Can Mounjaro Give You Mood Swings? (October 2026)

01 · The core answer

What the product information says about mood swings

Mood swings do not appear as a listed side effect of Mounjaro in the Summary of Product Characteristics or the patient information leaflet.¹¹³ It does not mean nobody ever feels different while on treatment. It means the licensing evidence does not list this as something the medicine is known to cause. 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 in 2024 that it does not support a causal link, and the MHRA keeps this under continuous review. 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.

Many pages blur the line between what a medicine is proven to do and what people say happened to them around the time they started it. A person starting Mounjaro is usually also changing what they eat, how they shop, how they socialise around food and how they see their body. Any of those can colour mood. Separating the medicine from the circumstances is the honest starting point.

Mounjaro is a once-weekly injection used alongside a reduced-calorie diet and increased physical activity. It is prescription-only and supplied after an online consultation reviewed by a GPhC-registered prescriber.¹ If you want a wider look at the topic, our guide on GLP-1 medicines and mood goes further.

02 · What to do next

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

This is relevant to you if you have started Mounjaro and feel more irritable, low, anxious or emotionally flat than before, or if you are worried about that before starting. The first step is to look at timing and context: did the change coincide with a dose increase, a big drop in how much you eat, poor sleep, a stressful event or a change in medicines? Jot down when you notice it. That note is useful to your prescriber.

The second step is to speak to a professional rather than sit with it. Tell the prescribing team or your GP about new or worsening mood symptoms. Do not stop or change a prescribed dose on your own, and do not use a different pen strength to see if it helps. Your prescriber can review the dose, your eating pattern and your other medicines, and can decide whether treatment should continue.

Thirdly, report it. The MHRA Yellow Card scheme lets patients and clinicians report suspected side effects, which helps regulators spot patterns.¹⁹ Reporting is sensible even if you are unsure the medicine is responsible.

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.

Related guides: Can mounjaro cause mood swings and Mounjaro side effects mood swings.

03 · Listed versus reported

Listed side effects versus what people report

A listed side effect is one the manufacturer and regulators have recognised in the product information after trials and monitoring. Mood swings are not in that category for Mounjaro.¹³

Online reports cannot tell us what caused a change. A person who posts that they felt emotional after an injection may also have been sleeping badly, eating far less, under pressure at work or going through a hormonal change. Online posts also over-represent people with strong experiences, and they say nothing about everyone who felt no difference.

This is also why the Yellow Card scheme exists. It is a structured route for reporting suspected reactions so that regulators can look for patterns across many reports, which is a very different thing from a single story online.¹⁹ If you believe your mood changed because of treatment, a report adds to that picture.

Your feelings are not imagined. Feeling different during a major change to your eating and body is common and entirely real. The cause is not established as the medicine itself, and the sensible response is to look at the whole picture with a clinician.

Medicine information is updated over time as new evidence emerges. The patient information leaflet in your box is the definitive guide to the list of effects for your pen, so read it and keep it. If something you experience is not in it, that is not a reason to ignore it; it is a reason to mention it to your prescriber.

04 · Eating less and mood

How eating less can affect how you feel

Mounjaro activates two gut-hormone receptors, 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.

That change in appetite is the intended effect, but it can be a big adjustment. Food is tied to routine, comfort, social life and stress relief. When the pull towards food quietens, some people feel relieved.

Eating much less can also affect energy, concentration and patience for anyone. If meals become small or irregular, you may feel more tired or short-tempered, in the same way that skipping meals affects most people. Planning regular, balanced meals and keeping to the diet advice your prescriber gives you is a practical way to protect how you feel day to day. Mounjaro works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

Social situations can be harder too. Skipping a favourite food at a family meal, being asked why you are eating less, or feeling judged about your weight can all bring up emotion. Some people find it helps to tell a trusted friend what they are doing and why.

If you notice that you are barely eating, cannot face food at all, or are using the medicine as a reason to restrict heavily, speak to your prescriber promptly. A good plan includes enough nourishment, and the prescribing team can review your dose and your eating pattern. Do not push on alone if food has become a source of distress.

If you have a history of difficulty with eating or body image, say so in your consultation and at every review. That information helps the prescriber decide whether treatment is right for you and how to support you through it.

05 · Weight change and body image

Weight loss, body image and emotions

Is it normal to have mood swings while losing weight? Emotional ups and downs during any significant weight loss are widely recognised, and they have many possible causes unrelated to the medicine. Changing shape, new feedback from other people and shifting expectations can all stir feelings.

In the SURMOUNT-1 trial, people taking tirzepatide alongside diet and exercise lost substantial weight over 72 weeks, compared with lifestyle changes alone.² These are trial averages, and individual results vary.

Some people feel a lift in confidence and energy. Others feel anxious about whether the loss will last, uneasy about how they look as they change, or frustrated if progress feels slower than they hoped. Compliments can feel awkward when you feel you were being judged before. Loose skin or a changing face can be hard to accept. None of this indicates a problem with the medicine; it reflects how closely body and self-image are connected.

Some practical ideas help many people. Focus on things other than the scales, such as stamina, sleep, how clothes fit and everyday mobility. Set expectations with your prescriber at the outset. Keep contact with friends and family rather than withdrawing. Do not compare your progress with other people, since trial averages do not predict your own result.

If your mood drops or you have distressing thoughts during treatment, seek help promptly.

Our guide on whether weight loss injections affect mood gives more background.

