Scientists confirm menstrual cycles can affect how well drugs work

Scientists are only now confirming that women’s menstrual cycles can affect how drugs perform in the body, according to the New York Post.

New research points to fluctuating estrogen levels influencing drug metabolism, following studies on COVID-19 vaccines showing women vaccinated during the follicular phase had 35% more side effects but longer protection than those vaccinated during the luteal phase.

Separately, a once-failed Alzheimer’s-related drug, davenutide, was found effective in women but not men. A 2025 review also showed estrogen affects CYP liver enzymes responsible for metabolizing 50-80% of common drugs, including ibuprofen and caffeine.