Mounjaro Male Fertility: What We Know and Don't (October 2026)

01 · The core answer

Does Mounjaro affect male fertility?

Nothing in the UK product information lists reduced fertility, lower sperm count or altered semen quality as an effect of Mounjaro.¹¹³ It is not listed as a side effect in the UK patient leaflet.

The absence of a listed effect is not a study showing sperm are unaffected. Claims of a firm benefit or a firm harm to sperm are not supported by the UK product information.

02 · Your decision

What should you do if you are planning a family?

Tell your prescriber at the start of the consultation, and tell any fertility clinic you attend. Mounjaro is a prescription-only medicine supplied after an online consultation reviewed by a GPhC-registered prescriber, so the conversation is part of the normal process.¹ Our weight loss clinic team can discuss timing with you.

03 · What the label says

What the UK label says about fertility

Male infertility and sperm changes are not among the listed effects.¹¹³

For any symptom or effect that is not listed, the sensible steps are the same. Discuss it with your prescriber, and report it through the Yellow Card scheme.¹⁹

For wider reading, see our overview of Mounjaro's effects on fertility and the guide to male side effects of Mounjaro.

04 · How it works

How tirzepatide works and why that matters here

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.¹

Tirzepatide activates 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 Reproductive hormones are not part of how the label describes tirzepatide working.

Our guide to GLP-1 medicines and male fertility looks at the wider drug class.

05 · Weight and fertility

Weight loss and fertility

Mounjaro's proven effect is on body weight. 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 and individual results vary.

Any fertility benefit from weight loss would be an indirect possibility, not a promise, and it is not a licensed reason to take the medicine.

The question of whether it might help is covered in does Mounjaro help with fertility and does Mounjaro increase fertility. Both are worth reading with the same caution.

06 · Pregnancy and partners

Pregnancy, conception and partners

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.¹

This advice is for the person who could become pregnant. It does not say what a man taking Mounjaro should do while his partner tries to conceive. Ask your prescriber about timing for your own case.

If a woman is taking Mounjaro, contraception matters. 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. This applies to the pill only; implants, coils and injections are unaffected.¹⁷

07 · Stopping treatment

If you decide to stop before trying for a baby

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

Stopping is a decision to make with your prescriber rather than alone. Our team provides ongoing monthly reviews, and repeat orders re-check suitability with no auto-shipping. You can tell us about fertility plans at any review, and we will adjust the plan around them.

08 · 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

09 · NHS and private routes

NHS and private access

Mounjaro is available on the NHS, but access is being phased in over several years. 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).⁴⁶ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment.

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.