06 · Anger, irritability and personality

Anger, irritability and personality changes

Can Mounjaro cause anger issues, and does it affect personality? Neither anger problems nor personality change is listed as a side effect in the UK Mounjaro patient leaflet.

That said, feeling more irritable than usual is a recognisable human response to some of the circumstances around treatment. Eating less can leave you tired and short on patience. Poor sleep, which has many causes, can make small things feel bigger. Pressure to lose weight, worry about doing it right, or friction with a partner or colleague who comments on your eating can build tension.

Partners and family sometimes notice a change before you do, particularly if you are less interested in shared meals or treats. It can help to talk openly about what is happening so they do not take it personally, and to ask them what they have noticed. If others describe you as unlike yourself, take it seriously and mention it to your prescriber or GP.

A personality is not something a weekly injection is known to rewrite. But a sudden, marked change in behaviour, anger that feels out of character, or feeling unable to control reactions is worth professional attention whatever the cause. Do not wait for it to pass if it is damaging relationships or work; if you worry you might hurt yourself or someone else, get medical help straight away.

When you report this to a clinician, helpful details include when it started, how it relates to the timing of injections or dose changes, what you are eating, how you are sleeping, any new medicines or supplements, and any major life events. You can also submit a Yellow Card report if you suspect the medicine contributed.¹⁹

Never change the dose on your own or stop suddenly because of a hunch; your prescriber can weigh up the options with you. And if you feel unsafe at any point, get medical help straight away.

07 · Dopamine questions

Dopamine, cravings and the reward system

Does Mounjaro affect dopamine? The documented mechanism is activation of GIP and GLP-1 receptors, which help regulate appetite, slow how quickly the stomach empties, and improve the way the body responds to insulin.¹

You will see online articles that link GLP-1 medicines to reward pathways and cravings. If a page tells you that Mounjaro causes a dopamine crash or low dopamine, treat it with caution.

What many people do describe, in everyday terms, is that food seems less pressing. That fits with feeling fuller sooner and less hungry between meals.¹ Whether that quieter appetite feels like relief or like a loss of pleasure varies from person to person, and it is shaped by habits and emotions as much as by biology.

If you feel flat, unmotivated or unable to enjoy things you normally like, do not self-diagnose a neurotransmitter problem. Those feelings can come from low mood, stress, poor sleep, under-eating, illness and many other things. Ask your GP or prescriber, who can assess you properly and suggest what helps.

If you are struggling, speak to a clinician.

Symptoms like low energy, poor motivation or a flat mood are worth discussing with a professional rather than self-treating with supplements or unproven routines.

08 · Dose changes and timing

Dose increases, timing and keeping a diary

Mounjaro is started at a low dose and increased in steps, with pens in six strengths from 2.5mg to 15mg.¹ Many people notice that anything unusual in how they feel tends to be linked to a change, such as a new strength, a different week of the cycle or a run of unusual days. A simple diary can show whether there is a pattern.

Record the date of each injection, your strength, how you slept, what and roughly how much you ate, your energy, and a short note on mood. After a few weeks you may see that tough days follow poor sleep or skipped meals rather than the injection itself. Or you may see a pattern that you want to discuss with your prescriber. Either way, you will have something concrete to share, which makes the conversation more useful.

Do not adjust your own dose, delay an injection, or take extra doses to manage how you feel. Changes should come from your prescriber, who can review whether a step-up is right for you or whether you should stay longer at a strength. If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time; if more than 4 days have passed, skip it and take the next one on your normal day — never take two doses within 3 days of each other.

If you have stopped treatment, Mounjaro has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system, and nothing needs doing while it clears.¹ Some people notice appetite changes returning as it clears. If feelings are shifting around then, treat it as another thing to mention to your clinician rather than something to manage alone.

09 · Other medicines and health

Other medicines, conditions and things that can mimic mood effects

Many things can make you feel emotionally different during a period of change, and it is worth ruling them out. Other medicines can affect mood, so always tell your prescriber everything you take, including over-the-counter products and supplements. The consultation and the leaflet both ask for this for a reason.¹³

If you take insulin or sulfonylureas, doses may need adjusting because of the risk of low blood sugar, so your prescriber needs to know about them.¹ Shakiness, sweating or confusion can be signs of low blood sugar, so do not dismiss those symptoms; speak to your prescriber about them and about whether any change is needed.

Hormonal changes, thyroid problems, poor sleep, anxiety, depression, grief, work pressure and relationship difficulties can all affect mood and may overlap with starting treatment by coincidence. A GP can look at these. Do not assume the injection is to blame, and do not assume it is not; the right answer is to ask.

Alcohol, caffeine and irregular eating can add to feeling on edge. Tiredness is a frequent contributor, so protect your sleep where you can.

If you are unsure whether how you feel is connected to your treatment, start with the people who know your history. Our wider guide on whether weight loss drugs affect mood covers the class as a whole.

10 · Getting help and support

Getting help and who to contact

The right person to speak to depends on how urgent it feels. If you are in immediate danger or have thoughts of harming yourself, get medical help straight away: call 999 or go to A&E. Tell someone you trust. Do not wait for a pharmacy review.

For mood changes that are worrying but not urgent, contact your prescriber or your GP. Describe what has changed, when it began and how it affects your daily life. Bring your diary if you have kept one. The prescribing team can review your treatment and decide on next steps.

Report suspected side effects through the Yellow Card scheme, whether or not you are sure the medicine is the cause.¹⁹ You can do this yourself.

Whichever route you take, tell the prescriber about any history of mood problems, as this helps them judge suitability and plan support.

11 · 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