Can Mounjaro Cause Mental Health Issues? (October 2026)

01 · The core answer

Can Mounjaro cause mental health issues?

Regulators have looked at this and the EMA's safety committee concluded in 2024 that the evidence does not support a causal link between GLP-1 medicines and low mood or suicidal thoughts.¹⁷

Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly, licensed in the UK for weight management in adults and for type 2 diabetes.¹ It works by activating the GIP and GLP-1 gut-hormone receptors, which helps regulate appetite and slows how quickly the stomach empties.¹

For a wider look at the topic, our guides on whether Mounjaro affects mental health and Mounjaro mental health side effects go into further detail.

02 · Your next step

What should you do if you feel different on Mounjaro?

Speak to your prescriber or GP about any new or worsening emotional symptom, however mild it seems. Do not stop or change your dose on your own without talking it through first.

It helps to note when the feeling started, how it relates to injection day or a dose increase, and what else has changed: sleep, appetite, stress, other medicines, alcohol. That timeline lets a clinician work out whether the medicine, the lifestyle change or something unrelated is the most likely driver.

If you are having thoughts of harming yourself, get medical help straight away. Call 999 or go to A&E if you are in immediate danger, and tell them you take Mounjaro. Tell someone you trust as well; you should not manage this alone.

03 · Indirect routes to low mood

Why you might feel low even if the medicine isn't the direct cause

Several things change at once when you start Mounjaro, and any of them can colour how you feel. Separating them is the first step to finding the right response.

Appetite shifts are the most obvious. Tirzepatide helps regulate appetite and slows stomach emptying, so most people feel fuller sooner and less hungry between meals.¹ Treatment is meant to work alongside a reduced-calorie diet, not an extreme one.²

If you take insulin or a sulfonylurea, low blood sugar is a particular consideration. Their doses may need adjusting when you start Mounjaro; that is not the same as saying they must never be combined. Raise it before you begin.

None of this means the medicine is blameless. It means a mood change deserves a proper look rather than a single assumption, and a clinician is best placed to do that with you.

04 · Mood and personality

Does Mounjaro change your mood or personality?

What people describe as feeling different is worth taking seriously, whatever the cause.

Tirzepatide activates GIP and GLP-1 receptors and, together, these help regulate appetite, slow stomach emptying and improve the body's response to insulin.¹

If you feel emotionally flat, unusually irritable, more anxious or just not yourself, tell your prescriber. If a symptom is new and you suspect the medicine, you can also report it through the Yellow Card scheme.¹⁹ Reports help the regulator monitor safety, but a report is not evidence that the medicine caused the problem.

Our broader pages on Mounjaro and mental health and weight loss drugs and mental health cover the surrounding questions.

05 · Before you start

Who should take extra care, and what to tell your prescriber

If you have a history of depression, anxiety, an eating disorder or self-harm, say so during your consultation. If you have thoughts of harming yourself or ending your life, get medical help straight away.

Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber.¹ The consultation is where your history, your current medicines and your goals are considered together.

Useful things to share include:

• any current or past mental health diagnosis, and any treatment for it
• other medicines you take, including antidepressants, insulin or sulfonylureas
• any history of disordered eating, or a difficult relationship with food
• whether you could become pregnant, and how you prevent it

Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed.⁷ The SmPC advises switching to a non-oral method, or adding a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.¹ It is a good example of why a full conversation matters: some of the most useful advice is about things people do not think to mention.

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. 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. 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.

06 · Stopping and monitoring

What about stopping, and how should you monitor yourself?

If you stop Mounjaro, tirzepatide takes roughly four to five weeks to clear the system, and there is no way to speed this up.¹

Please do not stop suddenly just because of a passing wobble, and equally do not push on through something that is distressing you. The right path is a conversation with your prescriber, who can review your dose and your circumstances, and who will tell you whether pausing, adjusting or continuing makes sense.

A simple monitoring habit can help:

• Note your mood, sleep and appetite briefly each week, ideally on the same day.
• Share patterns, not just single bad days, at your monthly review.
• Ask someone close to you whether they have noticed any change.

If you suspect a side effect, you can also report it through the Yellow Card scheme.¹⁹

07 · Other things to avoid

What should you avoid, and which medicines need care?

Oral contraceptives may be absorbed less well, and insulin or sulfonylureas may need dose adjustments because of the risk of low blood sugar.⁷ If you take medicines for your mental health, tell your prescriber, and do not change them yourself. Your GP or the prescriber who started them should be part of any decision.

Mounjaro works alongside a reduced-calorie diet and increased physical activity, not instead of them.² Eating regularly, sleeping well and staying active are sensible foundations for both physical and emotional wellbeing, whatever treatment you use.

08 · Serious side effects

Serious side effects: when to get help straight away

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. 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

09 · NHS and private routes

NHS and private care: where to take a mental health concern

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, and the NHS primary-care rollout began in June 2025 with the highest-need groups first.⁴ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment.

Whichever route you take, your GP remains the right first contact for mental health concerns. If you buy privately, you are still entitled to ask your GP for support with your mood, and we encourage you to keep them informed.

Out of hours, or in a crisis, use NHS 111 or emergency services instead.

Our guide on what mental health medications cause weight loss looks at the connection from the other direction, and does Mounjaro cause fertility issues covers another common safety question.