Weight Loss Medication and Hormones

The group of drugs known as GLP-1 receptor agonists, including Mounjaro® (tirzepatide) and Wegovy® (semaglutide), have become more commonly used in recent years. They are primarily used to help manage diabetes and are also licensed for weight loss. Increasingly, patients are prescribed these injections through private companies. As many of our patients are accessing these injections online, and we aren’t always informed, we are making sure that all women who are using, or may use contraception or HRT in the future, are aware of the interaction. If you are accessing it privately, the prescribing clinician should have already counselled you appropriately about this, and it is important that you discuss your repeat medications with them directly.

One of the ways GLP1s work is by slowing down the emptying of your stomach (called delayed gastric emptying). Whilst this has the effect of helping you feel fuller for longer, it can also affect the way in which some medications are absorbed. In particular, concerns have been raised about the effects of weight loss injections on contraceptive pills and HRT.

A brief summary of the risks is outlined below:

Contraception:

If you are taking an oral contraceptive pill, GLP1 injections may make it less effective, meaning that there is a risk of pregnancy. This risk is thought to only apply to Mounjaro® (tirzepatide).

If you are using Mounjaro® (tirzepatide) and are taking oral contraception (combined pill or progesterone-only (mini) pill) it is recommended that you use an additional barrier method (e.g. condoms) for 4 weeks after starting Mounjaro® and for 4 weeks after every change of dose.

The College of Sexual and Reproductive Healthcare have put together this information to help advise patients on the most appropriate courses of action to take, when starting or changing the dose of a GLP1 injection:

Hormone Replacement Therapy:

The part of HRT we’re concerned about is oral progesterone (e.g. Utrogestan®, Geptrix®). Progesterone plays a vital role in protecting your womb lining (endometrium) if you’re taking oestrogen. If the progesterone isn’t properly absorbed, your womb lining could build up, putting you at risk of heavy bleeding, abnormal bleeding, or even endometrial cancer.

The British Menopause Society has issued guidelines specifically for women on Mounjaro®, Wegovy® and other GLP-1 medications. They recommend that you should ideally switch to a non-oral form of progesterone. Options include a Mirena® coil fitted in the womb (which we can do at the surgery), or a switch to a combined oestrogen and progesterone patch may be appropriate. You can find out more information about the Mirena coil here: https://www.mirena.co.uk/
If you stay on oral progesterone you should temporarily increase your progesterone dose, when starting Mounjaro® or Wegovy®, or when the dose of injection increases, typically for 4 weeks at a time.

If you feel that the above information applies to your current circumstance, or if you are using HRT alongside a GLP1 and have noticed a change in bleeding, unusual pelvic discomfort or changes in discharge, please contact us via a non-urgent healthcare request form to discuss this – never change your dose without first discussing it with a prescriber.