Semaglutide vs Tirzepatide: How They Differ, Side Effects and What to Ask

Semaglutide copies a gut hormone called glucagon-like peptide one, or GLP-1. It acts on receptors in the brain and gut that signal fullness, slows how quickly the stomach empties and helps the body release insulin when blood sugar rises.

Tirzepatide acts on the GLP-1 receptor and also on a second receptor for a hormone called GIP, short for glucose-dependent insulinotropic polypeptide. Because it works on two pathways it is sometimes called a dual agonist.

Both lower appetite and help with blood sugar control. Neither replaces changes to eating, activity and sleep, and both work only while they are being taken.

Semaglutide is sold as Wegovy for weight management and as Ozempic for type two diabetes, both as weekly injections. An oral form, Rybelsus, is used for diabetes.

Tirzepatide is sold as Zepbound for weight management in the United States and as Mounjaro, which in many countries is approved for both diabetes and weight management.

Approvals differ by country, so the country guides below link to each regulator.

Both are injected under the skin once a week, usually into the stomach, thigh or upper arm, using a pen or a vial and syringe. Prescribers start low and raise the dose in steps so the digestive system can adjust.

A missed dose, a change of brand or a switch between the two medicines should be discussed with the prescriber rather than worked out alone.

The side effects of both medicines are similar, and the most common are digestive: nausea, fullness, reflux, constipation or diarrhea, often worse after a dose increase. Eating smaller meals, slowing down and staying hydrated helps many people.

Less common but serious problems include pancreatitis, gallbladder problems and dehydration that affects the kidneys. Severe stomach pain, repeated vomiting or signs of an allergic reaction need urgent medical attention.

Rapid weight loss can also mean loss of muscle, so prescribers usually advise enough protein and some strength work.

In the United States both medicines carry a boxed warning for people with a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type two, and prescribers elsewhere ask about the same history. They are not used in pregnancy, and people planning a pregnancy are usually asked to stop in advance.

Anyone with a history of pancreatitis, severe digestive disease, diabetic eye disease or an eating disorder should raise it with the prescriber before starting.

The decision depends on your health conditions, other medicines, what is approved and available where you live, cost and how you tolerate side effects. It is a decision for you and a prescriber who knows your history.

If a clinic pushes one medicine without explaining why, or offers a switch without a review, ask for the reasoning.