Does Mounjaro Affect Testosterone? (October 2026)

01 · The answer

Does Mounjaro affect testosterone? The honest short answer

Mounjaro is not described as a testosterone-altering medicine. Testosterone changes are not on the side-effect list in the UK patient leaflet, and the medicine works through gut-hormone receptors.¹¹³

The less firm part is the indirect question: if you lose a meaningful amount of weight on Mounjaro, could your hormone levels change as a result?

02 · Is it you?

Is this question relevant to you?

It is relevant if you already know you have a hormone condition, if you take testosterone or other hormone treatment, or if you have noticed new symptoms such as low mood, reduced sex drive or unusual tiredness since starting treatment. It is much less relevant if you are simply curious and feel well.

If you are in the first group, the practical step is to tell the prescriber reviewing your treatment. Our consultation is free and is reviewed by a GPhC-registered prescriber, and monthly reviews are part of ongoing care, so hormone history is exactly the sort of detail to put on the record. Do not stop or change any prescribed hormone treatment because of something you read on a website, including this one.

If you are in the second group, there is no reason from the product information to expect a testosterone problem from Mounjaro. If something new does appear, note when it started, how it behaves and whether it changes with your dose, and share that with a clinician rather than guessing at a cause.

03 · Next steps

What to do next

If you want a number rather than an opinion, ask your GP whether a blood test is appropriate for your symptoms. A test result, interpreted with your history, is the only reliable way to know your own levels. Symptoms alone cannot tell you, because many unrelated things produce the same complaints.

For wider background, see our weight loss clinic hub. If you take any hormone therapy, read our guide to combining testosterone with Mounjaro first and raise it with your prescriber before ordering.

If you notice anything you think may be a side effect, report it through the Yellow Card scheme.¹⁹ Reports are how regulators learn about effects that are not yet listed.

Related guide: Does mounjaro increase testosterone.

04 · What the product information says

What the UK product information says

The authoritative documents for any UK medicine are the Summary of Product Characteristics (SmPC) written for clinicians and the patient information leaflet written for you.¹¹³ For Mounjaro, neither lists lowered or raised testosterone as an established side effect.

It is worth being clear about what that statement means and does not mean. It does not mean that no individual could ever notice a change in how they feel, or that hormone levels never move for any reason while someone is on treatment. Many things can alter how you feel across a period of months: weight change, changes in eating, sleep, stress, other medicines and underlying health conditions. A medicine can be present during a change without being its cause, and the product information is written to describe what the medicine itself is established to do.

Testosterone changes are not listed as a side effect in the UK patient leaflet, and new symptoms deserve a conversation with a clinician.

The leaflet also tells you what to do if you get side effects: speak to your doctor, pharmacist or nurse, including about effects not listed in the leaflet, and you can report them yourself through the Yellow Card scheme.¹⁹ If you have a symptom that worries you, that route matters more than any web search.

In practice, when you read a claim about Mounjaro and a hormone, ask where it comes from. Is it the product information, a published trial, or an opinion?

05 · How Mounjaro works

How Mounjaro works and why that matters for hormones

Mounjaro contains tirzepatide, which is described as the first treatment of its kind to activate two natural gut-hormone receptors at once: GIP and GLP-1.¹ 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.

Notice what that description contains: appetite, stomach emptying and insulin response.

A practical consequence of how the medicine works is the timeline. 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.¹ There is no way to speed this up, and nothing needs doing while it clears.

This mechanism also explains why Mounjaro is licensed for weight management in adults and for type 2 diabetes, not for any hormonal condition. Hormone conditions have their own assessment and treatment routes, which your GP or a specialist will guide.

06 · Weight loss and hormones

Weight loss and hormones

The most common claim you will meet is that losing weight with Mounjaro improves testosterone in men and eases high testosterone in women.

The headline trial, SURMOUNT-1, looked at weight. 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. Those results are about body weight. They are not results about testosterone, and they should not be read as such.

There is also a reason for caution in the other direction. Fatigue, low drive and irritability are common complaints with many causes. If you feel unwell on treatment, do not assume it is a testosterone problem and do not assume it is nothing. Tell your prescriber, who can review your dose, your eating and your wider health.

Trial headlines tell you about weight, not hormones, and personal hormone effects can only be established by testing you, with your history in mind.

07 · Men and symptoms

Men: low libido, erections and tiredness

These are reasonable questions, and the honest answer starts with the fact that these symptoms are common and have a long list of possible causes.

Those causes include stress, poor sleep, anxiety, low mood, alcohol, smoking, other medicines, circulation and heart health, diabetes and hormone levels. Testosterone is only one possibility, and a low level is not always the reason even when symptoms are present. This is why we advise a proper assessment rather than self-diagnosis. A GP can ask about your symptoms, examine you where needed, and arrange appropriate tests.

If you notice a change in erections or desire after starting treatment, tell your prescriber and consider reporting it through the Yellow Card scheme.¹⁹ Describe the timing, because whether a symptom began before treatment, soon after a dose change, or gradually can all help a clinician think it through.

