HRT is not automatically ruled out for trans people with heart conditions or atrial fibrillation. Cardiovascular risk needs careful, individualised assessment before and during hormone therapy. The route of administration, the type of hormone, and the dose all affect risk, and most people with cardiac history can access affirming care safely with the right monitoring.
Why the question is harder than a yes or no
People tell me this is one of the most anxiety-inducing conversations they face. They have waited, sometimes for years, to reach a point where hormone therapy feels possible, and then a pre-existing heart condition lands in the middle of it and they are told to wait again, or simply turned away. That is not always the right clinical call, and it is almost never a complete answer.
Cardiovascular risk in hormone therapy is real, worth taking seriously, and entirely possible to navigate. The job is not to pretend the risk does not exist. The job is to assess it accurately, weigh it against the very real harm of withholding affirming care, and find the approach that serves the actual person in front of you.
What cardiovascular risk actually means in this context
The term covers several different things, and conflating them leads to both over-caution and under-caution.
Blood clotting risk, or venous thromboembolism (VTE), is the one most often raised in the context of oestrogen therapy. Oestrogen increases the production of certain clotting factors in the liver, raising the risk of deep vein thrombosis (DVT) and pulmonary embolism. This is a real effect, but it is not uniform across all forms of oestrogen, and it is significantly modified by how the hormone is delivered.
Atrial fibrillation (AF) is a separate concern. AF is an irregular heart rhythm that itself raises stroke risk, partly because blood can pool in the heart and form clots. Someone managing AF with anticoagulants is already on medication that affects clotting. Adding oestrogen into that picture requires careful thought, but careful thought is not the same as an automatic veto.
There are also arterial risks to consider: high blood pressure, coronary artery disease, and the effect of hormones on cholesterol and lipid profiles. Testosterone, for example, tends to raise haematocrit (the proportion of red blood cells in the blood) and can affect blood pressure and lipid levels, all of which matter for someone with pre-existing cardiovascular disease.
Route of administration: why it changes the calculation
This is the piece that makes the biggest practical difference, and it is the one most often left out of the conversation when someone is turned away at the first hurdle.
Oral oestrogen passes through the liver before it enters the bloodstream, and this first-pass metabolism is where most of the clotting-factor effect happens. Transdermal oestrogen, delivered through a patch or a gel applied to the skin, bypasses the liver. The evidence base consistently shows that transdermal oestrogen carries substantially lower VTE risk than oral oestrogen. For someone with a cardiac history, this distinction matters enormously.
Injected oestrogen has its own profile: it is not subject to first-pass metabolism in the same way, but it produces peak-and-trough hormone levels rather than the more stable pattern of a patch or gel, which brings its own considerations.
For trans women or non-binary people assigned male at birth who are on anti-androgens as well as oestrogen, the anti-androgen choice also matters. Cyproterone acetate, spironolactone, and bicalutamide each carry different cardiovascular profiles. A good prescriber looks at the whole picture, not just the oestrogen in isolation.
For trans men and non-binary people assigned female at birth using testosterone, the main cardiovascular concerns are haematocrit, blood pressure, and lipid levels, all of which are monitorable through routine blood tests. Raised haematocrit increases blood viscosity, which matters particularly for someone with a clotting or cardiac history. The answer is monitoring and, if needed, dose adjustment, not refusal.
What individualised assessment looks like
The phrase "individualised assessment" appears in every set of clinical guidelines, including the WPATH Standards of Care and the Endocrine Society guidelines, and it means something specific. It does not mean "we will check your bloods once and decide". It means a clinician looks at:
- the nature and severity of the cardiac condition
- current treatment and how well the condition is managed
- other cardiovascular risk factors: smoking, weight, blood pressure, family history, diabetes
- the person's age and general health picture
- the form, dose, and route of the hormone being considered
- whether additional monitoring or specialist involvement is warranted
For most people with atrial fibrillation or other managed cardiac conditions, this assessment does not end in a permanent no. It ends in a specific plan: this form of hormone at this dose, monitored in this way, reviewed at these intervals, with a cardiologist in the loop if needed.
The involvement of a cardiologist is not a barrier to care. It is a collaboration. A good gender-affirming prescriber knows when to ask for that input and how to frame the question. What does not serve the patient is a cardiologist or GP who is not familiar with gender-affirming care giving a blanket refusal based on a general sense of risk, rather than an actual assessment of this person's profile.
Atrial fibrillation specifically
AF raises a few particular questions that are worth addressing directly.
If someone with AF is already anticoagulated, which many people with persistent AF are, then the baseline clotting risk is already being managed pharmacologically. Adding transdermal oestrogen does not straightforwardly compound that risk in the way oral oestrogen might. It changes the picture, but it does not automatically worsen it, and a prescriber familiar with both sides of this can make that call.
AF is also associated with thyroid conditions, and thyroid function is something gender-affirming hormone therapy can affect in some people. This is not a reason to avoid treatment; it is a reason to include thyroid function in routine monitoring.
Rate-controlled or rhythm-controlled AF in someone who is otherwise well and whose anticoagulation is stable is a very different risk profile from uncontrolled, poorly managed AF in someone with multiple other comorbidities. Treating those as the same situation is a clinical error, not caution.
The harm of withholding care
This part of the conversation is often missing, and it should not be. The framing of "is HRT safe given this cardiac condition" implicitly treats the alternative as neutral. It is not. Withholding affirming care carries its own significant risks: worsening dysphoria, mental health deterioration, the ongoing physical effects of an unwanted hormonal environment, and the documented harm to wellbeing that follows from being denied care that you know you need.
Risk assessment in medicine is not a one-sided exercise. The question is not "does HRT carry any risk". The question is "what are the risks of treating, against the risks of not treating, for this person, now". That calculation often comes out in favour of carefully monitored hormone therapy, even for people with cardiac history.
What to do if you have been turned away
A refusal from one clinician is not the end. If you have been told your heart condition rules out HRT, it is worth asking for the specific clinical reasoning, because "it increases risk" is not a complete answer. Risk of what, by how much, compared to what alternative, and has the prescriber considered transdermal routes?
A second opinion from a clinician with specific expertise in gender-affirming care is entirely reasonable. GenderGP's doctors are specialists in this area and can assess your specific cardiac history, discuss routes and doses, and work alongside your existing cardiac care team where needed. If you are ready to explore the medical pathway, GenderGP is the place to start that conversation.
If your cardiologist has concerns, ask them to be specific. A question framed as "what would you need to see in order to feel comfortable with transdermal oestrogen at a low dose alongside your existing anticoagulation" is a more productive conversation than accepting a general no.
Monitoring throughout treatment
For anyone with cardiac history on hormone therapy, monitoring is not optional. Blood pressure, blood tests including lipid profiles, haematocrit for those on testosterone, and regular review of the cardiac condition itself are all part of the picture. The frequency and scope of monitoring will depend on the individual's profile, and a good prescriber sets that out clearly from the start.
The goal is not to monitor so heavily that the experience of being on hormones feels like permanent surveillance. The goal is to catch anything that needs adjusting early, before it becomes a problem. Most people with cardiac histories who are on affirming hormone therapy lead entirely ordinary lives, take their hormones as they would any other medication, and have the same kind of routine check-ups they had before.
If there is a topic that you would like me to cover, just let Sammy know.
Dr Helen Webberley is a gender specialist, medical educator, and advocate, and the founder of GenderGP. She writes about gender diversity, trans healthcare, and the lives of trans and gender-diverse people.
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