If you use menopausal hormone therapy, a headline saying that oral HRT “raises blood-clot risk” can feel personal—and alarming. But the new research behind that headline does not say every woman faces a high risk, that all forms of hormone therapy behave the same way, or that anyone should stop treatment on her own.
The new study indexed in PubMed examined women ages 50–69 in Denmark. It found different patterns for oral and transdermal hormone therapy. Oral estrogen, used alone or with a progestin, was associated with a higher rate of venous blood clots compared with no current use. Transdermal therapy—delivered through the skin—was not associated with higher thrombotic rates overall.
Those are important findings, but they are not the same as proof that pills caused clots or that patches have no risk. For anyone weighing HRT blood clot risk after 50, the study offers useful context, not a personal forecast. It was observational, not randomized, and its results describe groups rather than your individual medical history.
The short version
- Current oral estrogen therapy was associated with a 1.6-fold rate of venous thromboembolism, or VTE, compared with no current use.
- The reported absolute difference was 0.09 percentage points per year—about nine additional events per 10,000 users per year in this study population.
- Stroke and heart-attack associations were smaller overall and were concentrated in higher-dose oral estradiol used for longer periods.
- Transdermal therapy was not associated with increased thrombotic rates overall, but that does not mean every patch, gel, spray or regimen is risk-free.
- The research cannot prove cause and effect and may not transfer perfectly from Denmark to the United States or Canada.
- Do not stop, switch or change the dose of hormone therapy because of one study or one article. Talk with the clinician who prescribes it.
This article is educational and is not personal medical advice.
What the new HRT blood clot risk study examined
Published in The BMJ on September 23, 2026, the nationwide nested case-control study used Danish health registries from 2003 through 2021.
Researchers identified:
- 9,807 women with a first venous thromboembolism, including deep vein thrombosis or pulmonary embolism;
- 18,460 women with a first ischemic stroke; and
- 11,974 women with a first myocardial infarction, or heart attack.
Each case group was matched by birth year with women who had not experienced that outcome. That produced 49,035 matched controls for the clot analysis, 92,300 for stroke and 59,870 for heart attack.
Prescription records allowed the researchers to examine current hormone-therapy use by route, dose and duration. The comparison was current use versus no current use. This was not a trial that randomly assigned one group to pills and another to patches.
That design matters. Large health registries can detect patterns across many people, but they cannot remove every difference between people who use a treatment and those who do not.
Relative risk and absolute risk tell different parts of the story
The phrase “60% higher risk” comes from a hazard ratio of 1.6, but it does not tell you how often an event occurred in the first place. For that, you need the absolute numbers.
Here is what the study reported for oral estrogen therapy, alone or combined with progestin, compared with no current hormone-therapy use:
| Outcome | Rate among nonusers per 10,000 person-years | Oral-therapy hazard ratio | Reported absolute increase per year | Approximate one additional event per year |
|---|---|---|---|---|
| Venous thromboembolism | 15.8 | 1.6 | 0.09% | 1 in 1,055 users |
| Ischemic stroke | 20.3 | 1.3 | 0.06% | 1 in 1,642 users |
| Myocardial infarction | 13.0 | 1.2 | 0.03% | 1 in 3,846 users |
For blood clots, an absolute increase of 0.09 percentage points is about nine additional events per 10,000 oral-therapy users over one year. That is not zero. It is also very different from saying that 60% of users will develop a clot.
These numbers are averages from the study population. They cannot calculate your personal risk because individual risk depends on factors that a table cannot capture.
Did the dose and duration of oral HRT matter?
The pattern differed by outcome.
For venous blood clots, oral estradiol was consistently associated with higher risk across the dose and duration categories the researchers examined.
For ischemic stroke and heart attack, the increased associations were concentrated in women using oral estradiol at doses above 1 mg per day for more than one year. The abstract reports hazard ratios of 1.8 for both outcomes among women using that higher dose for more than five years, compared with no current use.
That dose threshold is not a personal prescribing rule. Products, combinations, symptoms, health histories and reasons for treatment differ. Ask whether your current route, dose and duration still make sense for you. Do not change them yourself because of a single study result.
What did the study find about estrogen patches and other transdermal therapy?
Transdermal therapy delivers medication through the skin, including patches, gels and sprays. In this study, transdermal therapy was not associated with increased rates of venous blood clots, ischemic stroke or heart attack overall compared with no current use.
One subgroup differed: combined cyclic transdermal therapy was associated with a higher heart-attack rate, with a hazard ratio of 2.1. The researchers cautioned that this estimate was based on sparse data, and its 95% confidence interval was wide—from 1.1 to 4.1.
The study observed different patterns by route, but it did not randomly assign treatments. Its overall transdermal finding is reassuring at a group level, not a guarantee for an individual. The small combined cyclic subgroup result also remains uncertain.
This route distinction is not entirely new. ACOG’s patient guidance, reviewed in 2024, says patches, sprays and rings may pose less blood-clot risk than pills taken by mouth. “May” is the important word.
What the study cannot tell you
The registry includes many women, but the design still has limits.
It cannot prove that oral therapy caused the events
People who use oral, transdermal or no hormone therapy may differ in ways that influence health outcomes. Statistical adjustment can reduce some of that imbalance, but it cannot guarantee that every relevant difference was measured.
The authors noted that the registry data did not include menopause age, body mass index or smoking. Each could affect how a clinician interprets an individual’s overall risk.
The population was Danish
Denmark’s healthcare system, prescribing patterns and population do not perfectly match those of the United States or Canada. The authors specifically cautioned that the findings may not apply in the same way to more ethnically diverse populations.
