Blood Thinners, the Pill and HRT: The New Findings

Hormone replacement therapy, birth control pills may be safe for women on blood thinners

/ Author:  / Reviewed by: Jennifer Gershman, PharmD, CPh

(RxWiki News) Women with a history of blood clots are often advised to stop hormone replacement therapy (HRT) or using birth control pills — even if they are already on a blood thinner. But a new discovery could change that.

A new study from Italy found that women on blood thinners can safely be put on HRT or hormone-containing birth control without an increased risk of blood clots or abnormal uterine bleeding.

"While it has been common practice among health-care providers to avoid prescribing hormone therapy and anticoagulants at the same time, there has been no evidence to support this decision," said lead study author Ida Martinelli, MD, of the A. Bianchi Bonomi Hemophilia and Thrombosis Center in Italy, in a press release.

For this study, Dr. Martinelli and team looked at the rates of recurrent blood clots and abnormal uterine bleeding in 1,888 women on blood thinners both with and without hormone-containing drugs.

Women on blood thinners with hormone therapy experienced recurrent blood clots at a rate of 3.7 percent per year. In contrast, those not on hormone therapy experienced them at a rate of 4.7 percent per year.

The rate of abnormal uterine bleeding in women on hormonal therapy was 22.5 percent, compared to 21.4 percent for those not on hormone therapy.

According to Dr. Martinelli and team, the similarities in these rates suggests that the combined use of blood thinners and hormone therapy is safe.

"For the first time, we demonstrate that women suffering from blood clots can safely take hormone-containing contraceptives or hormone replacement therapy with anticoagulants, providing women the freedom to choose the method of birth control and other hormone-containing medications they prefer," Dr. Martinelli said. "While further investigation is needed ... these results dispel former misconceptions and should allow clinicians to confidently treat their patients who take blood thinners and hormones concurrently."

This study was published online Dec. 22 in the journal Blood.

No funding sources or conflicts of interest were disclosed.

Review Date: 
December 21, 2015
Last Updated:
December 23, 2015