 112 or 108 for an ambulance, and carry the pen or vial with you.

For semaglutide injections, take the missed dose if it is 5 days or less since it was due; otherwise skip it. For tirzepatide, the window is 4 days. Then carry on with your usual day, and never take two doses to make up.

If you miss two or more doses in a row, speak to your doctor before restarting. You may need to restart at a lower dose to avoid strong nausea.

The full effect takes several months, because the dose is raised step by step, at least 4 weeks apart. See your doctor if your sugar readings do not improve, or if side effects stop you from eating and drinking normally.

Keep unused pens and vials in the fridge at 2°C to 8°C, in their box, away from light, and never freeze them. Rules for room-temperature storage (up to 30°C) differ by brand, from 21 days to 56 days, so follow the leaflet in your pack and keep the medicine out of children's reach.

Most side effects are stomach-related. They are usually mild to moderate and are most common in the first weeks and after each dose increase.

Common and mild:

• Nausea and vomiting
• Diarrhoea or constipation
• Stomach pain, bloating or indigestion
• Less appetite
• Tiredness
• Redness or itching where you inject
• Hair thinning

Rare but serious (stop the medicine and see a doctor right away):

• Severe stomach pain that spreads to your back and does not go away, with or without vomiting (possible inflamed pancreas)
• Pain in the upper right tummy, fever or yellow eyes (possible gallbladder problems)
• Swelling of the face, lips or throat, or trouble breathing (allergic reaction)
• A lump or swelling in the neck, hoarse voice or trouble swallowing
• Sudden changes in vision, or very little urine after heavy vomiting or diarrhoea

The stomach side effects come from the slowed stomach emptying, which both medicines cause.

• Personal or family history of medullary thyroid cancer
• Multiple endocrine neoplasia type 2 (MEN 2), an inherited gland-tumour condition
• Serious allergy to the medicine or any ingredient

Both medicines carry the US FDA's strongest (boxed) warning on their 2026 labels, because they caused thyroid tumours in rats and mice. It is not known whether this happens in people.

Tell your doctor before taking semaglutide or tirzepatide if you have:

• Past pancreatitis (inflamed pancreas) or gallstones
• Diabetic eye disease (retinopathy can worsen when sugar drops fast)
• Severe stomach-emptying problems (gastroparesis)
• Kidney disease (vomiting and diarrhoea can cause dehydration)
• A fast resting heartbeat (these medicines can raise heart rate slightly)
• A planned surgery, endoscopy or sedation (food may stay in the stomach)
• Pregnancy, breastfeeding or plans to get pregnant (stop semaglutide at least 2 months before trying, and tirzepatide at least 4 weeks before)

Always tell your doctor about every medicine, supplement or home remedy you are using. It is best to avoid alcohol, because it can make nausea and vomiting worse.

See a doctor quickly if you have:

• Vomiting or diarrhoea that stops you keeping fluids down
• Severe stomach or back pain that does not settle
• Shakiness, sweating, confusion or a racing heart (possible low sugar)
• Blurred vision or sudden vision loss in one eye
• A neck lump, hoarse voice or difficulty swallowing
• A positive pregnancy test while on the medicine

Semaglutide and tirzepatide both help control type 2 diabetes and support long-term weight loss when your doctor prescribes them. The right choice depends on your health, other medicines and tolerance. Inject once a week, raise the dose only as your doctor advises, and never combine the two. Nausea and other stomach upsets are common early on and usually settle with time.

This article is for general information only and is not a substitute for advice from a qualified doctor or pharmacist. Always consult a healthcare professional before starting, stopping or changing any medicine.