MHRA guidance published in June 2025 states that women of childbearing potential taking GLP-1 receptor agonists should use effective contraception, that these medicines should not be used in pregnancy, and that women taking tirzepatide (Mounjaro) should use a non-oral contraceptive — or add a barrier method — particularly while starting treatment or increasing the dose.
Why Tirzepatide Is Singled Out
Tirzepatide slows gastric emptying, and that can reduce how much of an oral contraceptive is absorbed. Less absorption means less protection. The effect is most pronounced around the time you start and around each dose increase, which is exactly when a patient is focused on managing nausea and least likely to be thinking about contraception.
The practical options are a non-oral method — the implant, an injection, an IUD or IUS, or a patch — or continuing the pill with a barrier method added during the relevant windows. Which is right for you is a conversation with a prescriber, not a decision to make from an article.
Why Pregnancy Matters Here
GLP-1 medicines are not recommended in pregnancy. Beyond the medicine itself, deliberate weight loss during pregnancy is not the goal of care, and these medicines are prescribed to produce exactly that.
There is a second effect that catches people out: weight loss can restore fertility in women who were not ovulating regularly, including many women with PCOS. People who had assumed they could not easily conceive sometimes find that assumption no longer holds a few months into treatment.
If you are planning a pregnancy, the standard advice is to stop the medicine well in advance and discuss timing with your prescriber. Semaglutide in particular has a long half-life, and clearance is not immediate.
The Online Questionnaire Problem
Much private weight-loss prescribing in the UK happens through online forms. Contraception questions are on those forms, but they are one item among dozens, easy to answer quickly and easy to answer as it was rather than as it is.
The GPhC has tightened what online pharmacies must do before supplying weight-management medicines, including independently verifying weight, height and BMI rather than accepting self-reported figures, and providing genuine two-way communication with a prescriber. A service that gives you no way to ask a question is falling short of what the regulator now expects.
If your contraception changes while you are on treatment — or if you switch from a pen to a tablet, or change dose — that is a reason to make contact rather than to carry on quietly.
What to Ask Before Starting
- Does my current contraceptive method interact with this specific medicine?
- If I am on the pill, what should I do during dose escalation?
- How long before trying to conceive should I stop?
- What should I do if I discover I am pregnant while taking it?
The last question deserves a direct answer before you need it: contact your prescriber promptly, and do not simply stop and say nothing.