Does MJ interfere with HRT?

[twilightcafe]

I've been on HRT pills since Feb and MJ since Aug. Current up to the 5mg dose, which is working nicely.

Periods stopped. No PMT. Great.

Until yesterday. Now having an old-style bleed with flooding and bloated stomach.

I will speak to the GP when I come back from holiday but wondered if there is a link between HRT going wonky and Mounjaro.

Mounjaro does slow digestive transit I think, so possibly. Personally I don't find my digestive transit is any slower than usual so I'm not worried but I don't take oestrogen orally only progesterone and I've got a mirena for back up.

I had post menopausal bleeding about 4 months into starting MJ. All tests came back ok and the consultant put it down to MJ. I think it does interfere with oestrogen IIRC.

Yes it can do if you take oral progesterone. I would have had to either take a higher dose or have the Mirena coil, I opted for the coil to be safe.

You should tell your GP you are taking it so you can switch to patches or increase your dose of whatever pills you are taking.
https://springorchardsurgery.co.uk/news/glp-1-and-hrt-advice/

My doctor (who prescribes me MJ and HRT) says it does, yes. Every time I go up a dosage of MJ, I double the dose of my HRT progesterone pill for a month.

As MJ affects gastric functions, your oestrogen may 'overpower' your progesterone to give you a bleed if your progesterone is oral (layperson's understanding!)

Also, if you are taking oral contraceptive, you should use other methods for four weeks every time you kick up a dose.

I’ve been on HRT (oestrogel, oral progesterone and testosterone) for about 4 years and MJ for 10 months. No issues at all with my HRT even the oral progesterone. Everything working as it should.

ETA: Actually, yes @HelenDenver I was also told to increase my oral progesterone for a month when I increased my MJ dose but I’ve remained on 2.5mg so haven’t needed to.

My GP advised me to move to non oral HRT.

Yes it can if the HRT is oral. I have a Mirena patches and pessaries and the testosterone is a gel.

Yes, it can affect absorption which can be potentially harmful if oral progesterone isn't being absorbed properly. It can cause bleeding issues as you've discovered - you need to increase your progesterone dose or switch to a combined patch or try a Mirena coil.

Important Information for patients using the Weight Loss Medications Mounjaro® and Wegovy® and Oral Progesterones for Contraception or HRT – Five Valleys Medical Practice

Indeed it does - my GP was completely unaware of this and I only found out recently - I'm now off to the hospital for my uterus to be scanned this week as a result - they tried to blame my pharmacy who had sent them all my prescriptions - which they didnt read!

Every day's a school day. I didn't know there was such a link.

Can't get on with Mirena. Mine slipped too low in my womb due to fibroids. Got it removed in gynae outpatients with local anaesthetic (thank god).

Not enjoying periods. I never thought I'd be using sanpro again.

https://thebms.org.uk/wp-content/uploads/2025/05/23-BMS-TfC-Use-of-incretin-based-therapies-APRIL2025-E.pdf

https://www.pcwhs.co.uk/_userfiles/pages/files/resources/glp1_contraception_hrt_article.pdf

Your provider should have warned you of this when you declared your oral HRT when initiating treatment.

Links above talk about impact on oral progesterone and recommended solutions. My GP doubled my utrogestan.

My WLI prescriber advised me that MJ can basically interfere with any oral medication due to how much it slows digestion, and therefore impacting absorption of any oral meds. It was one of the reasons I went with wegovy, as although wegovy slows the system a little it's not as drastic an effect and I could still take oral contraception on wegovy, but not if I took mounjaro.

@Proteinpudding the oral contraceptive advice I had was to abstain/use condoms for four weeks after starting and after each dose change. Not that it would be permanently ineffective.

They may well have been aware, but the responsibility lies with the prescriber of the Mounjaro to inform you to seek guidance about your other meds, especially HRT and contraception.

Ah I wasn't told that, just that it would be ineffective with MJ and to make the choice of switching to an alternative method or choosing wegovy. Not sure if they were being over cautious.

The legal and clinical responsibility for checking interactions before prescribing falls on the private clinician/prescriber who issues your Mounjaro prescription.

Your GP was absolutely in the right.

@WeAllHaveWings - how does that work when the mounjaro is prescribed first? GP said that the increased progesterone would only have been for 4 weeks anyway? So when I reported taking HRT to the the pharmacy, I was already 4 weeks after starting the HRT so too late?

Didn't realise you started Mounjaro first. Your GP should have checked first when prescribing HRT or instructed you to discuss with your prescribing pharmacy if they didn't know.

When you informed your prescribing pharmacy they should have told you.

The guidelines for HRT with weight loss injections only came out in April 25. Most pharmacies informed their patients at that time and it should have been ongoing for new patients or any change of medications.