Estrogen Pill or Patch?What Studies Show About Blood Clot Risk

Blood clots in the leg veins or lungs, called venous thromboembolism (VTE), are one of the best-known risks of menopause hormone therapy. Research suggests the risk depends a lot on how estrogen enters your body.

Pills: a higher clot risk

A 2008 review of 17 studies found that estrogen pills raised the risk of a first clot, with about 2.5 times the odds of women not using estrogen.¹ The risk was highest in the first year and dropped back to normal after women stopped.¹ Being overweight or having an inherited clotting tendency raised the risk further for women taking pills.¹

A large 2019 U.K. study of more than 80,000 women with clots and nearly 400,000 without found:²

• Estrogen pills overall were linked to about 1.6 times the odds of a clot.
• The odds were higher with estrogen plus a progestogen (1.7) than estrogen alone (1.4).
• Estradiol pills carried less risk than conjugated equine estrogens.
• Conjugated equine estrogen with medroxyprogesterone had the highest risk, about twice the odds.

Patches and gels: no clear added risk

In both studies, estrogen through the skin, called transdermal estrogen, wasn’t linked to a higher clot risk.¹² The 2008 review found it didn’t seem to add risk even for women at higher risk of clots.¹

Clinicians writing in a 2024 prescribing journal said transdermal estrogen is preferred for women at risk of clots, and that the route of estrogen and the type of progestogen both matter.³ The 2019 authors noted that patches and gels seemed to be underused.²

Keep it in perspective

These are observational studies, which show links rather than proof.² Researchers say more data are needed on the many different regimens.¹ Your overall risk depends on your age, weight, history and other medicines.

Questions to ask

1. Do I have risk factors for clots, such as a past clot, family history, obesity or smoking?
2. Would a patch, gel or spray suit me better than a pill?
3. Which progestogen would I take, and does it matter for my risk?
4. What symptoms of a clot should make me call right away?

Our guides to whether hormone therapy is safe, estrogen gel precautions, a loose estrogen patch and sequential versus continuous combined therapy explain more.

Try: “My mother had a blood clot. If I start hormone therapy, should it be a patch or gel instead of a pill?”

My Body Changed. Now What? includes a Visit Brief. Use it to list your clot risk factors, family history and current medicines before you choose a form. See the book.