Hashimoto's and Heart Palpitations: Could Your Thyroid Be the Cause?

You're sitting quietly on the couch or trying to fall asleep when you suddenly feel it. A strong thump in your chest. Your heart seems to race, skip a beat, or beat irregularly for a moment.

Heart palpitations can be frightening, especially when they happen while you're resting.

If you have Hashimoto's, you may wonder whether your thyroid is causing them. That's possible. Thyroid hormones influence heart rate and rhythm.

But heart palpitations have many possible causes. They don't automatically mean Hashimoto's is responsible or that your thyroid condition is getting worse.

What Are Heart Palpitations?

Heart palpitations are sensations that make you unusually aware of your heartbeat.

You might feel your heart racing, pounding, fluttering, skipping a beat, or beating irregularly.

Some people notice these sensations in their chest, while others feel them in their throat or neck.

The sensation alone doesn't tell you exactly what's happening to your heart rhythm.

Sometimes the heart is genuinely beating faster or irregularly. At other times, you're simply more aware of a normal heartbeat.

That's why it matters how often palpitations happen, how long they last, and whether you experience other symptoms.

Why Can Thyroid Problems Cause Heart Palpitations?

Thyroid hormones affect metabolism, heart rate, and the cardiovascular system.

When too much thyroid hormone is available, your heart may beat faster.

You might also experience trembling, sweating, heat intolerance, restlessness, or unintentional weight loss.

That's why thyroid function may be checked when heart palpitations could be related to thyroid hormone levels.

Blood tests such as TSH and free T4 (FT4) can help assess whether thyroid hormone deficiency or excess may be contributing.

Doesn't Hashimoto's Usually Cause an Underactive Thyroid?

Yes. Hashimoto's is a common cause of hypothyroidism, also known as an underactive thyroid.

With significant hypothyroidism, a slower heart rate may occur.

However, people with Hashimoto's can still experience heart palpitations.

There are several possible explanations.

Sometimes thyroid hormone levels become temporarily elevated. A thyroid medication dose that's higher than your body needs may also contribute.

Palpitations can also occur for reasons unrelated to the thyroid, including caffeine, stress, anemia, or a heart rhythm disorder.

So Hashimoto's and heart palpitations can occur together without necessarily having a direct connection.

What Is Hashitoxicosis?

In Hashimoto's, the autoimmune process can damage thyroid tissue.

Sometimes this damage causes stored thyroid hormones to be released into the bloodstream.

This may temporarily lead to excessive thyroid hormone levels, a phase sometimes called hashitoxicosis.

During this period, symptoms may resemble those of an overactive thyroid, including heart palpitations, a rapid heartbeat, trembling, and heat intolerance.

Hashitoxicosis doesn't happen to everyone with Hashimoto's.

Having palpitations doesn't automatically mean you're experiencing this phase. Appropriate medical assessment and blood tests are needed to determine whether it could be involved.

Can Levothyroxine Cause Heart Palpitations?

Yes. If you take levothyroxine, your dose is an important consideration.

Levothyroxine replaces the thyroid hormone T4.

If your dose is higher than your body needs, you may have too much thyroid hormone available.

This can cause symptoms such as palpitations, a rapid heartbeat, trembling, sweating, restlessness, sleep difficulties, and feeling unusually hot.

If you develop new palpitations after your levothyroxine dose has been increased or changed, discuss this with your healthcare professional.

It doesn't automatically mean your dose is too high. Other explanations remain possible.

Don't stop or reduce your medication without medical advice.

Blood tests can help your healthcare professional assess whether your thyroid levels and medication dose are appropriate.

Heart Palpitations With Normal TSH and FT4

Perhaps you've had your thyroid blood tests checked and both TSH and FT4 are within their reference ranges.

Yet you're still experiencing palpitations.

This can happen.

When thyroid function is appropriate, thyroid hormone deficiency or excess becomes a less likely explanation.

Other possible causes include stress, anxiety, caffeine, nicotine, alcohol, poor sleep, dehydration, fever, anemia, certain medications, hormonal changes, and heart rhythm disorders.

Sometimes palpitations are harmless. In other situations, further investigation is needed.

New, recurring, or worsening symptoms deserve medical attention, especially when other symptoms occur alongside them.

Why Do You Notice Palpitations at Rest or in Bed?

You may barely notice your heartbeat during the day, but once you're lying quietly in bed, every beat seems unusually noticeable.

This doesn't necessarily mean your heart only beats abnormally when you're resting.

When you're lying still, there are fewer distractions and movements competing for your attention. That can make your heartbeat easier to feel.

Body position may also make an extra beat or stronger heartbeat more noticeable.

However, recurring palpitations at rest shouldn't automatically be dismissed as stress.

If they're new, frequent, or accompanied by other symptoms, discuss them with your healthcare professional.

Can Coffee Cause Heart Palpitations?

Caffeine can trigger palpitations or a faster heartbeat in some people.

That doesn't mean everyone with Hashimoto's needs to avoid coffee.

Sensitivity to caffeine varies considerably.

