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Quick answer
Mounjaro delays stomach emptying. There is concern that this could reduce absorption of oral progestogens or progesterone used in combined HRT, particularly after starting treatment and following dose increases.
The evidence is limited, so do not stop HRT or change the progesterone dose yourself. Ask for an HRT review when starting Mounjaro.
Why does progesterone matter?
If you have a uterus and use oestrogen, adequate progesterone protects the lining of the womb. Reduced absorption could theoretically reduce that protection. This is why the oral progesterone component deserves specific attention rather than simply checking whether your oestrogen symptoms remain controlled.
Which HRT types are less likely to be affected?
No routine change
The British Menopause Society advises that a combined transdermal patch is not expected to be affected.
No routine change
A 52 mg levonorgestrel intrauterine system provides local endometrial protection and is not affected by delayed stomach emptying.
Absorption unaffected
Oestrogen delivered through a patch, gel or spray does not rely on absorption through the stomach.
Arrange a review
Oral oestrogen may be switched to a transdermal option, and oral progesterone may need an alternative route or clinician-led dose adjustment.
What might the clinician discuss?
Depending on your HRT, preferences and medical history, the clinician may discuss switching to a combined patch, using a 52 mg levonorgestrel coil for womb-lining protection, or temporarily adjusting oral progesterone around Mounjaro initiation and dose increases.
British Menopause Society suggestions about oral progesterone are pragmatic expert guidance because direct research evidence is not yet available. Your plan should therefore be individual.
Report unexpected bleeding
Tell your GP about new or unexpected vaginal bleeding while using HRT, including bleeding that begins after starting Mounjaro or increasing the dose. Most bleeding is not caused by cancer, but it should be assessed according to current HRT bleeding guidance.
The key message
HRT and Mounjaro can be used together, but oral progesterone needs thought. Arrange a review; do not stop oestrogen or alter progesterone without clinical advice.
Specialist guidance
British Menopause Society: Incretin-based therapies in women using HRT
First published July 2026. Last reviewed: 16 July 2026. Planned review: October 2026, or earlier if British Menopause Society guidance changes.
Prepared for the Pathfields Healthy Living Portal.