Are There Any Long Term Effects of Mounjaro? (October 2026)

01 · The core answer

What are the long term effects of Mounjaro?

The long-term effects of Mounjaro fall into three groups: the benefits that continue while you take it, the side effects that are known and manageable, and the questions science cannot yet answer.

On the benefit side, trial participants lost meaningful weight and, on average, improved their waist size, blood pressure, cholesterol and blood-sugar measures. On the risk side, serious pancreas and gallbladder problems are uncommon, thyroid tumours have been seen only in rodent studies, and regulators have reviewed whether there is a link with mood. On the unknown side, very long follow-up in the general population is still limited.

02 · Your decision

Is this relevant to you, and what should you do next?

This matters most if you are weighing up whether to start, or whether to stay on treatment beyond the first few months. The sensible next step is a conversation with a prescriber who has your full medical history.

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. It is used alongside a reduced-calorie diet and increased physical activity. Individual results vary.¹

If you decide to go ahead, a free online consultation is reviewed by a GPhC-registered prescriber.

Related guides: Cheapest Mounjaro Long-Term Use UK and Are there any long term side effects of mounjaro and Can mounjaro cause long term effects and Do we know long term effects of glp 1 and Does mounjaro have long term side effects.

03 · What trials show

What the trials actually show over time

In the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.²

These are trial averages. Individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.² Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight.²

It is worth being clear about what this does and does not tell you. A trial of this length shows results over that period while people kept taking the medicine. It cannot tell you what happens to your body across many years.

Another point on trial results: they describe groups, not individuals. Someone might do far better or far worse than the average, and the average itself depends on the dose people were able to reach and tolerate. Your prescriber is the right person to talk through what a realistic expectation looks like for you.

04 · How it works

How Mounjaro works, and why that matters long term

Tirzepatide is the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1. Together these help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.¹

In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet. This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic).¹ Ozempic is semaglutide licensed for type 2 diabetes. It is not a UK weight-loss medicine.

05 · Gut and pancreas

Stomach, pancreas and gallbladder over time

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, as this could be pancreatitis. Also seek immediate medical help for pain in the upper right abdomen, fever or yellowing of skin or eyes, which could signal gallbladder problems, or for signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing.¹³

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. That is why sharing your full medical history at consultation matters.¹

06 · Thyroid, kidneys, liver

Thyroid, kidneys and liver

The thyroid question is the one most people have heard about. 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.¹

As a precaution, tell your prescriber if you or a close relative have had medullary thyroid cancer or the inherited condition MEN 2. They will weigh this in your assessment. Routine thyroid monitoring is not required for most people.¹

On kidneys and liver, Mounjaro is not known to damage either directly, and no dose adjustment is needed for mild to moderate kidney or liver impairment. People with severe impairment need individual prescriber assessment.¹

The practical risk is indirect. Severe vomiting or diarrhoea can cause dehydration, which can strain the kidneys. Keep fluids up, and get medical help straight away if you cannot keep fluids down. This applies at any point in treatment, including after months of feeling fine, for example during a stomach bug or after a dose increase.¹

07 · Mood and mind

Mood and mental health

Regulators have looked specifically at whether GLP-1 medicines are linked to low mood or suicidal thoughts. The EMA's safety committee reviewed the evidence and concluded that it does not support a causal link, and the MHRA keeps this under continuous review.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.

That said, any big change in weight, appetite and routine can affect how you feel. Tell your prescriber about any history of depression, and seek help promptly if your mood drops or you have distressing thoughts during treatment.¹⁷

08 · Wider health effects

Beyond the scales: the wider health picture

Not every long-term effect is a risk. In trials, weight loss on tirzepatide came with average improvements in waist size, blood pressure, cholesterol and blood-sugar measures, and most participants with prediabetes returned to normal blood-sugar levels.²

These are trial-average secondary outcomes, not promises. But they are why prescribers talk about weight management as health management rather than appearance.

A fair way to weigh the long-term question is therefore to compare two things: the known and monitored risks of treatment, and the known risks of the condition it treats. Your prescriber can help you do that for your own circumstances.

09 · Stopping and aftercare

Stopping treatment and staying monitored

Tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. There is no way to speed this up, and nothing needs doing while it clears.¹

Talk to your prescriber before you stop, so you have a plan for diet, activity and follow-up.

While you are on treatment, ongoing monitoring is how long-term effects get caught early. Our prescribing team provides monthly reviews, dose-titration and follow-up assessments, plus side-effect support. Repeat orders re-check suitability, and there is no auto-shipping, so you stay in control. If you notice anything new, tell your prescriber and report it through the Yellow Card scheme.¹⁹

10 · Who should avoid it

Who should not take Mounjaro

Mounjaro is not suitable for everyone. You should not take it if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while trying to conceive.¹ Mounjaro should be stopped at least one month before trying to conceive, and if you become pregnant during treatment, stop the medicine and tell your prescriber promptly.

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. Always share your full medical history and medicine list at consultation.¹³

Mounjaro is available on the NHS, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition.⁴