Heart rate, the number of times your heart beats each minute, is a fundamental indicator of health. While it fluctuates throughout the day based on activity and emotions, a typical resting heart rate for adults ranges from 60 to 100 beats per minute. Illness can influence this rate, often causing it to change as the body works to combat infection or recover. Understanding these changes offers insights into the body’s condition and when medical attention might be necessary.
The Body’s Response to Illness
When sick, the body initiates an immune response to fight off pathogens, leading to physiological adjustments that affect heart rate. The immune system’s activation requires more energy and blood flow, prompting the heart to pump harder and faster. This increased workload delivers oxygen and immune cells throughout the body and is a normal part of healing.
Fever, a common symptom of illness, directly influences heart rate. For every 1.8°F (1°C) increase in body temperature, the heart rate rises by approximately 10 beats per minute. Dehydration, often accompanying illness due to reduced fluid intake, vomiting, or diarrhea, also contributes to an elevated heart rate. When the body is low on fluids, blood volume decreases, causing the heart to beat faster to maintain blood pressure and ensure adequate blood supply.
Inflammation can also lead to an increased heart rate. The body releases inflammatory mediators to combat infection, which affect the heart’s electrical signals and cause it to beat more rapidly. Stress from being unwell, both physical and emotional, can trigger the sympathetic nervous system, releasing stress hormones like adrenaline that directly increase heart rate.
Understanding Abnormal Heart Rates
While an elevated heart rate is common during illness, it is important to recognize what constitutes an abnormal rate. For adults, a resting heart rate consistently over 100 beats per minute is called tachycardia, or an abnormally fast heart rate. This rapid beating can be a normal physiological response to stressors like exercise, fever, or pain. However, if the heart beats too quickly, it may not fill adequately with blood, potentially reducing its efficiency in supplying oxygen.
Conversely, a resting heart rate below 60 beats per minute for adults is known as bradycardia, or an abnormally slow heart rate. While a slow heart rate can be normal for highly physically fit individuals or during sleep, a consistently low rate not typical for a person can indicate an underlying issue. Both tachycardia and bradycardia can be an irregular heart rhythm, or arrhythmia, where the heart beats too fast, too slow, or with an inconsistent pattern.
When to Seek Medical Care
Monitoring heart rate at home can be done manually by checking your pulse or using wearable devices. While a temporary increase in heart rate during illness is often harmless, certain accompanying symptoms warrant immediate medical attention.
If an altered heart rate, whether fast or slow, is accompanied by chest pain or discomfort, seek immediate medical attention. Shortness of breath is another concerning symptom that, when combined with an abnormal heart rate, suggests the need for medical evaluation. Severe dizziness, lightheadedness, confusion, or fainting spells indicate the body may not be receiving adequate blood flow and oxygen. If your heart rate remains significantly high even at rest, or if you notice an irregular pulse that is new or worsening, seek medical advice.