Short answer: depression, anxiety and suicidal thoughts are not listed as side effects of Mounjaro (tirzepatide) or Wegovy (semaglutide) in their UK product information, as checked in October 2026. The MHRA, the UK medicines regulator, says the available data does not support a causal link between GLP-1 medicines, which in its guidance include Mounjaro, and depression or suicidal thoughts, and it keeps this under review. Your mood can still change during treatment for other reasons, such as eating much less, feeling tired or how you feel about your changing body, so tell your GP or pharmacist if a low mood lasts more than 2 weeks.
If you are having thoughts of suicide or harming yourself, get help now. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time. You can also call NHS 111 at any time, or text SHOUT to 85258 if you would rather not talk. You do not need to speak to us first.
This guide sets out what the UK product information says, what regulators and studies have found (as of October 2026), the other reasons mood can change during weight loss treatment, and what to do if yours does.
Can Mounjaro cause depression?
The evidence so far does not show that it does. Section 4.8 of the UK Summary of Product Characteristics (SmPC) for the Mounjaro KwikPen lists the side effects seen in clinical studies and reported since launch. Depression, low mood, anxiety and suicidal thoughts are not among them, and section 4.4, the warnings, says nothing about mood. The patient leaflet in the pack does not mention them either.
The leaflet does list some side effects that can affect how you feel from day to day, even though none of them is a mood problem:
| Side effect in the UK leaflet | How often |
|---|---|
| Feeling tired (fatigue) | Common in people treated for weight management, up to 1 in 10 |
| Feeling less hungry (decreased appetite) | Listed; reducing appetite and food cravings is how Mounjaro works, the leaflet says |
| Dizziness, and low blood pressure | Common in people treated for weight management, up to 1 in 10 |
| A fast pulse | Uncommon in people treated for weight management, up to 1 in 100 |
| A changed sense of taste | Uncommon, up to 1 in 100 |
| Low blood sugar, if you also take a sulphonylurea or insulin for diabetes | Very common with those medicines, more than 1 in 10. The signs include irritability, confusion, a fast heartbeat and sweating |
Several of these overlap with symptoms the NHS lists for depression and anxiety, such as feeling constantly tired, having no appetite, feeling dizzy and a noticeable or unusual heartbeat. That can make it hard to tell what is causing what, which is one more reason to talk to someone rather than guess. More on side effects is in our Mounjaro side effects guide.
What have regulators found about GLP-1 medicines and suicidal thoughts?
In 2023, reports of suicidal thoughts in people using GLP-1 medicines, including liraglutide and semaglutide (the medicine in Wegovy), led medicines regulators in Europe, the UK and the US to review them. Each concluded that the evidence does not show these medicines cause suicidal thoughts.
| Regulator | When | What it covered | What it found |
|---|---|---|---|
| European Medicines Agency (its safety committee, PRAC) | April 2024 | Dulaglutide, exenatide, liraglutide, lixisenatide and semaglutide. Tirzepatide was not included. | The available evidence does not support a causal link with suicidal thoughts or self-harm. No change to the product information. |
| MHRA (UK) | September 2024 | The same five medicines, and depression as well as suicidal thoughts | The available data does not support a causal link with suicide, suicidal thoughts, self-harm or depression. It keeps monitoring. |
| MHRA guidance for the public | Updated February 2026 | GLP-1 medicines, which it lists as including Mounjaro | The available data does not support a causal link with depression, suicidal thoughts or suicide. It will assess new data as it becomes available. |
| US Food and Drug Administration | January 2026 | 91 placebo-controlled trials with 107,910 people, and insurance records of more than 2.2 million people with type 2 diabetes | No increased risk of suicidal thoughts or behaviour, or of anxiety, depression, irritability or psychosis, in the trials, and no increased risk of self-harm in the records. It asked for the warning to be removed from the US labels of Saxenda, Wegovy and Zepbound, the US weight loss brand of tirzepatide. |
Why did US labels carry a warning? The FDA says the warning was in those labels from the day each medicine was approved, and was based on reports with a variety of older weight loss medicines, not on evidence about GLP-1 medicines. The UK product information for Mounjaro and Wegovy does not carry it.
