The MHRA advises that Mounjaro may reduce the effectiveness of oral contraceptives in people with overweight or obesity. If you use an oral contraceptive, you should switch to a non-oral method or add a barrier method such as condoms for four weeks after starting Mounjaro and for four weeks after every dose increase. Because Mounjaro doses usually go up every four weeks, these periods run back to back for several months. The advice is specific to Mounjaro; it does not apply to Wegovy in the MHRA guidance, although Foundayo carries its own similar precaution. All GLP-1 medicines should be avoided in pregnancy, so effective contraception matters throughout treatment.
In guidance published in June 2025, the MHRA reminded women that GLP-1 medicines, including semaglutide, liraglutide and tirzepatide, should not be used during pregnancy, just before trying to conceive, or while breastfeeding, because there is not enough safety data to know whether they could harm a baby. It advised women of childbearing potential to use effective contraception throughout treatment.
For Mounjaro specifically, it added a further precaution: tirzepatide may reduce the effectiveness of oral contraceptives in people who have overweight or obesity. Anyone using an oral contraceptive should therefore use a non-oral method (such as the coil or implant) or add a barrier method (such as condoms) for four weeks after starting Mounjaro and for four weeks after any increase in dose. This advice is already included in the patient information leaflet supplied with Mounjaro.
Worth knowing
The regulator's concern is reduced absorption of contraceptive hormones, not a harmful chemical reaction. The combination isn't dangerous in itself; the risk is that your pill may be less protective than you expect.
Mounjaro slows how quickly food and medicines leave your stomach, which is part of how it reduces appetite. An oral contraceptive relies on being absorbed steadily from the gut, so when stomach emptying is delayed, the amount of hormone reaching your bloodstream can be lower or delayed. This effect is greatest after the first dose and after a dose increase, and tends to fade as your body adjusts, which is why the precaution applies to those specific windows rather than the whole of your treatment.
When the Precaution AppliesMounjaro is started at a low dose and increased in steps, usually no faster than every four weeks, up to a maximum of 15mg (see our Mounjaro dose schedule guide). Each step is a new dose increase, which means each one brings a new four-week precaution window. In practice, if your dose rises every four weeks, you'll need extra protection more or less continuously for the first several months, ending four weeks after your final increase.
Illustration only, assuming your dose rises every four weeks all the way to 15mg. Your own schedule may be slower, and may stop at a lower dose, so follow your prescriber's plan and count four weeks from each actual dose change.
| Stage | Dose | Extra protection needed? |
|---|---|---|
| Starting Mounjaro | 2.5mg | Yes, for 4 weeks after the first dose |
| First increase | 5mg | Yes, for 4 weeks after the increase |
| Further increases | 7.5mg, 10mg, 12.5mg, 15mg | Yes, for 4 weeks after each increase |
| Stable on a dose | Any dose, no recent change | No further precaution from Mounjaro itself |
| Holding at a dose for longer | Your prescriber may slow your increases | The windows follow your actual dose changes |
Important
The four-week clock restarts with every dose increase. If your prescriber changes your dose, treat that day as the start of a new four-week precaution period.
Only methods that rely on absorption through your digestive system are of concern. Methods that don't pass through the gut are not affected by Mounjaro's effect on stomach emptying.
| Method | Relies on gut absorption? | During the 4-week windows |
|---|---|---|
| Combined pill | Yes | Switch to a non-oral method or add condoms |
| Progestogen-only pill | Yes | Switch to a non-oral method or add condoms |
| Contraceptive patch or vaginal ring | No | Not affected by delayed stomach emptying |
| Contraceptive injection | No | Not affected by delayed stomach emptying |
| Implant, coil (IUD) or IUS | No | Not affected by delayed stomach emptying |
| Condoms | No | Suitable as the added barrier method |
If you would rather not add condoms for months on end, many people choose to move to a long-acting non-oral method, such as the implant or coil, for the duration of treatment. That is a decision to make with your GP or a sexual health clinic, who can also advise on contraception that suits your circumstances.
Vomiting and Diarrhoea Can Matter TooSeparately from Mounjaro's effect on absorption, severe vomiting or diarrhoea can reduce how well any contraceptive pill works, whatever medicine you are on. Because nausea, vomiting and diarrhoea are among the most common Mounjaro side effects, especially after dose increases, it's worth reading the missed-pill advice in your pill's leaflet and following it if you are unwell. Our Mounjaro side effects guide covers how to manage these symptoms, and our Mounjaro tolerance guide explains how your body adapts to each dose. Eating small, gentle meals and keeping up fluids, as set out in our nutrition guide, can help you stay well.
