Lyng Pharmacy
Medicines A–Z · GIP/GLP-1 receptor agonist

Tirzepatide (Mounjaro)

A dual GIP and GLP-1 medicine · Written by the Lyng Pharmacy team, based on NHS and BNF guidance · Updated August 2026
Also sold asMounjaro
Type of medicineGIP/GLP-1 receptor agonist
Available asWeekly injection pen
How you get itPrescription only

Tirzepatide acts on two gut hormone receptors rather than one, which is what distinguishes it from semaglutide. It is licensed for type 2 diabetes and, separately, for weight management, and it is taken as a once-weekly injection.

What it is used for

Type 2 diabetes, and weight management in adults meeting specific BMI and health criteria alongside a reduced-calorie diet and increased physical activity.

As with all these medicines, it works with dietary change rather than replacing it, and weight is commonly regained after stopping unless those changes are sustained.

How to take it

Injected under the skin of the stomach, thigh or upper arm once a week, on the same day each week, with or without food. Rotate the site each time.

The dose is increased in steps over months, which substantially reduces gut side effects.

If you miss a dose, take it within four days and then resume your usual day. If more than four days have passed, skip it and take the next as scheduled. Never share a pen.

Store pens in the fridge before use, and follow the leaflet on storage after first use.

Side effects

Nausea, vomiting, diarrhoea, constipation, indigestion, reduced appetite and tiredness are common, worst after dose increases. Smaller meals, eating slowly and avoiding fatty food help considerably.

Seek urgent medical help for severe persistent stomach pain that may spread to the back, with or without vomiting — a possible sign of pancreatitis. Also for severe upper right abdominal pain with jaundice or fever, which can indicate gallbladder problems.

Report persistent vomiting with dehydration, and any vision changes if you have diabetes.

Hypos are unlikely with tirzepatide alone but possible alongside a sulfonylurea or insulin.

Cautions

Tirzepatide may reduce the effectiveness of oral contraceptives around the time of starting and dose increases — additional contraception is advised for four weeks after starting and after each dose increase. Ask us if this applies to you.

Tell any anaesthetist or endoscopist that you take it, as it slows stomach emptying.

Only obtain it from a registered pharmacy with a genuine prescription. Falsified weight loss pens sold online have caused serious harm in the UK.

Always read the label. This page is general information, not advice for your situation. Doses, warnings and interactions differ between products and between people. Check the leaflet inside your medicine, and ask our pharmacist if anything is unclear — that conversation is free and takes two minutes.

Questions about Tirzepatide (Mounjaro)?

1 Lyng Lane, West Bromwich B70 7RW · Mon–Fri 8:30am–6pm, Sat 9am–1pm · 0121 500 5756

Ask our pharmacist →

Frequently asked questions

How is tirzepatide different from semaglutide?
Tirzepatide acts on two gut hormone receptors (GIP and GLP-1) rather than one. Both are weekly injections used in type 2 diabetes and, separately, weight management.
Does tirzepatide affect the contraceptive pill?
It can reduce the effectiveness of oral contraception around starting and dose increases. Additional contraception is advised for four weeks after starting and after each increase.
What if I miss a dose of tirzepatide?
Take it within four days and resume your usual day. If more than four days have passed, skip it and take the next as scheduled.
Should I tell my anaesthetist I take tirzepatide?
Yes. GLP-1 medicines slow stomach emptying, which matters before surgery or any procedure involving sedation.

Related pages

Semaglutide for weight management →Semaglutide for type 2 diabetes →Metformin →All medicines A–Z →

More from Lyng Pharmacy

Order a repeat prescription →Pharmacy First — NHS treatment without a GP →Free medicine review →Contact us & opening hours →
0121 500 5756