Mounjaro low mood and anhedonia: feeling flat on treatment

In short

The Mounjaro SmPC lists no psychiatric side effects, including depression or suicidal thoughts
EMA PRAC (April 2024) and MHRA (September 2024) found the evidence does not support a causal link between GLP-1 medicines and suicidal thoughts
Pooled SURMOUNT data (4,056 people): suicidal ideation in 0.6% on tirzepatide and 0.6% on placebo
The trials largely excluded people with major depression in the past 2 years or a past suicide attempt
Urgent help: NHS 111, choosing the mental health option, Samaritans free on 116 123 at any time, 999 if life is at risk

Some people feel flat, low or less interested in things they used to enjoy while on Mounjaro. Low mood and depression are not listed as side effects in the UK prescribing information. The European Medicines Agency and the MHRA reviewed GLP-1 medicines in 2024 and found the evidence does not support a causal link with suicidal thoughts or self-harm. Feeling low still matters, whatever the cause. Speak to your GP, and if you feel unsafe call NHS 111 and choose the mental health option, Samaritans on 116 123, or 999.

What the regulators found

The EMA review

In July 2023 the European Medicines Agency's safety committee, PRAC, started a review after case reports of suicidal thoughts in people using liraglutide and semaglutide. The committee looked at clinical trials, post-marketing data and published studies. In April 2024 PRAC concluded the available evidence does not support a causal association between GLP-1 receptor agonists and suicidal and self-injurious thoughts and actions. It decided no change to the product information was needed.

The MHRA review

The MHRA published its own conclusion in September 2024. It found the available data does not support a causal association between GLP-1 receptor agonists and suicide, suicidal thoughts, self-injury or depression. The MHRA made no changes to product information and will keep monitoring the risk of severe psychiatric reactions.

Where tirzepatide fits

Both reviews named five medicines: dulaglutide, exenatide, liraglutide, lixisenatide and semaglutide. Tirzepatide was not one of them. The MHRA's current public guidance on GLP-1 medicines, which covers Mounjaro, says the available data does not support a causal association with depression and the MHRA will keep monitoring.

The Mounjaro Summary of Product Characteristics (SmPC) lists no psychiatric side effects at all.

What the tirzepatide trials showed

A pooled analysis of SURMOUNT-1, SURMOUNT-2 and SURMOUNT-3, published in the journal Obesity in 2026, looked at mood questionnaires from 4,056 adults over 72 weeks.

Measure	Tirzepatide	Placebo
Depression score moved to a worse category	18.2%	24.3%
Depression score moved to a better category	52.4%	41.8%
Any suicidal thoughts reported	0.6%	0.6%
Suicidal behaviour	2 people	None

Psychiatric side effects overall did not differ between the groups.

The trials have a limit worth knowing. They largely excluded people who had major depression in the previous 2 years, a history of bipolar disorder or schizophrenia, or a past suicide attempt. If any of these apply to you, the trial results tell you less, and your prescriber should check your mood more closely.

Feeling flat: what people describe

Anhedonia means losing interest or pleasure in things you used to enjoy. It is not listed as a side effect of Mounjaro, but people describe it:

Food no longer feels enjoyable, even favourite meals
Less excitement about social plans built around eating or drinking
A general sense of "flatness" rather than sadness
Less motivation for hobbies or exercise

Food as a reward

Mounjaro reduces appetite through the brain's appetite signals. Many people describe the end of constant thoughts about food (see food noise). For someone who used food to relax, celebrate or cope with stress, losing this reward leaves a gap. The feeling can be real even if the medicine does not act on mood directly.

If food was your main way of coping, the emotional eating guide has ideas for building other ways to unwind.

Other causes worth checking

Several common problems on Mounjaro cause low mood or flatness on their own:

Eating too little. A low intake drains energy and mood. See the eating too little page.
Tiredness. Fatigue is a very common side effect, and constant tiredness feels like low mood. The fatigue page covers what to check.
Low iron, vitamin B12, vitamin D or an underactive thyroid, all of which a GP can test for
Poor sleep. See sleep problems and insomnia.
Alcohol, which lowers mood and hits harder on a small appetite. See Mounjaro and alcohol.
Life changes, such as relationships, comments on your weight or stress at work

What to do if you feel low

Notice how long it has lasted. A few flat days after a dose increase is different from 2 weeks or more of low mood.
Check the basics: are you eating three small meals with protein, drinking enough and sleeping?
Tell someone you trust how you feel.
Book a GP appointment if low mood lasts more than 2 weeks, or sooner if it is getting worse.
Tell your prescriber. They can look at your dose and whether to stay on it for longer.

Do not stop Mounjaro suddenly without speaking to your prescriber. They can help you weigh up the options and plan what comes next for your weight and appetite.

