Thyroid Problems and Heart Palpitations: Can Your Thyroid Make Your Heart Race?
An overactive thyroid can make the heart beat faster, harder or irregularly. For some patients, heart palpitations are one of the symptoms that leads to thyroid testing.
Hyperthyroidism is an important and treatable cause of palpitations. However, not every palpitation in someone with thyroid disease is caused by the thyroid, so the heart rhythm and other possible causes still need to be considered when appropriate.
Can Thyroid Problems Cause Heart Palpitations?
- Yes. Hyperthyroidism — too much thyroid hormone — can cause a rapid, forceful or irregular heartbeat.
- Other symptoms may include tremor, heat intolerance, sweating, anxiety, weight loss and difficulty sleeping.
- Hyperthyroidism increases the risk of certain arrhythmias, particularly atrial fibrillation.
- Common causes include Graves’ disease and overactive thyroid nodules. Thyroiditis and some medicines can also produce excess circulating thyroid hormone.
- Testing usually begins with TSH. If TSH is low, free T4 and free T3 are generally measured.
- Beta-blockers may reduce rapid heartbeat and tremor, but they do not usually correct the underlying thyroid hormone excess.
- Treatment of the thyroid disorder depends on its cause and may involve antithyroid medication, radioactive iodine or thyroid surgery.
How Does the Thyroid Affect the Heart?
The thyroid is a small gland located at the front of the neck. It produces thyroid hormones, mainly thyroxine (T4) and triiodothyronine (T3).
These hormones influence metabolism throughout the body and have important effects on the cardiovascular system.
When thyroid hormone levels are excessive, the heart may:
- Beat faster
- Contract more forcefully
- Pump more blood per minute
- Become more susceptible to some arrhythmias
These changes can be perceived as racing, pounding, fluttering or irregular heart palpitations.
What Is Hyperthyroidism?
Hyperthyroidism means that the thyroid gland is producing too much thyroid hormone.
You may also hear the term thyrotoxicosis. Thyrotoxicosis is the broader term for having too much thyroid hormone circulating in the body, regardless of how it got there.
This distinction matters because some conditions, such as thyroiditis, can release stored thyroid hormone without the gland actually producing excessive new hormone.
What Other Symptoms Suggest Hyperthyroidism?
Racing or Irregular Heartbeat
A fast, forceful or irregular heartbeat is a common cardiovascular manifestation of hyperthyroidism.
Tremor
Fine shaking of the hands can occur with excessive thyroid hormone activity.
Heat Intolerance
You may feel unusually warm or sweat more than expected.
Weight Loss
Weight loss may occur even when appetite remains normal or increases.
Anxiety & Irritability
Nervousness, restlessness, irritability and difficulty sleeping may occur.
Neck or Eye Changes
Some patients develop an enlarged thyroid gland. Graves’ disease may also cause characteristic eye problems.
If you are uncertain whether the sensation you feel is truly a palpitation, see our heart palpitation symptoms cornerstone guide.
What Causes Hyperthyroidism?
Graves’ Disease
Graves’ disease is an autoimmune disorder in which antibodies stimulate the thyroid to produce excessive thyroid hormone.
It is one of the most common causes of hyperthyroidism.
Toxic Thyroid Nodules
One or more thyroid nodules can become overactive and produce thyroid hormone independently of normal regulation.
Thyroiditis
Inflammation of the thyroid may release stored thyroid hormone into the bloodstream.
This is important because antithyroid drugs are generally not useful for thyroiditis in the same way they are for Graves’ disease or toxic nodular hyperthyroidism.
Medicines or Excess Thyroid Hormone
Some medicines, including amiodarone, can affect thyroid function.
Taking more thyroid-replacement hormone than the body needs can also produce symptoms of thyroid-hormone excess.
Can Hyperthyroidism Cause an Actual Arrhythmia?
Yes.
Hyperthyroidism can cause ordinary sinus tachycardia, in which the heart’s normal rhythm simply becomes faster.
But excess thyroid hormone can also increase susceptibility to true rhythm disorders.
The best-established example is atrial fibrillation (AFib).
A 2024 review estimated that atrial fibrillation occurs in approximately 5% to 15% of people with overt hyperthyroidism.
This is one reason doctors routinely consider thyroid dysfunction when evaluating new atrial fibrillation.
Is a Fast Heartbeat From Thyroid Disease Always AFib?
No.
Many people with hyperthyroidism simply have a faster normal sinus rhythm.
Others may experience premature beats or another arrhythmia, and some develop atrial fibrillation.
The sensation alone cannot identify the rhythm.
