Does HRT increase breast cancer risk?
Reviewed by Kindr Health Clinical Team · Last reviewed July 3, 2026
Answer published
The Women's Health Initiative — the trial people quote — actually showed estrogen-alone HRT (for women without a uterus) slightly reduced breast cancer incidence and mortality. Combined estrogen-plus-progestin showed a small absolute increase after ~5 years of use: roughly 1 additional case per 1,000 women per year. For perspective, this is smaller than the risk added by 1 drink of alcohol per day or by being obese. Newer combined regimens using micronized progesterone (not the synthetic progestins used in WHI) appear to have an even smaller signal. The conversation should always be about your personal baseline risk, not population averages.
Related on Kindr Health
People also ask
- Is hormone replacement therapy (HRT) safe? →
For healthy women under 60 or within 10 years of menopause, modern HRT is considered safe and effective by NAMS, the Endocrine Society, and ACOG.
- What is the difference between bioidentical and synthetic hormones? →
"Bioidentical" hormones are structurally identical to your body's. FDA-approved bioidentical estradiol/progesterone differ from compounded cBHRT.