If you notice that palpitations often happen after coffee, energy drinks, or other caffeinated products, it may help to look for a pattern.

The amount matters too. One cup of coffee may affect you differently from several strong coffees or energy drinks.

If caffeine clearly makes your symptoms worse, reducing your intake may be helpful.

Can Stress and Anxiety Cause Palpitations?

Yes. During stress or anxiety, the body releases hormones such as adrenaline.

This can increase your heart rate and make your heartbeat feel stronger.

Sometimes this creates a difficult cycle.

You notice a palpitation, become frightened, and feel more tense. That tension may make your heartbeat even more noticeable, which increases your fear.

This doesn't mean the symptoms are imaginary.

The physical sensations are real.

But stress and anxiety can influence both your heart rate and how strongly you notice it.

At the same time, not every palpitation should automatically be attributed to anxiety. New or recurring symptoms may need medical assessment.

Can Anemia Cause Heart Palpitations?

Yes. Anemia can also cause palpitations.

When you have anemia, your blood may carry less oxygen than your body needs. Your heart may respond by beating faster.

Other symptoms can include fatigue, shortness of breath, dizziness, pale skin, or reduced exercise tolerance.

If you experience palpitations alongside symptoms that could suggest anemia, your healthcare professional can decide whether blood testing is appropriate.

This is one example of why not every symptom in someone with Hashimoto's is necessarily caused by the thyroid.

Can Hormonal Changes Play a Role?

Hormonal changes can affect how people experience their heartbeat.

Heart palpitations are sometimes reported during perimenopause and menopause.

Because menopausal symptoms, thyroid problems, and other medical conditions can overlap, identifying the cause isn't always straightforward.

If you're also experiencing changes in your menstrual cycle, sleep, or temperature regulation, discussing these symptoms together with your healthcare professional may help.

What Should You Track if You Have Palpitations?

If palpitations happen occasionally, a short record may help identify patterns.

You could note what you were doing, how long the episode lasted, and whether your heartbeat felt fast, strong, or irregular.

Caffeine, alcohol, medications, recent levothyroxine dose changes, and other symptoms may also be relevant.

You don't need to monitor your heart rate throughout the entire day.

The aim is to collect useful information when symptoms occur, so you can describe them more clearly to your healthcare professional.

Should You Measure Your Heart Rate?

When you experience palpitations, it can sometimes help to know whether your heart rate is actually fast.

A smartwatch or heart rate monitor may provide useful information.

However, these devices cannot reliably diagnose or rule out every type of heart rhythm disorder.

Try not to check your pulse or smartwatch constantly, particularly if doing so increases your anxiety.

If palpitations recur, a healthcare professional may assess your heart rate and rhythm.

Depending on your symptoms, an electrocardiogram (ECG) or longer heart rhythm monitoring may be recommended.

What Can You Do When You Feel Palpitations?

If you experience palpitations, stop what you're doing for a moment and sit down if that feels comfortable.

Notice what you're experiencing.

Does your heart feel strong, fast, or irregular? How long does it last? Are there any other symptoms?

Slow, calm breathing may help when fear or tension makes the sensations more intense.

However, relaxation shouldn't replace medical assessment when warning signs are present.

When Should You See a Doctor About Palpitations?

Make an appointment with your healthcare professional if palpitations are new, happen repeatedly, become more frequent, or last a long time.

You should also discuss them if they begin after a thyroid medication change or occur alongside other new symptoms.

Your healthcare professional may assess your heart rate, heart rhythm, medications, and other possible causes.

For someone with Hashimoto's or another thyroid condition, TSH and FT4 may be part of that evaluation.

When Should You Seek Urgent Medical Help?

Heart palpitations aren't always dangerous, but some situations require immediate attention.

Seek emergency medical help if palpitations occur with chest pain or pressure, severe shortness of breath, fainting, or sudden severe dizziness.

A persistently very rapid or clearly irregular heartbeat that doesn't settle also needs prompt medical assessment.

Don't try to determine on your own whether Hashimoto's is responsible for severe or sudden symptoms.

Do Palpitations Mean Your Hashimoto's Is Getting Worse?

Not automatically.

A period of heart palpitations doesn't necessarily mean the autoimmune process has become more active or that your thyroid is becoming more damaged.

There are too many possible causes for palpitations to draw that conclusion.

It's more useful to consider your thyroid blood tests, medication, caffeine intake, possible anemia, symptom patterns, and any other health concerns.

These provide more useful clues than assuming every palpitation is directly related to Hashimoto's.

Take Palpitations Seriously Without Assuming the Worst

Feeling your own heartbeat unusually strongly can be frightening.

Fortunately, heart palpitations don't always have a serious cause.

But the sensation alone can't reliably tell you why they're happening.

Your thyroid function may play a role. Your levothyroxine dose may also be relevant. And there are many other possible explanations.

If palpitations are new, recurring, or accompanied by other symptoms, discuss them with a healthcare professional.

By considering the whole picture rather than automatically attributing everything to Hashimoto's, you can work toward a clearer understanding of what's causing your symptoms.