That is why an ECG or ambulatory rhythm monitor may sometimes be needed.
Can Hypothyroidism Cause Palpitations?
An underactive thyroid more commonly tends to slow heart rate rather than accelerate it.
However, someone being treated with levothyroxine can develop palpitations if the thyroid-hormone dose is higher than their body requires.
Symptoms suggesting excessive thyroid replacement may include:
- Palpitations
- Fast heartbeat
- Tremor
- Anxiety or restlessness
- Sweating
Do not stop or change prescribed thyroid hormone on your own. Thyroid blood tests can help determine whether the dose needs adjustment.
What Thyroid Tests Are Used for Palpitations?
Thyroid testing is particularly useful when palpitations occur together with symptoms suggesting thyroid dysfunction.
TSH
Thyroid-stimulating hormone (TSH) is usually the first blood test used to assess thyroid function in an adult without suspected pituitary disease.
Free T4
When TSH is below the reference range, free T4 is generally measured to determine whether circulating thyroid hormone is elevated.
Free T3
Free T3 is also useful when TSH is low because some people have predominantly elevated T3.
Thyroid Antibodies
TSH-receptor antibodies may help confirm Graves’ disease when thyrotoxicosis is present.
Thyroid Imaging When Needed
Additional testing may help distinguish Graves’ disease, toxic nodules and other causes.
Ultrasound is not automatically required just because thyroid blood tests are abnormal.
Review Supplements
High-dose biotin supplements can interfere with some thyroid tests and produce misleading results.
Tell your healthcare professional about supplements before thyroid testing.
What Do Hyperthyroidism Blood Tests Usually Show?
In typical primary hyperthyroidism, TSH is suppressed below the laboratory reference range.
Free T4, free T3, or both may be elevated.
But the pattern is not always as simple as “low TSH, high T3 and high T4.”
For example, some people have predominantly elevated T3, while in subclinical hyperthyroidism TSH is low but free T4 and free T3 remain within their reference ranges.
Laboratory results therefore need to be interpreted together with symptoms, medicines and the clinical context.
What Heart Tests Might Be Needed?
Finding hyperthyroidism does not automatically tell us what heart rhythm was occurring during a palpitation.
ECG / EKG
An ECG can show sinus tachycardia, atrial fibrillation or other rhythm abnormalities if present during the recording.
Holter or Event Monitor
Intermittent palpitations may require longer monitoring if the office ECG does not capture an episode.
Echocardiogram
Echocardiography may be considered when symptoms or examination raise concern about structural heart disease, persistent AFib or heart failure.
For the broader differential diagnosis, see our cornerstone guide to causes of heart palpitations .
How Are Thyroid-Related Palpitations Treated?
Treatment depends on why thyroid hormone is elevated. There is no single treatment that is correct for every patient.
Will Palpitations Always Disappear After 2–3 Months?
There is no fixed timetable.
Some symptoms may improve relatively quickly, particularly when a beta-blocker is appropriate.
Thyroid hormone levels may take weeks or months to normalize, depending on the condition and treatment.
If palpitations continue after thyroid function has normalized, another cardiac or non-cardiac cause may need to be considered.
Antithyroid Medication Does Not Treat Every Form of Thyrotoxicosis
Drugs such as methimazole reduce the thyroid gland’s ability to make new thyroid hormone.
They are therefore useful for conditions such as Graves’ disease and toxic thyroid nodules.
In thyroiditis, excess hormone may instead result from stored thyroid hormone leaking from inflamed thyroid tissue.
Antithyroid drugs are generally not effective for that mechanism, which is why establishing the cause of thyrotoxicosis is important before choosing treatment.
Does Radioactive Iodine or Surgery Always Mean Lifelong Thyroid Hormone?
It depends on the treatment.
If the entire thyroid gland is surgically removed, lifelong thyroid-hormone replacement is required.
If only part of the thyroid is removed, some patients retain enough thyroid function, while others later need replacement.
Radioactive iodine frequently results in hypothyroidism, particularly when used to definitively treat Graves’ disease, so long-term thyroid-function monitoring is essential.
Can Untreated Hyperthyroidism Damage the Heart?
Persistent uncontrolled hyperthyroidism can place considerable stress on the cardiovascular system.
Potential complications include:
- Persistent tachycardia
- Atrial fibrillation
- Increased systolic blood pressure in some patients
- Worsening of existing heart disease
- Heart failure in susceptible patients
- Rare thyrotoxic cardiomyopathy
However, the old statement that hyperthyroidism inevitably produces an irreversible heart failure syndrome is incorrect.
Thyrotoxic cardiomyopathy is uncommon and can be substantially reversible when the thyroid disorder and associated cardiovascular problems are treated promptly.
