Does hypothyroidism affect heart rate?
This article is written by mr.hotsia, a curious traveler who has spent years exploring Thailand, Laos, Vietnam, Cambodia, Myanmar, India and many other Asian countries.
On crowded buses and in small clinics above markets, I often hear the same surprised line:
“I thought hypothyroidism only makes you tired and gain weight,
but my doctor says it also affects my heart rate.”
Some people notice that their pulse is slower than before.
Others feel a heavy, slow heartbeat and strange tiredness when walking up stairs.
So the big question is:
Does hypothyroidism really affect heart rate, or is that just a coincidence
In this article I will not diagnose or treat anyone. Instead, we will walk through in simple language how low thyroid function can influence the heart and heart rate, what symptoms people notice, how treatment may change things, and when to talk to a doctor.
Short answer: yes, hypothyroidism can slow heart rate
Thyroid hormones act like a general energy signal for the body.
When thyroid levels are normal:
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The heart beats at a comfortable speed
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Blood vessels adjust smoothly
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The body can respond to exercise and emotions with proper changes in heart rate
When thyroid function is low:
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The heart receives less of this energy signal
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The pulse often becomes slower than usual for that person
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The heart may pump less forcefully
So yes, hypothyroidism can affect heart rate, most commonly by slowing it down. This slower heart rate is called bradycardia when it is lower than expected.
Not everyone with hypothyroidism has a very slow pulse, but the connection is strong enough that many doctors check thyroid when they see unexplained bradycardia.
How thyroid hormones and the heart work together
On the road from Chiang Rai to Kolkata, I see that the heart is like the central station of the body, and thyroid hormones are part of the scheduling office.
Thyroid hormones help:
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Set the basic heart rate
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Influence how strongly the heart muscle contracts
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Help control blood vessel tone
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Support how the heart responds to exercise and stress
If thyroid hormones are low:
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The heart relaxes its pace
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The pumping power can quietly decrease
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The circulation may slow slightly
This does not mean the heart stops working. It means it works in a slower, lower energy mode, which is fine for some people and problematic for others, depending on how low and for how long.
What does a low thyroid heart rate feel like?
Many people with hypothyroidism describe feelings like:
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“My heart beats slowly but heavily.”
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“I get tired faster when walking uphill.”
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“I feel cold and sluggish, including my heartbeat.”
Typical patterns can include:
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Resting heart rate lower than usual
For example, someone who used to have 75 beats per minute at rest might now have 55 to 60, without being an athlete. -
Reduced exercise tolerance
Walking, climbing stairs or carrying bags may feel harder, with more fatigue than expected. -
Cold hands and feet
Circulation can feel slower, adding to the feeling of low energy.
Sometimes the slow heart rate causes no symptoms at all. In other people it can lead to:
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Dizziness
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Lightheadedness
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Feeling close to fainting
These more serious symptoms need medical attention.
Hypothyroidism vs hyperthyroidism in the heart
On my travels, I hear people mix up low and high thyroid effects.
A simple way to remember:
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Hyperthyroidism (overactive thyroid)
Heart tends to be fast, jumpy, sometimes with palpitations and irregular rhythms. -
Hypothyroidism (underactive thyroid)
Heart tends to be slow, heavy, with reduced pumping strength in stronger cases.
Think of hyperthyroidism as the heart being pushed to hurry too much, and hypothyroidism as the heart being told to work in slow motion.
Both extremes can cause problems. The goal of treatment is to support a calm, steady middle.
Other heart related effects of hypothyroidism
Heart rate is only one part of the story. Low thyroid function can influence several other heart and circulation features.
1. Blood pressure
Hypothyroidism can be associated with:
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Normal or slightly raised blood pressure
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Sometimes higher diastolic blood pressure, which is the lower number
The pattern is not the same in every person, but the heart and blood vessels feel the slower metabolism.
2. Pumping strength and fatigue
In stronger or long term cases, low thyroid can reduce how forcefully the heart pumps. This may lead to:
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Shortness of breath on exertion
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Easy fatigue
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Swollen ankles in some people
Doctors sometimes discover reduced heart function in people whose main issue is unrecognized hypothyroidism.
3. Cholesterol and arteries
As we discussed in another article, hypothyroidism can raise LDL cholesterol in some people. Over years, this may influence artery health and overall heart risk if not addressed.
So the thyroid does not only affect the heartbeat, it also quietly shapes the environment in which the heart works.
Does treating hypothyroidism normalize heart rate?
This is one of the hopeful parts of the journey.
When hypothyroidism is treated with the right dose of thyroid hormone:
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The heart rate often returns closer to that person’s natural baseline
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Exercise tolerance can improve
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Some people feel less heavy and more energetic
However, a few important points:
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Improvement usually takes weeks to months, not just a few days
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If heart rate has been very slow for a long time, recovery can be gradual
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In older adults or people with heart disease, doctors often increase thyroid dose carefully to avoid stressing the heart
If there are other heart conditions or risk factors, such as coronary artery disease or long term high blood pressure, some heart problems may remain even after thyroid is corrected.
Thyroid treatment can support better heart function, but it is not a magic eraser for all cardiac history.
Can a slow heart rate be from athletic fitness, not thyroid?
Yes. This is a common confusion.
Some people, especially those who:
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Exercise regularly at a high level
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Are runners, cyclists or other endurance athletes
have naturally low resting heart rates, sometimes 50 or even below. They usually:
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Feel well
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Have good exercise tolerance
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Do not have typical hypothyroid symptoms
In these people, a slow heart rate can be a sign of efficient heart conditioning, not disease.
