The warning nobody reads aloud
There's a line in the GLP-1 paperwork about birth control that most people never get read to them. For women with PMOS (PCOS), it's the line that matters most.
A quick note before we start
We're writers, not doctors, and this is general information — not medical advice. Nothing here is a reason to start, stop, or change a medication or a contraceptive on your own. It's a nudge to ask a question at your next appointment. That's all. Carrying on.
Here is a sentence that should be said out loud in every appointment and almost never is: a GLP-1 medication can change how well your birth control works, and it can restart a fertility you'd quietly stopped planning around. Both of those things can be true for the same woman, in the same month, and nobody mentions either until it's a surprise.
We keep hearing versions of the same story. A woman with PMOS (PCOS) starts a GLP-1, her insulin settles, her cycles — dormant for years — come back. That's often a good and welcome thing. But "my periods came back" and "I could get pregnant now" are the same sentence, and the second half tends to arrive without warning.
The tirzepatide footnote
There's a genuine drug-interaction piece here, and it's specific. Tirzepatide (the medicine in Mounjaro and Zepbound) slows how quickly your stomach empties, and for a stretch after starting — and after each dose increase — that can reduce how much of an oral contraceptive your body absorbs. The manufacturer's own studies found the pill's absorption dropped by roughly 20% in that window. That's why the label advises using a barrier method, or switching to a non-oral form of birth control, for about four weeks after starting and after any dose bump.
Worth knowing: this appears to be largely a tirzepatide thing. Studies on semaglutide (Ozempic, Wegovy) haven't shown the same meaningful drop in contraceptive hormone levels. Different molecule, different footnote. Which is exactly the kind of detail that gets flattened into "GLP-1s" as if they were all one drug — they aren't.
"My periods came back" and "I could get pregnant now" are the same sentence.
Why the regulators spoke up
This isn't fringe. In mid-2025 the UK's medicines regulator, the MHRA, issued formal guidance urging women on GLP-1 medicines to use effective contraception, and stating plainly that these drugs should not be taken during pregnancy, right before trying to conceive, or while breastfeeding. The reason for the emphasis is the collision of two facts: the medicines aren't considered safe in pregnancy, and they can quietly make pregnancy more likely in the very women — those with PMOS (PCOS) and irregular cycles — who assumed it wasn't on the table.
What this looks like as a question, not a scare
We're not writing this to frighten anyone off a medication that's helping. We're writing it because "nobody told me" is a phrase we hear far too often, and it's avoidable. If you're on or starting a GLP-1, these are fair things to put to your clinician: Does the specific drug I'm on affect my contraception? Do I need a barrier or non-oral method for a few weeks after starting or increasing the dose? And — the one people skip — what's the plan if my cycles come back and pregnancy becomes possible again?
A provider who treats PMOS (PCOS) as a whole picture will raise this before you have to. If yours doesn't, that's useful information too. It's part of why we built the comparison — to make it easier to find people who see the whole woman, contraception footnote and all.
The quiet part
For some women reading this, the fertility surprise isn't a risk to manage — it's the thing they'd given up hoping for. We hold both of those at once: the woman guarding against an unplanned pregnancy and the woman stunned to learn one might be possible. Both deserve the sentence read aloud. Both deserve to hear it from a clinician, in an appointment, before it becomes a story that starts with "nobody told me."
The honest disclaimer. This is general information from the women who write Selene — not medical advice, not a recommendation, and not a promise of what will happen for you. Drug interactions, contraception, and fertility are individual and clinical; please make those decisions with a licensed clinician who knows your history, not with a website. Selene is editorial — we don't prescribe, sell, or dispense anything. GLP-1 medications are not FDA-approved specifically for PMOS (PCOS), and are not to be used in pregnancy.