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Medication interactions
Medication interactions between weight loss injections with contraception and HRT
GLP-1 injections (Mounjaro or Wegovy) are used to treat diabetes and obesity. We are aware patients are able to pay for these to be prescribed by private clinics who may not be able to see you regular medications
Weight Loss Injections and contraception
It is recommended that all women under the age of 55 who are taking GLP-1s such as Tirzepatide (Mounjaro) should use a contraception that is not an oral tablet for 4 weeks after starting and 4 weeks after each dose increase. This could be condoms/femidoms or a longer acting contraceptive such as the injection, coil or implant. You can read more about these options or book in with a Practice Nurse or GP to discuss them with us.
Please also note that vomiting and diarrhoea can occur with GLP1-s. This may affect how well tablet contraception absorbs. Please read the leaflet in the pill packet to see what you need to do to keep your contraceptive cover if you have vomiting or diarrhoea.
If you need emergency contraception whilst on a GLP-1 the recommended option is a copper coil. This is because there isn't much data to know how the Emergency Contraceptive pills absorb in someone taking a GLP-1.
Weight Loss injections and HRT
HRT usually has 2 separate hormones - oestrogen and progesterone. Your risks of blood clot are increased with obesity and tablet oestrogen. Therefore women on Mounjaro or Wegovy for obesity are advised to take a transdermal (patch, gel or spray) type of oestrogen.
In women who have not had a hysterectomy (an operation to remove their womb) a progesterone will be prescribed as well as the oestrogen for their HRT. The progesterone protects your womb lining from thickening to reduce the risk of endometrial cancer.
There haven't been enough studies to know how GLP-1s affect the progesterone absorption. Theoretically progesterone that is given as a patch or Vaginally (vaginal tablet/pessary) is more likely to absorb properly. The recommendation is therefore to switch tablet progesterone to a patch or a Mirena Coil (a coil that emits progsterone that sits in the womb).
If you have concerns about how your weight loss injection might interact with your HRT please book a GP appointment to discuss your HRT. If you are receiving your GLP-1 from a private provider please contact them to discuss any concerns.
Published: Jun 2, 2026