The short answer
Menopausal hormone therapy eases menopause symptoms but affects cancer risk. Combined estrogen-plus-progestin raises breast cancer risk; estrogen alone affects risks differently. Decisions balance symptom relief against risks with your doctor.
Menopausal hormone therapy is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by taking prescription hormone therapy for menopause symptoms.
It is most strongly linked to breast cancer (with combined therapy) and endometrial cancer (with estrogen alone).
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
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The simple version
This page is for anyone thinking about hormone therapy for menopause, or supporting someone who is. It explains how it affects cancer risk.
Menopausal hormone therapy (MHT) uses estrogen, sometimes with progestin, to ease menopause symptoms such as hot flashes. It can raise the risk of some cancers, and it affects others differently. This is a personal decision to make with your doctor, weighing benefits against risks.
What menopausal hormone therapy is
MHT replaces hormones that decline at menopause. "Combined" therapy uses estrogen plus progestin, and it is for people who still have a uterus. "Estrogen-only" therapy is used after a hysterectomy. Large trials shaped what we know about the risks and benefits. The Women's Health Initiative was one of them.
How people are exposed
Common ways people come into contact with it:
- Taking prescription estrogen, with or without progestin, for menopause symptoms.
- Pills, patches, gels, or other forms.
- Use is guided by a doctor, based on symptoms and health history.
The cancer connection
Combined estrogen-plus-progestin therapy raises breast cancer risk. Estrogen-alone therapy raises the risk of endometrial cancer if the uterus is still present. That is why progestin is added. Estrogen alone affects other cancers differently. Some risks fall after a person stops.
IARC places menopausal hormone therapy in Group 1, carcinogenic to humans. Group 1 is its strongest evidence category. It means there is enough evidence that MHT can cause cancer in people. IARC is the World Health Organization's cancer research agency. In the United States, the National Toxicology Program lists steroidal estrogens in its Report on Carcinogens as known to be human carcinogens. Menopausal hormone therapy itself is not listed under that name.
Hazard is not the same as risk
Hazard and risk are easy to mix up. Listing MHT as a carcinogen is a statement about hazard. Hazard is whether something can cause cancer under some conditions. On its own it says nothing about your personal risk. That depends on how much you take, for how long, and other factors. Things placed in the same group can still differ a lot in real-world risk. The label answers one question: can it cause cancer? It does not answer how likely that is for you.
Questions to raise with your doctor
MHT is a prescribed treatment, so choices about it are made with your doctor. Steps that help:
- Talk through your personal risks and benefits.
- Ask about using the lowest effective dose for the shortest time that meets your needs.
- Keep up with recommended breast screening and other screening.
- Report any unusual bleeding promptly.
To see where menopausal hormone therapy sits among all the things that affect cancer risk, read our overview of cancer prevention and what raises cancer risk.
The bottom line
Menopausal hormone therapy is a known human carcinogen (IARC Group 1). It can also ease hard symptoms. The label alone does not decide whether it is right for you. Weigh the benefits and risks with your doctor, and keep up with screening.
Common questions
Does menopausal hormone therapy cause cancer?
Yes. Menopausal hormone therapy is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to menopausal hormone therapy?
Most exposure happens by taking prescription hormone therapy for menopause symptoms. This is a prescribed medical treatment, so decisions are made individually with a clinician.
Which cancers are linked to menopausal hormone therapy?
It is most strongly linked to breast cancer (with combined therapy) and endometrial cancer (with estrogen alone).
How can I reduce my exposure to menopausal hormone therapy?
The main steps are individualized decisions with your doctor and regular screening.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether menopausal hormone therapy can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
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Last updated: 2026-08-10Next planned review: 2028-07-05
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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