5 reasons being sick can cause a high heart rate

I’d been unusually tired for a couple of days. Waking up on the third day, I knew I had some sort of stomach bug. I crawled out of bed, brushed my teeth, changed into some cozy loungewear and wandered out to the couch. Glancing at my fitness watch, I was surprised to find it had rewarded me with 21 activity minutes (based on elevated heart rate) for those decidedly non-athletic movements. Somewhat concerned, I wondered if I was sicker than I thought or if I needed to call a doctor. Here’s what I found out about how being sick can cause a high heart rate.

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What is a normal heart rate?

Your heart rate, or pulse, is how fast your heart is beating at any given moment. According to the American Heart Association (AHA), a normal resting heart rate for healthy adults is between 60 and 100 beats per minute (bpm). Resting heart rate is a measure of how much blood your body pumps when you’re still and relaxed (but not ill). Some people may have a resting heart rate below 60 and as low as 40, which can be normal for them. It may indicate that they get a lot of physical activity, are very athletic, or take a heart-regulating medication such as a beta blocker.

For newborns and children through nine years old, see this National Institutes of Health article for resting heart rate norms at different ages. Children 10 years of age and older will typically fall into the adult range of 60 to 100 bpm.

If you don’t have a fitness watch, the AHA suggests the easiest places to find your pulse include your wrists, inside of your elbow, side of your neck and top of your foot. To get the most accurate reading, place a finger over your pulse and count the number of beats for a full 60 seconds.

If you notice that your heart is pounding, racing, fluttering or otherwise behaving abnormally for more than a few minutes, you should see your healthcare provider. 

Why your heart rate goes up when you’re sick

If you ever have an experience like mine, you’ll be glad to know that it can be completely normal for your heart rate to go up when you’re sick. More than likely, it’s not a cause for concern. However, if you’re not sure or you’re having other worrying symptoms, be sure to get it checked out.

Here are some reasons why your heart might beat faster when you’re sick:

• Infections: Common viral or bacterial infections, such as flu, COVID-19 and norovirus, can cause your heart rate to increase. Most people over the age of six months should get an annual flu shot to help prevent complications of influenza. Likewise, staying updated on COVID-19 vaccinations can help prevent complications of a coronavirus infection. Here are the CDC’s COVID-19 vaccine recommendations.
• Fever: When your body temperature rises, so does your heart rate. Fever — especially a high fever — can cause your heart to beat faster. Read our blog to know when fever is an emergency.
• Dehydration: When you don’t drink enough fluids, your blood thickens and your body works harder to pump oxygen. Symptoms of severe dehydration include rapid heartbeat and breathing. Dehydration can be a life-threatening condition that should be treated immediately. Be sure to get plenty of liquids (water is best) when you’re sick.
• Stress or anxiety: It probably won’t come as a surprise that emotional or physical stress can increase your heart rate and blood pressure. If left untreated, over time stress can lead to several different types of heart disease, including arrhythmias (abnormal heart rhythms). If you’re feeling depressed or anxious, Medical City Healthcare’s Mental Health Helpline can offer support and guidance.
• Medications: Just as beta blockers tend to slow your pulse, some medications can have the opposite effect and raise your heart rate. These can include prescription or over-the-counter drugs used to treat asthma and allergies, coughs and colds, thyroid conditions, depression and more. Be sure to alert your healthcare provider if you think one of your medications is causing changes in your heart rate or rhythm.

In my case, by Monday morning I felt fine. My smartwatch no longer gave me freebie activity minutes, and I was ok with that.

Take our free online heart health risk assessment for an easy-to-understand snapshot that can help you manage your heart health.

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