In hypothyroidism, the slow heart rate is more often:
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Accompanied by fatigue, cold intolerance, constipation or weight gain
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Combined with low energy and reduced stamina
Only a doctor, with thyroid tests and a full history, can separate athletic bradycardia from low thyroid bradycardia.
When is a slow heart rate a concern with hypothyroidism?
Across Thailand, Laos, Vietnam, Cambodia, Myanmar and India, I meet many people who check their own pulse with new smartwatches and then worry.
A slower heart rate may be concerning if:
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You feel dizzy or lightheaded
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You have episodes of almost fainting or actual fainting
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You are very short of breath with mild activity
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You have chest discomfort or pressure
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You have known heart disease and new worsening symptoms
These signs mean you should speak to a doctor promptly. Do not assume “it is just thyroid” or adjust medicine on your own.
How doctors look at heart rate in hypothyroidism
When a doctor evaluates someone with low thyroid and heart concerns, they often:
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Check thyroid function by blood tests
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TSH, Free T4 and sometimes other markers
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Assess how underactive the thyroid is
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Take a detailed history
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Symptoms like fatigue, dizziness, chest pain, breathlessness
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Exercise level and lifestyle
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Measure vital signs and examine the heart
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Blood pressure
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Pulse rate and rhythm
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Listen with a stethoscope
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Order tests if needed
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Electrocardiogram (ECG) to see the heart’s electrical pattern
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Echocardiogram in some cases to see heart structure and pumping
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Cholesterol and other blood tests
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Start or adjust thyroid treatment carefully
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Especially in older patients or people with heart disease, dose changes are usually gradual
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Their goal is to support the heart, not shock it with sudden hormone shifts.
Lifestyle steps that may support heart health with hypothyroidism
Lifestyle changes cannot replace medical care, but they can support your heart while thyroid treatment is being adjusted.
Here are gentle steps that may help:
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Move regularly within your limits
Short walks, simple stretching or low impact activity can help circulation and mood. Avoid sudden, very intense efforts if you feel unwell or dizzy. -
Eat in a heart friendly style
More vegetables, fruits, whole grains, beans, nuts and balanced fats may support heart and blood vessel health. -
Avoid smoking
Smoking is a strong stress on the heart and arteries, especially when other conditions like hypothyroidism and high cholesterol are present. -
Be careful with stimulants
Too much caffeine or other stimulants can cause uncomfortable heart sensations, especially while thyroid dose is being adjusted. -
Take medications as prescribed
Regular use of thyroid and any heart medications, plus follow up tests, helps keep the system more stable.
These steps are not a cure, but they are a kind way to support the bridge between your thyroid and your heart.
Final thoughts from the road
From small village clinics in Laos to big cardiology centers in India, I see the same pattern.
The thyroid is small and quiet, but it speaks loudly to the heart.
The balanced truth is:
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Yes, hypothyroidism can affect heart rate, most often by slowing it and reducing overall heart energy.
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Treating low thyroid can often help the heart beat at a more natural pace and improve stamina.
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Other heart risks such as age, blood pressure, smoking, weight and cholesterol still matter and need their own care.
Your heart and your thyroid are teammates. Keeping both in mind, and working with a doctor when something feels wrong, is one of the best gifts you can give your future self.
10 Frequently Asked Questions about hypothyroidism and heart rate
1. Does hypothyroidism usually make the heart rate slow or fast
It usually makes the heart rate slower than normal for that person. Hyperthyroidism tends to make the heart rate faster, while hypothyroidism tends to slow it.
2. What heart rate is considered too slow with hypothyroidism
There is no single number for everyone. Some people are comfortable at 55 beats per minute, especially if fit. Concern is higher when the rate is low and there are symptoms such as dizziness, fainting or breathlessness. A doctor should decide in each case.
3. Can a slow heart rate from hypothyroidism be dangerous
It can be, especially if the slowing is marked and associated with symptoms or if there is pre existing heart disease. In some cases it is mild and causes little trouble, in others it needs urgent attention. This is why medical evaluation is important.
4. Will my heart rate go back to normal when my thyroid is treated
In many people, heart rate moves closer to their usual baseline once thyroid levels are corrected. The speed and degree of improvement depend on age, other heart conditions and how long the thyroid has been low.
5. How long does it take for heart rate to improve after starting thyroid medication
Thyroid replacement typically takes several weeks to adjust levels and for the body to respond. Some people notice changes within a few weeks, others more gradually over months.
6. Can a normal heart rate mean my thyroid is fine
Not necessarily. Some people with hypothyroidism have normal resting heart rates. Thyroid status must be judged by blood tests, symptoms and examination together, not heart rate alone.
7. Is it safe to exercise if I have hypothyroidism and a slower heart rate
Gentle, appropriate exercise is often encouraged, but intensity and type should match your condition. If you have chest pain, severe breathlessness or dizziness, you should stop and seek medical advice.
8. Can thyroid medication make my heart beat too fast
If the dose is too high, thyroid replacement can make the heart rate faster and cause symptoms like palpitations. This is why regular testing and dose adjustments with a doctor are important.
9. Should everyone with an abnormal heart rate be tested for thyroid problems
Not everyone, but thyroid testing is often part of the evaluation for unexplained slow or fast heart rates, especially if there are other thyroid related symptoms.
10. What is the best first step if I think my heart rate issues are related to hypothyroidism
The best step is to note your symptoms, measure your pulse when calm if you can, and see a doctor. Ask for a thyroid evaluation if you have not had one, or a review of your treatment if you already have hypothyroidism. The doctor can then decide how to protect both your thyroid balance and your heart.
I’m Mr.Hotsia, sharing 30 years of travel experiences with readers worldwide. This review is based on my personal journey and what I’ve learned along the way. Learn more |