Does GLP-1 Affect Mood? What UK Patients Should Know (October 2026)

01 · The short answer

Can GLP-1 affect your mood? The core answer

Can GLP-1 affect your mood? 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 does not mean your experience is irrelevant. People start these medicines at a point of big change: eating less, thinking about food differently, sometimes feeling unwell for a short time, and watching their body change. Any of these can colour how a person feels day to day. Whether the medicine itself plays a part is a question for your prescriber, who can look at your history, your other medicines and the current product information.

Describe what you notice, when it began and how it relates to your doses, and let a clinician weigh it up. If a symptom is suspected to be a side effect, you can report it yourself through the Yellow Card scheme.¹⁹

02 · Your next step

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

This question matters most if you already live with depression, anxiety or an eating disorder, or if you have had low mood in the past. It also matters if you are simply nervous about starting treatment and want to know what to watch for. In either case, the consultation is the right place to raise it. Be open about your mental health history. It helps the prescriber decide whether treatment is suitable and what follow-up you need.

If you are already taking a GLP-1 medicine and feel different, do not stop or change your dose on your own. Contact the prescriber who supplies it.

One practical idea is to keep a short note each week. Write down your mood, sleep, appetite and any side effects, and the day you injected. Patterns are much easier to discuss with a clinician than vague memories.

If you have thoughts of harming yourself, get medical help straight away.

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 guide: Does glp1 affect pregnancy.

03 · What the evidence says

What the evidence does and does not say

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

Regulators have also looked at this area. The European Medicines Agency's safety committee reviewed the evidence on GLP-1 medicines and suicidal thoughts and concluded in 2024 that it does not support a causal link.¹⁷ If it worries you, raise it in your consultation.

People who start a weight-management medicine are often also changing what they eat, how active they are and how they think about their body. Any shift in mood after starting treatment could come from the medicine, from those changes, from unrelated life events, or from a mix.

So the honest summary is this. It is a reasonable thing to ask about. The right response to a change is to report it, not to guess at the cause. You can report suspected side effects through the Yellow Card scheme, and doing so helps regulators build the picture for everyone.¹⁹

04 · How the medicine works

How Mounjaro works on appetite

To think clearly about mood, it helps to know what the medicine is designed to do. Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly. In the UK it is licensed for weight management in adults and for type 2 diabetes. It comes as a pre-filled multi-dose pen, the KwikPen, in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹

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. In practice, most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

Notice what that description contains. It is about appetite, stomach emptying and insulin response.

The dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide, which is sold as Wegovy and Ozempic.

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

05 · Why you might feel off

Why you might feel off on treatment

There is rarely a single answer, and a clinician is the right person to sort through it.

Start with the medicine's purpose. It is used alongside a reduced-calorie diet and increased physical activity.¹ That means starting treatment usually coincides with eating differently and moving more. If you feel flat or tired, ask yourself honestly whether you are eating enough regular, balanced meals, and raise it with your prescriber rather than pushing on.

Next, consider timing. If you notice that how you feel seems linked to the days after an injection or to a dose increase, write that down. It is precisely the kind of detail a prescriber can use.

Then there is the emotional side of changing body weight. Some people feel elated. Others feel anxious about how others respond, or unsettled that a long-standing part of their identity is shifting. Some feel disappointed if results are slower than hoped.

What should you not do? Do not double up, skip or change doses to try to manage how you feel, and do not adjust the medicine on advice from social media. Dose changes should come from your prescriber.

If you feel persistently low or unlike yourself, tell your prescriber. If you have thoughts of harming yourself, get medical help straight away.

06 · What to do if mood changes

What to do if your mood changes

If you notice a change in mood on a GLP-1 medicine, contact the prescriber who supplies it and describe what is happening. This is the single most useful step, and it applies whether you buy privately or receive treatment through the NHS.

Here is a practical sequence. First, note what you are feeling, when it started, and how it relates to your injection day and any recent dose increase. Second, check the patient information leaflet and the product information for your medicine, since they are the reference for recognised side effects and advice.¹¹³ Third, contact your prescriber.

Fourth, consider reporting through the Yellow Card scheme, run by the MHRA. You can report a suspected side effect yourself, and you do not need to be certain the medicine caused it.¹⁹ Reports help regulators spot patterns across many people.

What if it is an emergency? 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.

You may wonder whether to stop. That is a decision for you and your prescriber together. Tirzepatide takes roughly four to five weeks to clear the system after a final dose, and nothing needs doing while it clears, so stopping does not produce an instant change.¹ Whatever you decide, keep your prescriber informed so they can support you and record what happened.

You can also read about the Mounjaro-specific position in our guide to whether Mounjaro affects mood.

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

Individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.²

At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight.²

07 · Hormones and related questions

Hormones, menopause and other questions people ask

Does GLP-1 help with menopause, or menopause belly fat? Weight gain around menopause is common and driven by hormonal and metabolic change, which can make diet-only approaches slower; Mounjaro's eligibility criteria are the same at any adult age, and it can be prescribed alongside HRT, with no known interaction.

Does GLP-1 mess with your hormones? Tirzepatide acts on two gut-hormone receptors, GIP and GLP-1, which help regulate appetite, stomach emptying and the body's response to insulin.¹ Our separate guide on whether GLP-1 affects hormones goes into that question in more depth.

Periods, fertility and pregnancy are separate topics that matter to many readers. 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.

What about vision and other body systems? Our guide on whether GLP-1 affects eyesight covers that area. The principle is the same across all these questions.

If mood symptoms and hormonal changes overlap for you, as they often do around the menopause, mention both in your consultation.

08 · Safe use and storage

Safe use and staying well on treatment

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.

The MHRA publishes counterfeit medicine alerts and runs the Yellow Card scheme.⁷ Be wary of any seller offering to supply without a consultation or prescription, and check that a pharmacy is on the public register.

Storage is straightforward. Unopened pens are stored in the fridge, at 2–8°C, until first use, and they keep until the printed expiry date. Once you start using a pen, it can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. Do not use a pen that has been above 30°C or has been frozen. Follow the pen's instructions for each injection, and use the patient information leaflet as your reference.¹³ If you are unsure about anything on storage, ask us or your pharmacist rather than guessing.

If you take other medicines, including those for mood or anxiety, tell your prescriber so they can consider the whole picture. If you take insulin or sulfonylureas, doses may need adjusting because of the risk of low blood sugar. Do not change those yourself. Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. 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.

Looking after yourself in general helps too. Regular meals, activity you enjoy, decent sleep and people you can talk to all make treatment easier to live with. If something feels wrong, you do not need to wait for a scheduled review. Contact us, and report it through the Yellow Card scheme if you suspect a side effect.¹⁹

09 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Mounjaro must not be used during pregnancy. 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