Does Mounjaro Increase Testosterone? (October 2026)

01 · The core answer

Does Mounjaro increase testosterone?

Mounjaro is not licensed to raise testosterone, and testosterone is not listed as a side effect in the UK Mounjaro patient leaflet. Tell your prescriber about any new or lasting symptom.¹³ The medicine is tirzepatide. It activates the GIP and GLP-1 gut-hormone receptors, which help regulate appetite, slow how quickly the stomach empties and improve the way the body responds to insulin.¹

Mounjaro is a weight-management and type 2 diabetes treatment. It is not a hormone therapy, it is not licensed for low testosterone, and nobody should start it in order to raise testosterone.

The same applies in the opposite direction. The leaflet does not list a lowering of testosterone either.

02 · Is this relevant to you?

Is this relevant to you?

This question matters most if you are a man considering weight-loss treatment and are worried about your hormones, or if you are already on treatment and have noticed a change you cannot explain. In either case the useful step is a conversation with a clinician.

If you are already on treatment, tell the prescriber reviewing it about any new symptom, with the date it started and any dose change around that time. If you suspect a hormone problem, speak to your GP, who can assess you properly in light of your history and your medicines.

If you want to report something you think may be linked to the medicine, you can use the MHRA Yellow Card scheme.¹⁹

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

03 · What to do next

What to do next

The sensible next step depends on where you are. If you are worried about low testosterone, speak to your GP and mention any medicines you take. If you are on Mounjaro and have a symptom that is new or does not settle, tell your prescriber and check the patient leaflet. If you would like to talk about treatment for weight, a free online consultation at our weight loss clinic is reviewed by a GPhC-registered prescriber.

Mounjaro (tirzepatide) 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. Individual results vary. This page is information, not a substitute for medical advice.

Related guides: Does mounjaro affect testosterone and Glp 1 and testosterone and Does mounjaro lower testosterone.

04 · What the leaflet lists

Testosterone and the Mounjaro patient leaflet

Testosterone is not listed as a side effect in the UK Mounjaro patient leaflet; tell your prescriber about any new or lasting symptom.¹³ The patient leaflet is the first place to check when you wonder whether a change might be linked to treatment, and it is written for everyone who uses the medicine rather than for any single person.

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 (KwikPen) in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹ Neither licensed use is the treatment of a hormone deficiency.

It helps to keep three ideas apart. The first is what the medicine is licensed to do, which is help with weight management and type 2 diabetes. The second is the list of side effects in the leaflet, which are mostly digestive. The third is what happens to an individual person during treatment, which depends on their own health and circumstances and is best discussed with a clinician who knows them.

If a symptom worries you, describe it to your prescriber in plain words. Say when it began, whether it followed a dose change, and what other medicines you take. That is far more useful than a general sense that something feels different, and it lets the prescriber decide what to do next.

05 · How Mounjaro works

How Mounjaro works

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

If you have questions about any other hormone in your own body, speak to your GP.

This dual action is what distinguishes Mounjaro from single-action GLP-1 medicines such as semaglutide (Wegovy/Ozempic).¹ Each medicine has its own product information and its own leaflet, so what applies to one should not be assumed to apply to another.

There is also a practical point about timing. Tirzepatide has a half-life of about five days, so after a final dose it takes roughly 4–5 weeks to clear the system — there is no way to speed this up, and nothing needs doing while it clears.¹ Because the medicine stays in your system for some time after your last dose, a clinician is the right person to help you make sense of how you feel after stopping.

06 · Weight-loss trial results

What the weight-loss trial measured

The main trial evidence for Mounjaro describes weight, and it is worth reading carefully for what it does and does not measure. 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

These are trial averages — individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.² Trial averages do not predict your own result.

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

Those are the outcomes described. They concern body weight, and they should not be stretched to suggest more than they show. If you are asking about your own hormone levels, speak to your GP.

It also helps to keep a simple written record as treatment goes on. Note when you started, when any dose changed and when any symptom began. A written timeline lets a clinician judge whether a change lines up with treatment, with a different medicine or with something else in your life.

