Mounjaro

Mounjaro is a once-weekly injection containing tirzepatide. Tirzepatide is a dual GIP and GLP-1 receptor agonist, meaning it acts on two gut-hormone pathways rather than one.

Mounjaro is used, alongside diet and exercise, to improve blood sugar control in adults with type 2 diabetes. It is also used for weight management in eligible adults, supporting appetite control and weight reduction.

Mounjaro provides strong blood sugar (HbA1c) lowering and can lead to substantial weight reduction, reflecting its dual action on the GIP and GLP-1 pathways.

Tirzepatide activates both the GIP and GLP-1 receptors. It boosts insulin release and lowers glucagon in a glucose-dependent way, increases the body's sensitivity to insulin, slows stomach emptying and reduces appetite and food intake.

Mounjaro is injected under the skin (subcutaneously) into the abdomen, thigh or upper arm once a week, with or without food, rotating the injection site. Treatment starts at 2.5 mg weekly for 4 weeks (a starting dose, not yet for full effect), then increases to 5 mg, with further 2.5 mg steps at least 4 weeks apart if needed, up to a maximum of 15 mg weekly.

The most common side effects are nausea, diarrhoea, decreased appetite, vomiting and constipation, mostly mild to moderate and most likely during dose increases. Indigestion, burping, wind and reflux can also occur.

Like other GLP-1 medicines, this medicine carries a boxed warning about the risk of thyroid C-cell tumours (including medullary thyroid carcinoma, MTC). These tumours were seen in rodent studies; the relevance to humans is not established. Do not use Mounjaro if you or a family member have had medullary thyroid cancer or MEN 2, or if you have had a serious allergic reaction to tirzepatide. It is not for type 1 diabetes and has not been studied in people with a history of pancreatitis. Seek urgent advice for severe, persistent tummy pain (possible pancreatitis).

Use with caution if you have a history of pancreatitis or significant digestive problems. If you also use insulin or a sulfonylurea, your risk of low blood sugar is higher and those doses may need lowering. Mounjaro may reduce how well some other medicines are absorbed, and may make oral contraceptives less reliable for a time after starting or increasing the dose - ask your prescriber about back-up contraception. Discuss pregnancy or breastfeeding with your prescriber.

Store in a refrigerator at 2-8°C; do not freeze. If needed, a pen or vial can be kept unrefrigerated below 30°C for up to 21 days. Keep in the original carton to protect from light.

If you miss a dose, take it as soon as possible within 4 days (96 hours) of the missed dose. If more than 4 days have passed, skip it and take your next dose on the usual day. Always leave at least 3 days between two doses.