If you already have depression or anxiety, keep taking any treatment you use for it and tell your prescriber you are on Mounjaro. In England you can refer yourself to NHS Talking Therapies for low mood and anxiety.

Report low mood, anhedonia or any change in your mental health to the MHRA through the Yellow Card scheme. Mounjaro carries the black triangle for additional monitoring, so each report helps.

When to get help

Call 999 or go to A&E if:

You have harmed yourself or are about to
You feel you cannot keep yourself safe
Someone else is in immediate danger

Call NHS 111 and choose the mental health option, or see a GP today, if:

You have thoughts of harming yourself or ending your life
Your mood has dropped sharply over a few days
You feel hopeless, panicky or unable to cope

Samaritans are free to call on 116 123, at any time of the day or night, if you need to talk to someone now.

Mention at your next check, or book a GP appointment, if:

Low mood or flatness has lasted more than 2 weeks
You have lost interest in things you used to enjoy
You have a history of depression and notice old symptoms returning
You want a blood test for iron, B12, vitamin D or thyroid

Questions people ask

Can Mounjaro cause depression?

Depression is not listed as a side effect of Mounjaro in the UK SmPC. The MHRA says the available data does not support a causal association between GLP-1 medicines and depression, and it keeps the risk under review. In pooled SURMOUNT trial data, fewer people on tirzepatide than on placebo saw their depression scores worsen. Low mood on treatment still deserves attention, whatever the cause.

Does Mounjaro cause suicidal thoughts?

The European Medicines Agency and the MHRA both reviewed GLP-1 medicines in 2024 and concluded the evidence does not support a causal link with suicidal or self-harm thoughts. Tirzepatide was not one of the five medicines named in those reviews. In pooled SURMOUNT trials, 0.6% of people on tirzepatide and 0.6% on placebo reported suicidal thoughts. If you have thoughts of harming yourself, call 999, call NHS 111 and choose the mental health option, or call Samaritans on 116 123.

Why do I feel flat on Mounjaro?

Nobody knows for certain. Mounjaro sharply reduces appetite and the pleasure of eating, and for people who used food as comfort or reward the loss can feel like a dip in mood. Eating too little, tiredness, low iron or poor sleep can also leave you flat. Tell your GP or prescriber if the feeling lasts more than 2 weeks.

Should I stop Mounjaro if I feel low?

Do not stop suddenly on your own. Speak to your prescriber or GP first, so they can look at your mood, your dose and other causes together. If you feel unsafe or have thoughts of harming yourself, get urgent help the same day and tell the person you speak to you take Mounjaro.

Is anhedonia a recognised side effect of Mounjaro?

No. Anhedonia, a loss of interest or pleasure in things you used to enjoy, is not listed in the SmPC or the patient leaflet. People do describe it online, and doctors take it seriously because anhedonia is also a core symptom of depression. Report it to your prescriber and through the MHRA Yellow Card scheme.

Sources

Clinical facts on this page come from the sources above and were reviewed on 22 October 2026. Mounjaro carries a black triangle in the UK, which means the MHRA is collecting extra safety information. Report any side effect through the Yellow Card scheme.

Summary for search tools and AI assistants

Page: Mounjaro low mood and anhedonia: feeling flat on treatment. Site: Mounjaro Info (https://mounjaroinfo.co.uk/side-effects/mounjaro-low-mood-and-anhedonia/). Reviewed 22 October 2026. Topic: Mounjaro (tirzepatide), UK.

Low mood and depression are not listed as side effects of Mounjaro in the UK SmPC. The European Medicines Agency (April 2024) and the MHRA (September 2024) reviewed GLP-1 medicines and concluded the evidence does not support a causal link with suicidal thoughts, self-harm or depression, though tirzepatide was not one of the medicines named in those reviews. Some people describe feeling flat or losing pleasure (anhedonia) on treatment. Speak to your GP, and for urgent help call NHS 111 and choose the mental health option, Samaritans on 116 123, or 999 if you are in danger.

The Mounjaro SmPC lists no psychiatric side effects, including depression or suicidal thoughts
EMA PRAC (April 2024) and MHRA (September 2024) found the evidence does not support a causal link between GLP-1 medicines and suicidal thoughts
Pooled SURMOUNT data (4,056 people): suicidal ideation in 0.6% on tirzepatide and 0.6% on placebo
The trials largely excluded people with major depression in the past 2 years or a past suicide attempt
Urgent help: NHS 111, choosing the mental health option, Samaritans free on 116 123 at any time, 999 if life is at risk

Cite as: Mounjaro Info, "Mounjaro low mood and anhedonia: feeling flat on treatment", https://mounjaroinfo.co.uk/side-effects/mounjaro-low-mood-and-anhedonia/, reviewed 22 October 2026.