Injectable weight loss drugs, contraception and HRT

If you are considering using injectable weight loss medication, in combination with either contraception and / or oral progestogens for endometrial protection for HRT.

Recent guidance has been published in relation to the use of injectable weight loss medication safely as the use may impact contraception and have an impact on the effectiveness of  HRT to adequately protect your endometrium (womb lining). This increases your risk of cancer.

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

For those using injectable weight loss medication, please consider the following advice and make an appointment to discuss with your usual GP via the online consultation system to make changes.

Contraception:

• All women should use contraception when using injectable weight loss medication.

• Those taking Tirzepatide (Mounjaro) should switch to a non-oral method e.g. an implant or a coil, or add-in condoms for four weeks after initiation and four weeks after each dose increase, to prevent unwanted pregnancy.
• Those using oral contraception who experience vomiting or severe diarrhoea as a side-effect should follow the missed pills guidance in the pill packet.
• Please contact the practice if you want to discuss your contraception.

Hormone replacement therapy:

• Women with a BMI >30 should be using oestrogen via the skin e.g. patch, gel or spray. If you are not using oestrogen via this method, you are at increased risk of blood clots. Please contact the surgery to arrange an HRT review.

• Injectable weight loss injections delay gastric emptying and may therefore reduce absorption of oral progestogens. Transdermal or vaginal routes are unlikely to interact.

• Women should be advised to switch to a non-oral progestogen (combined patch or levonorgestrel intrauterine device (Mirena coil)) which would be preferable while the injectable weight loss medications are being used.
• If you do not wish to switch to a Mirena coil or a patch, please remain on your oral progestogen but arrange a consultation to increase the dose. Please be aware that there is uncertainty as to what the correct dose increase might be and whether increasing the dose is enough to ensure safety.

All these points should have been discussed with you by your private provider prior to commencing an injectable weight loss medication and at every dose change. Should you need further assistance, please contact the surgery.

Thank you Knowle House GP Partners.

June 2025