When to go to the hospital for a fever depends on several factors, including the age of the person, the severity of the fever, and the presence of other symptoms. Here are some general guidelines based on the search results:

• For most adults, a normal body temperature is between 97°F and 99°F, though 98.6°F is generally accepted as the standard of normal.
• A fever is generally defined as a temperature of 100.4°F or higher.
• For patients who are otherwise healthy, alert, and have an obvious explanation for their low-grade fever – such as a cold – at-home remedies and monitoring may be sufficient. However, any fever above 103°F should be treated immediately in the ER.
• If you or your child are experiencing any of the following symptoms in conjunction with a fever, a trip to the ER is warranted: confusion, severe headache, rash, unusual sensitivity to bright light, stiff neck and pain when you bend your head forward, mental confusion, strange behavior or altered speech, persistent vomiting, difficulty breathing or chest pain, abdominal pain, pain when urinating, convulsions or seizures.
• For infants and toddlers, a fever is a particular cause for concern. Call your babys health care provider if your child is younger than 3 months old and has a rectal temperature of 100.4°F (38°C) or higher, or between 3 and 6 months old and has a rectal temperature higher than 102°F (38.9°C) or has a lower temperature but seems unusually irritable, sluggish or uncomfortable.
• Seek emergency care immediately if your fever persists longer than three days, or your body temperature is 103°F or higher, or if you have a compromised immune system, have had chemotherapy recently, or are experiencing other symptoms.
• If an adults fever rises above 105°F, they should seek emergency care.

In summary, if you or your child have a fever and are experiencing any of the symptoms listed above, or if the fever is persisting or rising above 103°F, it is best to seek medical attention.