How Mounjaro Compares With Other GLP-1 Treatments| Treatment | Oral contraceptive precaution | Notes |
|---|---|---|
| Mounjaro (tirzepatide) | Non-oral or barrier method for 4 weeks after starting and after each dose increase | MHRA advice applies specifically to Mounjaro |
| Foundayo (orforglipron) | A similar precaution, around 30 days after starting and after each dose increase | See the Foundayo side effects guide and dosage guide for timings |
| Wegovy injection and Wegovy pill (semaglutide) | No specific oral contraceptive precaution in the MHRA guidance | Effective contraception is still advised on any GLP-1 medicine |
If you are considering switching between treatments, remember that a new medicine or a new dose schedule can bring its own precaution period, so factor your contraception into any switch. Our guides to Mounjaro vs Wegovy, Foundayo vs Mounjaro and the Mounjaro, Wegovy and Wegovy pill decision guide can help you weigh the options.
Because there isn't enough safety data in pregnancy, the MHRA advises stopping GLP-1 medicines before trying to conceive. For tirzepatide (Mounjaro), it advises waiting at least one month after stopping before trying to get pregnant; for semaglutide (Wegovy), at least two months. The UK product information for Foundayo advises stopping at least three weeks before a planned pregnancy because of how long the medicine takes to leave your body. Weight loss can also improve fertility, particularly for women with conditions such as PCOS, so some women find they are more likely to conceive than before treatment. If you are planning a pregnancy, or think you might be pregnant, speak to your prescriber promptly; our guides to Mounjaro and PCOS, Wegovy and PCOS and Foundayo and PCOS cover the fertility considerations in more detail.
| Situation | What the guidance advises |
|---|---|
| Not planning a pregnancy | Use effective contraception throughout treatment, with extra protection during Mounjaro's precaution windows |
| Planning to conceive | Stop the medicine before trying: at least 1 month for tirzepatide, at least 2 months for semaglutide, at least 3 weeks for orforglipron (Foundayo) |
| Think you may be pregnant | Contact your prescriber promptly and don't take further doses until you have advice |
| Breastfeeding | GLP-1 medicines are not recommended while breastfeeding |
Hormonal life stages can also affect how you feel on treatment. Our guides to Mounjaro and menopause, Mounjaro for women over 40, Wegovy for women over 40 and Foundayo for women over 40 look at contraception and treatment in the years around perimenopause.
What to Do If You Think Protection May Have FailedIf you have had unprotected sex, or your pill may not have been protective during a precaution window, emergency contraception is available from pharmacies and sexual health services, and is most effective the sooner it is taken. If your period is late, take a pregnancy test and contact your prescriber. Your pharmacist can advise you confidentially on the options that are appropriate alongside your treatment.
A Practical Checklist Before You Start- Tell your prescriber which contraception you use, including any pill, patch, ring or implant, and any plans for a pregnancy in the next year
- Decide in advance whether you'll switch to a non-oral method or add condoms, so you're protected from your very first dose
- Put the date of every dose increase in your diary, and count four weeks forward from each one as a precaution period
- Keep a supply of condoms to hand during titration, since your dose steps can arrive before you've planned for them
- Re-check your plan if you switch medicines, change dose, or are unwell with vomiting or diarrhoea
Building these small habits into your routine at the start makes it far easier to stay protected without having to think about it each week, and means you can concentrate on the reason you started treatment in the first place. If you're not sure whether you're eligible to start, our BMI calculator and guide to NHS eligibility are a good place to begin.
Questions About Contraception and Your Treatment?
Our GPhC-registered pharmacy team can talk through your contraception, other medicines and any pregnancy plans as part of your consultation.
Start Your Free Online Consultation → Happy Pharmacy is a GPhC-registered pharmacy (No. 9013192) — Superintendent Pharmacist: Palvinder Deol — Rated 4.8★ Excellent on Trustpilot- MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know. Guidance, published 5 June 2025, updated 12 June 2025.
- GOV.UK. Women on skinny jabs must use effective contraception, MHRA urges in latest guidance. Press release, June 2025.
- The Pharmaceutical Journal. MHRA urges women taking weight-loss drugs to use effective contraception. 5 June 2025.
- Mounjaro® (tirzepatide) UK Summary of Product Characteristics and Patient Information Leaflet.
- Foundayo® (orforglipron) UK Summary of Product Characteristics, electronic Medicines Compendium (emc), August 2026.