Erection difficulties deserve a proper check rather than a quick fix. Our page on Mounjaro and circulation covers how circulation fits into the picture. Avoid buying unregulated pills or powders advertised for erections or testosterone; products offered without a consultation or prescription carry real risks, and a regulated clinician can recommend what is appropriate.

Changes in confidence, body image, energy and mood often accompany weight loss, and any of these could play a part. If a change in drive concerns you in either direction, it is a legitimate thing to discuss with a clinician.

08 · Women, PCOS and contraception

Women: PCOS, periods and contraception

If you have polycystic ovary syndrome or changes in your periods, raise it with your prescriber or GP.

Symptoms such as irregular periods or excess hair growth have their own routes of assessment through your GP, and they should not be managed by guesswork. Weight is one of several factors clinicians consider in such conditions, but how it applies to you is individual.

Mounjaro can reduce the absorption of oral contraceptives because it slows how quickly the stomach empties.⁷ 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.¹ This is a practical consideration unrelated to testosterone, but it is the hormone-adjacent fact that most directly affects many women.

Changes to periods, spotting or unusual bleeding while on treatment should be raised with a clinician, not assumed to be harmless or assumed to be a testosterone effect. 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.

Our guide on Mounjaro and fibroids covers another question that often arises. As ever, report any suspected side effect through the Yellow Card scheme so that regulators can learn from it.¹⁹

09 · Testosterone treatment alongside

Taking testosterone treatment alongside Mounjaro

If you are prescribed testosterone, or are thinking about it, the key rule is disclosure. Tell the prescriber reviewing your Mounjaro treatment about every medicine you take, and tell whoever manages your hormone treatment that you are using or considering Mounjaro. Neither team can make good decisions on half the picture.

That is not the same as saying there is nothing to discuss. Your prescriber will look at your overall health, your other medicines and your goals, and can advise whether the combination suits you and how it should be monitored. Our guide on combining testosterone with Mounjaro goes into the practical questions to ask.

Do not buy testosterone, peptides or so-called hormone boosters from unregulated sellers, including those offering to supply without a consultation or prescription. Such products may be counterfeit or of unknown strength, and you would have no clinical oversight if something went wrong. If you want hormone treatment, it should come through a regulated clinician who has assessed you and who monitors you afterwards.

Equally, do not stop a prescribed medicine on your own initiative because of something on the internet. If you are worried about how two treatments fit together, ask. Our team provides ongoing monthly reviews, dose-titration and follow-up assessments, as well as side-effect support, and repeat orders re-check suitability, with no auto-shipping.

One further point on honesty: some online sellers present Mounjaro as a hormone fix or pair it with other products with dramatic claims. Mounjaro is licensed for weight management in adults and for type 2 diabetes, used alongside a reduced-calorie diet and increased physical activity.¹ Any seller promising hormone benefits is going beyond the product information, and that should make you more cautious, not less.

10 · Testing and monitoring

Testing, symptoms and when to see your GP

If you are worried about your testosterone, the reliable route is a clinical assessment and, where your GP thinks it appropriate, a blood test. Signs people often associate with low testosterone include reduced sex drive, tiredness and low mood, but none of these proves a hormone problem on its own, because the same symptoms occur with many other conditions.

When you see a clinician, it helps to bring a short, clear account. Say when the symptoms started, whether they began before or after Mounjaro, whether they have changed with a dose increase, what else has changed in your life, and what other medicines you take. Mention any weight change, any change in eating and any difficulty sleeping. A well-organised history often tells a clinician more than a single test.

Ask whether the timing of a blood test matters. Follow the guidance you are given.

You may also see questions about the side effects of testosterone treatment itself. Those depend on the preparation and your health, and your prescriber of that treatment is the right person to explain them. If you are using testosterone and Mounjaro together, make sure both prescribers know, and report anything you suspect is a side effect through the Yellow Card scheme.¹⁹

Get medical help straight away for chest pain, difficulty breathing, swelling of the face, lips, tongue or throat, or any severe or sudden symptom that frightens you. This page is information, not a substitute for medical advice, and a prescription-only medicine such as Mounjaro is supplied only after an online consultation reviewed by a GPhC-registered prescriber.

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

12 · NHS and private access

NHS and private access to Mounjaro

Mounjaro is available on the NHS, but access is being phased in over several years.⁴⁶ NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first (initially BMI 40+ with four or more qualifying conditions). Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

If you have a hormone condition, your NHS clinicians may already be involved in your care, and they are a good place to start for questions about testosterone. They can also advise on whether you fall into a group prioritised for NHS treatment.

For private treatment, our process is straightforward. You complete a free online consultation, a GPhC-registered prescriber reviews it, and if the prescriber decides treatment is not suitable, the order is refunded automatically in full. Approved orders are dispensed by our registered pharmacy (GPhC 9012878), with same-day dispatch when ordered by 3pm and free next-day tracked delivery in temperature-controlled packaging. Supply is official LillyDirect supply, and the price shown is the price paid.

Whichever route you choose, the expectations are the same. Mounjaro is used alongside a reduced-calorie diet and increased physical activity, and individual results vary. The trial figures describe weight loss, not hormone change, so if hormones are your reason for asking, raise that directly with your prescriber at the start. Tell them about any existing hormone diagnosis or treatment, and keep them updated as treatment goes on.