Temperature How High See Doctor Age Four. See a doctor within 24 hours if your child has a fever and:. Your child is age 3 to 6 months and has a temperature up to 102 f (38.9 c) and seems unusually irritable, lethargic or uncomfortable, or has a temperature higher than 102 f (38.9 c).
New research shows that forehead temps may also be accurate under 3 months of age. A cough that produces yellow, green, tan, or bloody mucus 2. In a child older than 3 months but younger than 2 years old, call the doctor or visit the hospital if the fever has persisted for longer than 24 hours.