Independent UK medicine guidance
Mounjaro and contraception: does it affect the pill?
If you have overweight or obesity and take an oral contraceptive, current Mounjaro guidance advises additional precautions after starting treatment and after every dose increase. This guide explains the four-week rule, why it exists, and what to do if you vomit or have diarrhoea.
Non-oral methods include options such as the implant, injection, coil, patch or vaginal ring, although suitability and the time each method takes to become effective vary. Discuss the right choice with a pharmacist, GP or sexual-health professional.
Why may Mounjaro affect the pill?
Tirzepatide delays gastric emptying. Studies found that a single 5mg dose reduced the peak concentrations and delayed the absorption of components of a combined oral contraceptive.
There is limited information about what this means for contraceptive effectiveness in women with overweight or obesity. Reduced effectiveness cannot be ruled out, which is why the four-week precaution is recommended.
The precaution applies again after every dose increase, not just when treatment first begins.
What if you vomit or have diarrhoea?
Vomiting or severe diarrhoea can independently prevent an oral contraceptive from being absorbed properly.
Follow the missed-pill or sickness instructions supplied with your contraceptive. Seek advice from a pharmacist or sexual-health service if you are uncertain, particularly if you have had unprotected sex.
Emergency contraception may be time-sensitive, so do not wait for your next routine appointment.
Pregnancy and Mounjaro
Mounjaro should not be used during pregnancy. If you think you may be pregnant, contact a healthcare professional promptly.
If you are planning a pregnancy, current product information says tirzepatide should be discontinued at least one month beforehand. Arrange this with your prescriber, especially if you use it for diabetes.
Do not rely on weight loss, irregular periods or reduced fertility as contraception. Fertility may increase for some people as weight and metabolic health change.
Common questions
Does Mounjaro stop the pill working?
Current guidance advises extra precautions rather than stating the pill stops working. If you have overweight or obesity and take an oral contraceptive, either add a barrier method such as condoms for four weeks after starting Mounjaro and four weeks after every dose increase, or switch to a suitable non-oral method.
Why does the four-week rule apply after every dose increase?
Tirzepatide delays gastric emptying, and studies found a single 5mg dose reduced peak concentrations and delayed absorption of components of a combined oral contraceptive. Because reduced effectiveness cannot be ruled out, the precaution is repeated after each dose increase, not only at the start of treatment.
Can I take Mounjaro while trying to conceive?
Mounjaro should not be used during pregnancy. If you are planning a pregnancy, current product information says tirzepatide should be discontinued at least one month beforehand, arranged with your prescriber. Do not rely on weight loss, irregular periods or reduced fertility as contraception, as fertility may increase as weight and metabolic health change.
Related guides
Sources: Mounjaro Summary of Product Characteristics (eMC) • MHRA GLP-1 contraception guidance • NHS tirzepatide guidance
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