Does Mounjaro stop the pill working?
Mounjaro (tirzepatide) can make the contraceptive pill less reliable, the MHRA says. If you take the pill, UK advice is to add condoms for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase, or switch to a non-oral method such as the coil or implant. The FSRH says Wegovy and Ozempic (semaglutide) don't need this.
- GLP‑1 medicines are prescription-only in the UK, not sold over the counter.6
- The MHRA says GLP‑1 medicines should not be taken during pregnancy, or by people who are breastfeeding.1
- The risks of these medicines are in Guide 5: Side effects and risks.
Why can Mounjaro make the pill less reliable?
Mounjaro slows how fast your stomach empties, and the MHRA says it may make the pill less effective in people who are overweight or obese.3,1
In a study, one 5 mg dose of Mounjaro cut the peak level of the pill's oestrogen (ethinyl estradiol) by 59%. Total exposure fell by 20%.3 The SmPC calls that single-dose drop "not considered clinically relevant". But it says there is limited information in women with obesity or overweight, so reduced effect "cannot be excluded".3 The FSRH, the UK body for contraception doctors (now called the College of Sexual and Reproductive Healthcare), says tirzepatide is the only GLP‑1 medicine found to have a clinically significant effect on the pill.5,1
What does UK advice say to do?
If you take the pill, add condoms for 4 weeks after starting Mounjaro and after each dose increase, or switch to a non-oral method.1,3,5
The MHRA, the UK leaflet and SmPC, and the FSRH all give this advice.1,4,3,5 The MHRA names the coil or implant as non-oral methods that are "more likely to be effective" with GLP‑1 medicines.1 The MHRA adds that not all methods work straight away, so check with a health professional or the leaflet when you switch.1
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What about Wegovy, Ozempic and other GLP-1 medicines?
The FSRH says there is no need to add condoms with semaglutide (Wegovy, Ozempic), liraglutide, dulaglutide, exenatide or lixisenatide.5
Vomiting and diarrhoea can still stop any pill being absorbed. The FSRH says to:5
- follow the missed-pill rules if you vomit within a few hours of a pill, or have severe diarrhoea for more than 24 hours
- think about a non-oral method if vomiting or diarrhoea keeps going
- use condoms consistently
What about emergency contraception and pregnancy?
The FSRH says the copper coil is the most effective emergency contraception; the MHRA says stop Mounjaro at least 1 month before trying for a baby.5,1
There is no direct evidence on GLP‑1 medicines and the emergency pill.5 The FSRH says a double dose of the levonorgestrel emergency pill should be considered if your BMI is over 26 or you weigh over 70 kg (11 st).5 For semaglutide, the MHRA gap before pregnancy is at least 2 months.1 The MHRA says women on these medicines must use effective contraception.2 More is in Contraception, pregnancy and GLP‑1s.
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Related questions
Sources
- MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know. Published 5 Jun 2025, updated 5 Feb 2026. gov.uk
- MHRA. Women on "skinny jabs" must use effective contraception, MHRA urges in latest guidance. Press release, 5 Jun 2025. gov.uk
- Eli Lilly. Mounjaro KwikPen (tirzepatide) UK summary of product characteristics (SmPC), date of revision 29 Aug 2026, sections 4.4, 4.5, 4.6, 6.3, 6.4 and 6.6. UK label. medicines.org.uk (emc)
- Eli Lilly. Mounjaro KwikPen (tirzepatide) UK patient information leaflet, last revised Aug 2026, sections 2, 3, 4 and 5. UK label. medicines.org.uk (emc)
- Faculty of Sexual and Reproductive Healthcare (FSRH) Clinical Effectiveness Unit. FSRH statement: glucagon-like peptide-1 (GLP-1) agonists and oral contraception. January 2025. Copy hosted by NHS Grampian. communitypharmacy.scot.nhs.uk (PDF)
- MHRA. First GLP-1 tablet for weight loss approved in the UK. Press release, 11 Jun 2026 ("As with all GLP-1 receptor agonists, this is a prescription-only medication"). gov.uk
Last checked 12 Oct 2026 · Next review due 12 Oct 2027 · Report an error
How this answer was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor before starting, stopping or changing any medicine. How we write