When should I take my child to the hospital for a fever?

What the evidence says

Age matters a lot. Babies younger than 3 months with any fever (38.0°C/100.4°F or higher, measured rectally) should be seen urgently, because young infants can get seriously ill quickly and it's hard to tell which ones have a dangerous infection just by looking at them. Babies 3 to 6 months old with a fever should also see a doctor. Beyond 6 months, how your child looks and acts usually matters more than the number on the thermometer.

For older babies and children, go to the emergency department (or call your doctor right away) if they seem very unwell or unusually drowsy or hard to wake, are working hard to breathe or breathing fast, have a stiff neck or severe headache, have a rash that doesn't fade when you press a glass against it, are vomiting repeatedly, show signs of dehydration (no wet diaper/urine for many hours, no tears, sunken soft spot), have had a feverish seizure, or have a weakened immune system (like sickle cell disease, cancer treatment, or steroid use).

For a child over 6 months who is drinking fluids and seems reasonably well between fever spikes, home care with fluids and rest is usually fine. Still check in with your doctor if the fever lasts more than 48 to 72 hours, or if new worrying symptoms appear.

Remember: how high the fever is doesn't tell you how sick your child is — a child with a mild illness can have a very high fever, while a child with a serious infection sometimes has none.