A fever is a temporary elevation in body temperature, signaling that the body is actively fighting an infection or illness. While a fever can cause discomfort, it is not a cause for alarm in most healthy children and adults, often resolving within a few days. This article explains when a fever indicates a need for medical attention, including when a hospital visit may be necessary.
Understanding Fever Basics
Body temperature can be measured orally, rectally, axillary, tympanic, and temporal artery. Rectal and oral measurements generally provide the most accurate assessment of core body temperature. A temperature of 100.4°F (38°C) or higher, when measured orally, is typically considered a fever. Rectal and ear thermometers may read about 0.5 to 1°F (0.3 to 0.6°C) higher than oral readings, while armpit and forehead readings may be lower.
Fevers commonly result from infections, with viral infections being a frequent cause, such as colds or the flu. Bacterial infections, like strep throat or urinary tract infections, can also trigger a fever. Beyond infections, a fever can arise from inflammatory conditions, certain medications, or even immunizations. The body’s hypothalamus, acting as its “thermostat,” adjusts the body temperature upward in response to these factors, initiating processes like shivering to generate heat.
Fever in Infants and Young Children
Newborns (0-3 months)
Any fever in a newborn, defined as a rectal temperature of 100.4°F (38°C) or higher, requires an emergency department visit. A newborn’s immune system is still developing, making them highly vulnerable to serious infections that can worsen rapidly. Even without other symptoms, a fever at this age is a serious concern. Parents should also seek emergency care if a newborn’s fever is accompanied by difficulty waking up to feed, difficulty breathing, a rash, vomiting, or inconsolable crying. Because their temperature regulation system is not fully developed, newborns can also get overheated easily.
Infants (3-6 months)
For infants 3 to 6 months old, a fever above 102°F (38.9°C) warrants a call to your pediatrician. If the infant has a lower temperature but appears unusually irritable, sluggish, or uncomfortable, medical advice should also be sought. It is generally recommended to offer extra fluids like formula or breastmilk and dress the infant in light clothing.
Older Infants and Toddlers (6 months to 2 years)
In older infants and toddlers aged 6 months to 2 years, a rectal temperature higher than 102°F (38.9°C) that persists for more than a day, without other symptoms, should prompt a call to the healthcare provider. If other symptoms like a runny nose, cough, or diarrhea are present, contact the doctor sooner. A fever in this age group may also trigger febrile seizures, which involve temporary shaking or stiffening of the body. Immediate medical attention is necessary for these age groups if the fever is accompanied by a rash, inconsolable crying, difficulty breathing, a stiff neck, persistent vomiting or diarrhea, or signs of dehydration such as fewer wet diapers or a sunken soft spot on the head. If a child appears listless, confused, or has poor eye contact, these are also concerning signs.
Fever in Older Children and Adults
For school-aged children, teenagers, and adults, a sustained fever over 103°F (39.4°C) generally warrants concern and a call to a healthcare provider. While fevers under this threshold are often manageable at home, monitoring for accompanying symptoms is important. Most fevers with viral illnesses in children typically range between 101°F and 104°F (38.4°C and 40°C) and may last for two to three days.
Immediate medical attention is advised if a fever in older children or adults is accompanied by severe headache, a rash that doesn’t fade when pressed, unusual sensitivity to bright light, or a stiff neck with pain when bending the head forward. Other concerning symptoms include mental confusion, strange behavior, altered speech, persistent vomiting, difficulty breathing, chest pain, or severe abdominal pain. Seizures and signs of dehydration, such as reduced urination, also indicate a need for prompt medical evaluation.
Fever in Vulnerable Individuals
Individuals with compromised immune systems or certain underlying health conditions should approach a fever with increased caution, as even a low-grade fever can indicate a serious infection. This includes people undergoing chemotherapy or radiation treatment, where a low neutrophil count can increase infection risk. Corticosteroids, sometimes used in treatment, can also mask a fever. People with chronic diseases such as diabetes, heart disease, kidney disease, or autoimmune disorders like lupus or rheumatoid arthritis, are also considered vulnerable. Additionally, those who have recently undergone surgery or an organ transplant are at a heightened risk of infection. For these individuals, prompt medical evaluation for any fever is recommended to rule out serious complications.
General Guidelines for Seeking Medical Attention
Severe difficulty breathing, sudden onset of confusion, seizures, loss of consciousness, or inability to move a limb are red-flag symptoms that apply across all age groups and warrant immediate emergency care. If a seizure lasts longer than five minutes or a child does not recover quickly afterwards, emergency services should be contacted. While waiting for medical help, it is important to stay hydrated by drinking plenty of fluids like water, electrolyte solutions, or broth. Rest is also beneficial as it assists the body in fighting off infection. Avoid certain medications without consulting a doctor, especially aspirin in children, due to the risk of Reye syndrome. This information serves as guidance and is not a substitute for professional medical advice, so always consult a healthcare provider for personalized recommendations.