Yes, your heart rate commonly increases when you are sick. This phenomenon is known as tachycardia, meaning the heart is beating faster than the typical resting rate of 60 to 100 beats per minute. This elevated heart rate is generally a normal and protective response as your body works hard to fight off an infection. The increase in heart rate ensures that the immune system’s resources are delivered efficiently where they are needed most.
The Physiological Reason Heart Rate Increases During Illness
The primary reason your heart speeds up during illness is the body’s biological response to combat pathogens. Fighting an infection activates inflammation, which triggers the sympathetic nervous system, or “fight or flight” mode. This system releases hormones like epinephrine and norepinephrine, which directly stimulate the heart to beat faster and stronger.
A major contributor to this increased heart rate is the heightened metabolic demand caused by a fever. For every one-degree Celsius (1.8°F) rise in body temperature, your body’s metabolic rate increases by approximately 10 to 13%. This demands more oxygen and nutrients, requiring the heart to pump faster to circulate necessary oxygen and immune cells throughout the body.
This relationship, sometimes called Liebermeister’s rule, suggests the heart rate typically increases by about 8 to 10 beats per minute for every degree Celsius rise in temperature. This mechanism also helps dissipate the excess heat generated by the fever through faster circulation near the skin’s surface. The increased heart rate is the cardiovascular system compensating to maintain adequate blood flow and oxygen delivery.
Other Contributors to Heart Rate Changes
While the immune response is the main driver, other factors associated with being sick can contribute to a faster heart rate. Dehydration is a common secondary factor that stresses the cardiovascular system. Reduced fluid intake, coupled with fluid loss from fever, vomiting, or diarrhea, decreases the volume of blood circulating in the body.
To maintain blood pressure and ensure vital organs receive enough oxygenated blood, the heart must compensate by pumping the reduced blood volume more frequently. This strain forces the heart to work harder, causing an elevated heart rate. Proper hydration is an effective way to lessen the burden on your heart when ill.
Medications
Certain common over-the-counter cold and flu remedies can stimulate the nervous system, leading to an increased heart rate. Decongestants, particularly those containing pseudoephedrine or phenylephrine, work by constricting blood vessels to relieve nasal congestion. This vasoconstriction can raise blood pressure, forcing the heart to beat faster to overcome the increased resistance. People with pre-existing heart conditions should be cautious with these medications, as they can exacerbate cardiovascular strain.
When to Monitor and Seek Medical Advice
If you notice a rapid heart rate while sick, it is helpful to monitor it, especially at rest, using a wrist pulse check or a wearable device. A normal resting heart rate for most adults is between 60 and 100 beats per minute.
While a heart rate elevation that correlates with your fever is typically a normal finding, a sustained rate above 100 to 110 beats per minute, or a rate that seems disproportionately fast compared to a mild fever, may warrant medical attention. The most important factor is the presence of other symptoms alongside the rapid heart rate.
You should seek immediate medical advice if your rapid heart rate is accompanied by specific warning signs. These symptoms could indicate that the heart is struggling or that the underlying illness is more severe.
You should seek immediate medical advice if your rapid heart rate is accompanied by:
- Chest pain or discomfort.
- Severe shortness of breath.
- Sudden weakness.
- Fainting or near-fainting spells.
- Dizziness.