Are GLP-1 Injections Safe? A UK Guide (October 2026)

01 · The core answer

So, are GLP-1 shots safe for you?

For most adults who meet the licensed criteria, yes, with sensible monitoring. Mounjaro is a once-weekly prescription injection licensed in the UK for weight management and type 2 diabetes.¹ It is used alongside a reduced-calorie diet and increased physical activity, and it is supplied only after a consultation reviewed by a GPhC-registered prescriber.

The decision most readers face is whether the medicine suits their own history.

For wider context, see our guides on whether GLP-1 is safe and UK risks and side effects.

02 · Suitability

Who should not take GLP-1 injections?

You should not take Mounjaro if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while trying to conceive. Mounjaro must not be used during pregnancy, and it should be stopped at least one month before trying to conceive. If you become pregnant during treatment, stop the medicine and tell your prescriber promptly. Your prescriber will take extra care, or may recommend against treatment, if you have a history of pancreatitis, severe gut or digestive disease, diabetic retinopathy, or gallbladder problems. Always share your full medical history and medicine list during consultation.¹

Related guides: How safe are glp 1 drugs and Are glp 1 agonists safe.

Related guide: Safe glp 1 alternative.

03 · Common side effects

Common side effects and what is normal

Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.¹³ Experiences differ widely: some people notice appetite change in week one, others feel little until a higher dose, and both are normal.

Everyone starts on 2.5mg once a week. That starting dose is about letting your body adjust, not about weight loss itself. After at least 4 weeks the dose increases to 5mg, then can step up by 2.5mg at a minimum of 4-week intervals, up to a maximum of 15mg weekly.¹ Higher is not automatically better, and your prescriber guides the pace.

04 · Serious risks

Serious risks: when to seek help

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing.¹

If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion). Your prescriber may need to adjust those medicines.¹

05 · Thyroid, kidneys, mood

Thyroid, kidneys, liver and mood

In rodent studies tirzepatide caused thyroid C-cell tumours; it is not known whether this applies to humans, and no increase has been shown in human trials. Tell your prescriber if you or a close relative have had medullary thyroid cancer or the inherited condition MEN 2. Routine thyroid monitoring is not required for most people.¹

Mounjaro is not known to damage kidneys or liver directly. The practical risk is indirect: severe vomiting or diarrhoea can cause dehydration, which can strain the kidneys, so keep fluids up and contact your clinical team if you cannot keep fluids down.¹

On mood, the EMA's safety committee reviewed the evidence and concluded in 2024 that it does not support a causal link between GLP-1 medicines and suicidal thoughts, and the MHRA keeps this under continuous review. Even so, tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment.¹⁷

If you have thoughts of harming yourself or ending your life, get help straight away. Call 999 or go to A&E if you are in immediate danger. In England you can call NHS 111 and choose the mental health option, any time. You can also call Samaritans free on 116 123, day or night. Tell your prescriber about any change in your mood while taking Mounjaro.

06 · Injecting safely

How to inject safely and avoid mistakes

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food. Licensed sites are the stomach area (at least 5cm from the belly button), the front of the thigh, or the back of the upper arm if someone else gives the injection. Rotate the site with each dose.¹³

If you miss a dose, take it within 4 days (96 hours) of the scheduled time; after that, skip it and never take two doses within 3 days of each other.¹

07 · Counterfeit risk

Unregulated sellers: the avoidable risk

The most avoidable danger is buying from sellers offering to supply without a consultation or prescription. Genuine supply matters: we dispense Mounjaro through official LillyDirect supply, and our pharmacy is GPhC-registered (9012878). The MHRA publishes counterfeit medicine alerts and runs the Yellow Card scheme, where you can report any side effect.⁷