Oral vs transdermal hormone therapy: a Danish study maps the clot risk
Oral menopausal hormone therapy was linked to small absolute increases in clots, stroke and heart attack in Danish women, while patches and gels generally were not.
A nationwide study from Denmark, published in The BMJ on September 23, 2026, looked at whether today’s menopausal hormone therapy raises the risk of blood clots in veins, stroke and heart attack. It covered women aged 50 to 69 living in Denmark between 2003 and 2021 without prior clots, cancer or several other conditions.
Oral estrogen
Compared with no current use, oral estrogen, alone or with a progestin, was associated with higher rates of venous clots (hazard ratio 1.6), ischemic stroke (1.3) and heart attack (1.2). In absolute terms the extra risk per year was small: 0.09% for venous clots, 0.06% for stroke and 0.03% for heart attack, meaning about 1,055 women would need to use oral therapy for a year for one extra venous clot. Higher oral estradiol doses (above 1 mg a day) used for more than a year carried higher stroke and heart attack risks that grew with duration.
Patches and gels
Transdermal therapy, delivered through the skin, was not associated with higher clot, stroke or heart attack rates overall. The exception was transdermal combined cyclic therapy, which was linked to more heart attacks (hazard ratio 2.1).
This is an observational study, so it shows associations rather than proof of cause, though it matches earlier evidence that route matters.
What it means for you
If you are considering hormone therapy, the route and dose are worth discussing with your doctor, especially if you have other clot risk factors. Our HRT decision guide and hormone therapy article walk through the benefits and risks.