A fever in children indicates an elevation in the body’s core temperature, often defined as 100.4°F (38°C) or higher. This response is part of the body’s natural defense mechanism to combat infections. An increased heart rate commonly accompanies this elevated temperature. The heart rate, a vital sign, naturally adjusts to the body’s changing demands during illness.
How Fever Affects a Child’s Heart Rate
When a child develops a fever, the body’s metabolic rate increases as it works harder to fight off the infection. This heightened metabolic activity demands more oxygen and nutrients for the body’s cells. To meet this increased demand, the heart responds by pumping blood more rapidly, resulting in an elevated heart rate.
The body also attempts to dissipate excess heat during a fever. This involves increasing blood flow to the skin, allowing heat to escape. The heart must work harder to circulate this increased volume of blood, further accelerating heartbeats. This faster heart rate is a physiological adaptation to support the immune response and regulate body temperature.
Typical Heart Rate Ranges for Children with Fever
A child’s heart rate naturally varies with age, even when healthy and at rest. For infants under 1 year, a typical resting heart rate without fever ranges from 100 to 160 beats per minute (bpm). Toddlers aged 1 to 3 years generally have a resting heart rate between 90 and 150 bpm, while preschoolers (3 to 5 years) usually fall between 80 and 140 bpm. School-aged children (6 to 12 years) often exhibit resting heart rates from 70 to 120 bpm, and adolescents (13 to 18 years) typically range from 60 to 100 bpm.
When a child has a fever, these resting heart rates will naturally increase. A general guideline is that for every degree Celsius (1.8 degrees Fahrenheit) rise in body temperature, a child’s heart rate may increase by 10 to 20 bpm. For instance, an infant with a fever might see their heart rate rise to 120-180 bpm, while a school-aged child’s heart rate could be 90-140 bpm. Individual responses can vary based on the fever’s severity, underlying cause, and the child’s overall health.
When to Seek Medical Advice for Your Child’s Heart Rate
While an elevated heart rate is expected with fever, certain signs warrant medical attention. Seek immediate medical advice if your child exhibits difficulty breathing (rapid or labored breathing, flaring nostrils, or retractions of the chest). Lethargy, excessive sleepiness, or an inability to be roused are also concerning indicators. Poor feeding in infants or significant decrease in urine output, suggesting dehydration, should prompt a medical evaluation.
Be alert for a persistent very high heart rate that seems disproportionate to the fever, or if your child’s lips or skin appear bluish. Severe pain, unresponsiveness, or if your child “doesn’t look right” to you are reasons to contact a healthcare provider. To check your child’s pulse, gently place two fingers (not your thumb) on the side of their neck, on their wrist, or on the top of their foot, and count the beats for 15 seconds, then multiply by four to get the beats per minute.