What Is Thyroid Storm?
Thyroid storm is a rare but life-threatening complication of severe thyrotoxicosis.
It may involve severe cardiovascular and systemic symptoms such as a very rapid heartbeat, high temperature, agitation or confusion and severe illness.
Suspected thyroid storm requires emergency medical treatment.
Thyroid Testing Is Simple — But Palpitations Still Need Clinical Context
When a patient comes to me with new palpitations, thyroid disease is one of the medical causes I consider.
I become more suspicious when the palpitations occur together with symptoms such as weight loss, tremor, heat intolerance, increased sweating, anxiety or an enlarged thyroid.
But even when thyroid tests are abnormal, I still want to understand what the heart is doing.
Is this simply a faster sinus rhythm? Are there skipped beats? Is the rhythm irregular? Could atrial fibrillation be present?
Treating the thyroid disorder is essential, but persistent or concerning rhythm symptoms should not be ignored simply because we have found a thyroid abnormality.
When Should You See a Doctor?
Arrange medical evaluation if you have palpitations together with:
- Unexplained weight loss
- Tremor or shakiness
- Heat intolerance or excessive sweating
- Persistent anxiety or unusual restlessness
- An enlarged thyroid or neck swelling
- A repeatedly rapid or irregular heartbeat
- New atrial fibrillation
- Palpitations after a thyroid-medication dose change
If dizziness occurs with your heartbeat symptoms, read dizziness and heart palpitations .
When Thyroid-Related Palpitations Need Urgent Care
Seek urgent or emergency medical care if palpitations occur with:
- Chest pain or significant chest pressure
- Fainting or loss of consciousness
- Severe shortness of breath
- Severe dizziness or near-fainting
- Severe weakness or collapse
- A sustained very fast or severely irregular heartbeat with significant symptoms
- Severe illness with high temperature, confusion or agitation in someone with hyperthyroidism
Do not assume that severe symptoms are harmless simply because hyperthyroidism has already been diagnosed.
Thyroid and Heart Palpitations: FAQs
Can an overactive thyroid cause heart palpitations?
Yes. Hyperthyroidism can make the heart beat faster, harder or irregularly and is a recognized medical cause of palpitations.
What do thyroid palpitations feel like?
They may feel like racing, pounding, fluttering, skipped beats or an irregular heartbeat.
The sensation alone cannot tell whether the rhythm is sinus tachycardia, premature beats, atrial fibrillation or another rhythm.
What TSH level causes palpitations?
There is no single TSH value at which every person develops palpitations.
Symptoms depend on the degree and duration of thyroid-hormone excess, age, cardiovascular health and individual susceptibility.
Can hyperthyroidism cause AFib?
Yes. Atrial fibrillation is an important cardiovascular complication of hyperthyroidism.
Research estimates that AFib occurs in roughly 5% to 15% of people with overt hyperthyroidism.
Can hypothyroidism cause a racing heart?
Hypothyroidism more commonly slows the heart rate.
However, excessive thyroid-hormone replacement in someone being treated for hypothyroidism may cause racing, pounding or irregular heartbeats.
Will beta-blockers cure thyroid palpitations?
Beta-blockers can reduce rapid heart rate, tremor and related symptoms in suitable patients.
They generally do not correct the underlying thyroid-hormone excess, so thyroid-specific treatment may still be required.
How quickly do thyroid palpitations go away?
There is no fixed timetable.
Improvement depends on the cause of hyperthyroidism, its severity, treatment chosen, how quickly thyroid levels normalize and whether an independent arrhythmia is also present.
Is a low TSH enough to diagnose hyperthyroidism?
Not by itself.
When TSH is below the reference range, free T4 and free T3 are generally measured to define the thyroid-hormone pattern.
Should I stop levothyroxine if I develop palpitations?
Do not stop or change prescribed thyroid medication on your own.
Contact your healthcare professional. Thyroid-function tests can help determine whether the dose needs adjustment.
Continue Reading
Evidence Used for This Article
- American Thyroid Association. Hyperthyroidism .
- NICE. Thyroid Disease: Assessment and Management .
- NHS. Overactive Thyroid (Hyperthyroidism) .
- Kostopoulos G, Effraimidis G. Epidemiology, Prognosis, and Challenges in the Management of Hyperthyroidism-Related Atrial Fibrillation . European Thyroid Journal. 2024.
- Quiroz-Aldave JE, et al. Thyrotoxic Cardiomyopathy: State of the Art . 2023.
- MedlinePlus. Hypothyroidism and Thyroid-Hormone Replacement .