What "no causal link" means. The evidence does not show that these medicines cause depression or suicidal thoughts. It is not a promise that nobody's mood will change while taking one, and the regulators say they keep watching new data. If you notice a change in yourself, take it seriously, whatever the cause.
What did the trials and large studies find?
Mounjaro (tirzepatide)
In the SURMOUNT-1, 2 and 3 weight loss trials, people answered standard questionnaires about depression (the PHQ-9) and suicidal thoughts (the C-SSRS) while taking tirzepatide or a placebo. A 2026 analysis of 4,056 of them, followed to week 72, found no sign of a higher risk of depression with tirzepatide than with placebo. Suicidal thoughts were reported by 0.6% of people in each group, most judged low risk. Suicidal behaviour that was not fatal was recorded in 0.1% of people on tirzepatide and in no one on placebo.
Two limits matter when you read those numbers:
- Who was studied. The analysis covered people with no known major mental illness. SURMOUNT-1, for example, did not include anyone with significant active or unstable major depression or another severe psychiatric condition in the previous 2 years, or anyone who had ever attempted suicide. The authors say further study in people with significant psychiatric illness may be warranted.
- How it was done. It was a post hoc analysis, looking back at trials that were designed to measure weight, and four of its seven authors work for Eli Lilly, which makes Mounjaro.
Wegovy (semaglutide)
A 2024 analysis of the STEP 1, 2, 3 and 5 trials of semaglutide 2.4mg, with 3,681 people in all, found no increased risk of depression symptoms or of suicidal thoughts and behaviour compared with placebo. No more than 1% of people reported suicidal thoughts or behaviour, with no difference between the groups. The same limits apply: these were people without a known major mental illness, and several of the authors work for Novo Nordisk, which makes Wegovy.
Health records
A US study of the health records of 240,618 people with overweight or obesity, published in 2024 and used in the European review, found no higher risk of suicidal thoughts in the 6 months after starting semaglutide than after starting other weight loss medicines. Studies of records like this can show links, but cannot prove cause on their own.
Put together, the evidence does not show that these medicines cause depression in people without a serious mental illness. There is much less evidence about people living with severe or recent depression, which is one reason our consultation asks about your mental health.
Can Mounjaro cause anxiety or mood swings?
Anxiety and mood swings are not listed side effects of Mounjaro in its UK leaflet either, and the FDA's review of 91 trials found no increased risk of anxiety or irritability with GLP-1 medicines. Some listed side effects can feel like anxiety, though. The NHS lists stomach problems, a noticeable or unusual heartbeat, feeling lightheaded or dizzy and getting tired easily among the symptoms of generalised anxiety disorder. Feeling sick, dizziness, a fast pulse and tiredness are all in Mounjaro's leaflet.
Mood swings can have other causes too. The NHS lists mood swings, low mood or depression among the symptoms of the perimenopause (our guide to Mounjaro and HRT covers this), and depression or anxiety among the main symptoms of PMOS, the condition that used to be called PCOS (see Mounjaro and PCOS). If you also take a sulphonylurea or insulin, the leaflet lists irritability and confusion among the signs of low blood sugar.
Why might your mood change during weight loss treatment?
Low mood during treatment is not always the medicine. The NHS says most people feel low sometimes, and lists pressure at work, relationship and money worries, illness and bereavement among the things that can bring it on. Some things that often change during weight loss treatment can affect how you feel too:
Eating much less. Mounjaro makes you feel less hungry, so you may eat much less than before. The NHS suggests regular meals to keep your energy levels stable, so try not to skip meals altogether. See what to eat on Mounjaro.
Tiredness. Tiredness is a common side effect, and feeling constantly tired is also on the NHS's list of depression symptoms. Our guide on whether Mounjaro makes you tired explains what helps.
Food and feelings. Mounjaro reduces hunger and food cravings, and a small number of people find food tastes different. If eating has been one of the ways you cope with stress or difficult feelings, that change can be unsettling, and it is worth talking about.
Body image. As your body changes, so can how you feel about it. Body image worries are common: in a 2019 Mental Health Foundation survey of 4,505 UK adults, 34% had felt anxious and 35% depressed because of concerns about their body image.
Alcohol. The NHS advises against using alcohol to lift a low mood, as it can contribute to poor mental health. Our guide to Mounjaro and alcohol covers drinking during treatment.