If your goal is weight loss, the route the trial describes is to use the medicine alongside a reduced-calorie diet and increased physical activity, and to review progress with your prescriber. A concern about low testosterone deserves its own assessment with your GP.

07 · Worried about low testosterone

Worried about low testosterone? Start with your GP

If you think your testosterone may be low, the right step is to speak to your GP rather than to use a medicine that is licensed for something else. Mounjaro is not licensed for that purpose, and it should not be started or stopped as a way of testing the idea.

Your GP can listen to your symptoms, consider other explanations and decide what, if anything, needs doing next. That conversation is worth more than an internet checklist, which can either alarm or falsely reassure.

Always share your full medical history and medicine list during consultation, both with your GP and with the prescriber reviewing your Mounjaro treatment.¹³

Some practical suggestions apply whatever the cause:

• Write down what you notice and when it began, relative to your start date or any dose change.
• Mention every other medicine you take, including anything bought without a prescription.
• Ask for anything you do not understand to be explained in plain language.
• Do not stop prescribed treatment without discussing it with your prescriber.

You may see products marketed to men as testosterone boosters, along with lists of foods, drinks and quick routines. None of these is part of Mounjaro treatment. If you are thinking of using a supplement alongside treatment, check with a pharmacist first. Low-cost supplements are available without assessment, with no clinical oversight, and dosing is not standardised.

If you have any unusual results or findings from your GP, share them with the prescriber reviewing your Mounjaro treatment.

08 · Tell your prescriber everything

Tell your prescriber about all your medicines

If you use any other medicine, including a prescribed testosterone treatment, tell the prescriber reviewing your Mounjaro about it. Always share your full medical history and medicine list during consultation.¹³

Your GP, any specialist who prescribes your other medicines and the prescriber reviewing your Mounjaro should all be working from the same medicines list. Keep an up-to-date list of everything you take, with names, strengths and how often you use each one, and bring it to every appointment.

For more on this, see our guide on using Mounjaro and testosterone together.

Do not change the dose or timing of any medicine on your own because you have started another one, and do not change your treatment because of something you have read. Decisions like these belong with the clinicians who know you.

09 · Who should not take it

Who should not take Mounjaro

Mounjaro is not suitable for everyone. You should not take it if you are allergic to tirzepatide or any of its ingredients, and it should not be used during pregnancy or while trying to conceive.¹³ 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.¹³

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.¹³ If you are thinking about a family, raise your plans early with your prescriber.

Mounjaro slows stomach emptying, which can reduce how well oral contraceptive pills are absorbed. The advice is to switch to a non-oral method, or add a barrier method (such as condoms), for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. This applies to the pill only — implants, coils and injections are unaffected.¹

Always share your full medical history and medicine list during consultation, so that the prescriber can judge whether treatment is suitable for you.

10 · Side effects and reporting

New symptoms on Mounjaro: what to do and how to report

If you notice a new or lasting symptom, tell your prescriber and, where you think the medicine may be involved, report it through the Yellow Card scheme.¹⁹ Testosterone is not listed as a side effect in the UK Mounjaro patient leaflet.

Like all medicines, Mounjaro can cause side effects, and most are digestive. The most common — affecting more than 1 in 10 people — are nausea, diarrhoea, vomiting, constipation and abdominal discomfort. Common effects (up to 1 in 10) include indigestion, reduced appetite, dizziness, reflux, burping, hair shedding and injection-site reactions. Side effects are most likely when starting treatment or moving up a dose, and for most people they ease within days to a few weeks as the body adjusts.¹³

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.¹³ Get medical help straight away, or go to A&E, if you have any of those warning signs.

A sensible approach to any other new symptom is:

• Check the patient leaflet to see whether it is already listed.
• Tell your prescriber, with the date it began and any recent dose change.
• Speak to your GP about anything that worries you or does not settle.
• Report through Yellow Card if you think the medicine may be involved.

A clear description of what you experienced, when it started and what else you were taking is enough for a report. You do not need to prove a link.