A common experience when feeling unwell is noticing that your heart seems to be beating faster than usual. Your heart rate, measured in beats per minute (bpm), is how many times your heart contracts in one minute. A normal resting heart rate for adults is typically 60 to 100 bpm. While a faster heart rate can be concerning, it’s often a natural response as your body fights illness.
How Illness Affects Heart Rate
When your body fights an infection, its internal systems work harder to restore health. This increased effort directly influences your heart rate. The heart’s primary role is to circulate blood, delivering oxygen and nutrients while removing waste.
Fever is a common reason for an elevated heart rate during sickness. As body temperature rises, your metabolic rate increases, meaning your body needs more energy and oxygen. To meet this demand, your heart pumps blood more frequently and forcefully. For every 1 degree Fahrenheit (0.56 degrees Celsius) increase, your heart rate can rise by about 10 beats per minute, helping distribute heat and oxygen.
The immune response also increases heart rate. When fighting infection, your immune system releases signaling molecules like cytokines, influencing the cardiovascular system. This inflammatory process signals your heart to pump more blood, delivering immune cells and resources.
Other Contributors to Elevated Heart Rate
Beyond direct physiological responses, other factors associated with illness can also increase your heart rate, often compounding the effects of the immune response.
Dehydration often accompanies illness, especially with symptoms like fever, vomiting, or diarrhea. When your body loses fluids, blood volume decreases. To maintain blood pressure and oxygen delivery, your heart pumps faster to circulate the reduced blood volume. Staying hydrated supports your heart’s function during sickness.
The psychological and physical stress of being sick can also elevate your heart rate. Illness triggers the body’s stress response, activating the sympathetic nervous system and releasing stress hormones like adrenaline. This “fight-or-flight” response naturally speeds up your heart.
Certain medications for cold and flu symptoms can also impact heart rate. Over-the-counter decongestants, for example, often contain ingredients like pseudoephedrine or phenylephrine, which can have stimulant effects, narrowing blood vessels and raising heart rate and blood pressure. Other medications, including some pain relievers, asthma medications, and certain antibiotics, may also cause an increased heart rate as a side effect.
Recognizing When to Seek Medical Advice
While an elevated heart rate is often normal when sick, it’s important to know when it signals a serious concern. A normal increase due to fever usually resolves as the fever subsides. However, if your heart rate remains consistently high, above 100 bpm, even at rest and without a clear cause like fever, seek medical attention.
Specific warning signs, when accompanied by a fast heart rate during illness, indicate the need for prompt medical evaluation. Seek immediate medical attention if you experience chest pain or discomfort, shortness of breath, dizziness, lightheadedness, or fainting. A very rapid or irregular heartbeat, or a feeling of fluttering or pounding in your chest, also requires assessment by a healthcare professional. Individuals with pre-existing heart conditions should be particularly cautious and consult their doctor if they notice significant heart rate changes when sick. Rest and good hydration can help manage illness.