Hormones and life stage. The NHS lists mood changes among the symptoms of the perimenopause, and depression or anxiety among the main symptoms of PMOS (PCOS).
Weight and mood are linked both ways. A review of 15 long-term studies with 58,745 people, published in 2010, found that people with obesity had higher odds of developing depression later (an odds ratio of 1.55), and people with depression had higher odds of developing obesity (1.58). So many people start weight loss treatment already living with low mood, and a change during treatment is not always caused by the medicine. It still deserves attention.
Does low mood on Mounjaro go away?
It depends on the cause. The NHS says a low mood often gets better after a few days or weeks, and that a low mood lasting 2 weeks or more could be a sign of depression. It advises seeing a GP if:
- you have had a low mood for more than 2 weeks
- you are struggling to cope with a low mood
- the things you are trying yourself are not helping
The NHS also says you can refer yourself to an NHS talking therapies service for anxiety and depression without seeing a GP, if you are 18 or over (16 or over in some areas). If side effects are part of the picture, the Mounjaro leaflet says feeling sick and diarrhoea are most common when you first start and decrease over time in most people. Tell us if they do not.
What should you do if your mood changes on Mounjaro?
If you are at risk, get help now. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time. You can also call NHS 111 at any time.
Talk to someone you trust, and to your GP. The NHS suggests talking about your feelings with a friend, family member, health professional or counsellor. See your GP if a low mood lasts more than 2 weeks or you are struggling to cope.
Tell your pharmacist. If you are a Solira patient, message your pharmacist from your account, before your next dose if you can. Your pharmacist typically replies within 1 working day. We can look at your treatment with you, including staying at your current dose rather than going up, or stopping. Messages are not for emergencies.
Keep taking your other medicines. The NHS says never to stop an antidepressant suddenly or without talking to your doctor first. If you take lithium, tell us before you start: the NHS advises calling 111 if you have severe diarrhoea or vomiting, or are not eating and drinking much, because dehydration can affect your lithium level.
Report it. You, your pharmacist or your GP can report a suspected side effect to the MHRA through the Yellow Card scheme. Mounjaro is under additional monitoring (the black triangle), so reports help the MHRA spot new safety information quickly.
Can you take Mounjaro with depression, anxiety or antidepressants?
Having depression or anxiety does not on its own rule out Mounjaro. Neither is among the conditions the UK leaflet asks you to talk about before using it, and neither stops treatment with us by itself. Our consultation asks about your mental health as well as your physical health, so your pharmacist can take it into account:
- Depression or anxiety. Tell us. Your pharmacist reviews it with the rest of your answers.
- A serious mental illness, such as bipolar disorder or schizophrenia. Tell us. Your pharmacist reviews it before anything is supplied.
- An eating disorder diagnosed by a doctor, now or in the past (anorexia, bulimia or binge eating disorder). We cannot provide weight loss treatment online, and your GP is the right person to speak to.
- Every medicine you take, including antidepressants and lithium. Mounjaro slows how quickly your stomach empties, which can change how quickly tablets are absorbed, most of all when you start. The consultation asks about lithium by name.
Keep taking any medicine prescribed for your mental health. Because the large trials did not include people with significant or unstable depression in the previous 2 years, it is worth talking to your GP or mental health team as well as us if that applies to you. Will we tell your GP? We only tell your GP if you agree. In your consultation we ask, as a question of its own, whether you'd like us to tell your GP about your treatment, and we only do so with your consent.
Thinking about treatment? Our consultation asks about your mental health as well as your physical health, and a GPhC-registered pharmacist reviews your answers before anything is supplied.
Check your eligibilityCan Wegovy cause depression?
The evidence for Wegovy (semaglutide) points the same way. Depression and suicidal thoughts are not listed side effects in the UK product information for the Wegovy pens (revised September 2026) or Wegovy tablets (June 2026). Semaglutide was one of the five medicines in the 2024 European and UK reviews, and the STEP trial analysis above was of semaglutide. Foundayo (orforglipron), first licensed in the UK on 10 August 2026, does not list them either; it was licensed after those reviews. Our guide to whether Wegovy is safe covers its other risks, and Wegovy side effects covers the common ones, such as tiredness and dizziness.
See also is Mounjaro safe?, what happens when you stop taking Mounjaro and the weight loss service.