“No association found” is not “no risk exists”
A study can fail to detect an increased rate even when a small effect, a formulation-specific effect or a subgroup difference remains possible. The transdermal result should therefore be discussed as an observed group-level finding—not a guarantee.
Hormone therapy still has benefits as well as risks
Hormone therapy is prescribed because it can relieve symptoms and protect bone. Those benefits belong in the risk discussion.
The 2022 North American Menopause Society position statement says hormone therapy remains the most effective treatment for hot flashes and other vasomotor symptoms, as well as the genitourinary syndrome of menopause. It also helps prevent bone loss and fractures.
The statement emphasizes that the balance of benefits and risks varies with:
- the type and dose of therapy;
- how it is delivered;
- when treatment begins;
- how long it is used;
- whether a progestogen is included; and
- the individual’s health history and treatment goals.
For generally healthy women younger than 60 or within 10 years of menopause onset who do not have contraindications, the statement describes the benefit-risk balance as generally favorable for bothersome symptoms and bone-loss prevention. Starting after age 60 or more than 10 years after menopause calls for a more cautious assessment because absolute cardiovascular, clot and dementia risks are higher.
Those age and timing ranges are clinical context, not an automatic yes-or-no test.
If night sweats are part of the decision, our guide to menopause night sweats and disrupted sleep explains why symptom burden is worth discussing rather than dismissing.
What should you discuss with your clinician?
You do not need to arrive with a treatment decision. A clearer medication history and a few focused questions are more useful.
Bring or write down:
- the exact product name;
- whether it is a pill, patch, gel, spray or another form;
- the dose and schedule;
- when you started it;
- whether you still have a uterus and whether a progestogen is part of the regimen;
- the symptoms it is treating and how much they have improved;
- your personal history of blood clots, stroke, heart attack, cancer or liver disease; and
- relevant family history and other medicines.
Questions to ask include:
- What are the benefits of my current treatment for me now?
- How do my age, time since menopause and health history affect the risk discussion?
- Is the current route and dose still appropriate for my goals?
- Would another route change the likely benefits or risks in my situation?
- How often should we review whether to continue?
- What symptoms should prompt urgent care?
ACOG recommends revisiting the decision annually based on symptoms, benefits and risks. Some women continue longer because symptoms persist; the point is periodic review, not an arbitrary stop date.
If you take several prescriptions, the medication review after 65 checklist can help you organize names, doses and questions before an appointment.
When blood-clot symptoms need medical attention
Venous thromboembolism includes deep vein thrombosis (DVT) and pulmonary embolism (PE). DVT most often forms in the deep veins of a leg. PE can occur when part of a clot travels to the lungs.
According to the CDC, common DVT signs in the affected arm or leg include:
- swelling;
- pain or tenderness;
- warmth; and
- redness or discoloration.
Contact a clinician as soon as possible if these symptoms occur.
Signs of a possible pulmonary embolism can include difficulty breathing, a faster or irregular heartbeat, chest pain that worsens with a deep breath or cough, coughing up blood, severe lightheadedness or fainting. Seek emergency medical help immediately for possible PE symptoms.
These signs can have other causes, but an article cannot safely sort them out for you.
The bottom line
The new BMJ study adds useful evidence to the HRT blood clot risk conversation because it does not treat every formulation as one exposure.
Among Danish women ages 50–69, current oral estrogen therapy was associated with a higher venous-clot rate compared with no current use. The absolute increase was 0.09 percentage points per year in this study. Transdermal therapy was not associated with increased thrombotic rates overall, although one combined cyclic subgroup finding was uncertain.
Use the result to make your next conversation with a clinician more specific. It does not justify panic or a treatment change on your own. Route, dose, timing, symptoms and personal history all belong in the decision.
Frequently asked questions
Does oral HRT cause blood clots?
The new study found an association between current oral estrogen therapy and a higher venous-clot rate compared with no current use. Because the study was observational, it cannot prove that oral therapy caused every event.
Is an estrogen patch safer than a pill?
The study did not find higher thrombotic rates for transdermal therapy overall, and ACOG says patches, sprays and rings may pose less clot risk than oral pills. That does not mean every patch or regimen is risk-free. The study was not a randomized pill-versus-patch trial, so the choice still requires individual clinical review.
How large was the absolute blood-clot difference?
The reported annual increase was 0.09 percentage points—about nine additional VTE events per 10,000 oral-therapy users per year, or one additional event per approximately 1,055 users for one year in this study population.
Should I stop taking oral HRT?
Do not stop, switch or change the dose on the basis of an article or one study. Contact the clinician who prescribes it and review your symptoms, medical history, product, route, dose and treatment goals.
Who was included in the study?
It used Danish national health-registry data for women ages 50–69 between 2003 and 2021. The results may not transfer perfectly to other countries or more ethnically diverse populations.
What symptoms could signal a blood clot?
DVT signs can include swelling, pain or tenderness, warmth, and redness or discoloration in an arm or leg. Possible PE signs include difficulty breathing, chest pain that worsens with a breath or cough, coughing up blood, an unusually fast or irregular heartbeat, severe lightheadedness or fainting. Seek medical help immediately for possible PE symptoms.
Sources
- Contemporary menopausal hormone therapy and thrombotic disease: nationwide nested case-control study — PubMed
- BMJ Group summary of the study and its limitations — News-Medical
- Hormone Therapy for Menopause — American College of Obstetricians and Gynecologists
- The 2022 hormone therapy position statement — PubMed
- About Venous Thromboembolism — CDC
Accuracy note: This article distinguishes observational associations from causation and preserves the study’s Danish population, age range, time period and missing-variable limitations. Medical guidance was checked against ACOG, the North American Menopause Society position statement and CDC safety information on September 27, 2026.