To know if you have a fever, the most accurate way is to measure your body temperature with a thermometer. A fever is generally defined as a body temperature of 100.4°F (38°C) or higher. There are several types of thermometers you can use, including oral, ear, rectal, and forehead thermometers, with oral and rectal thermometers generally being the most accurate. If you don't have a thermometer, you can look for signs such as:
- Feeling unusually hot or flushed, especially in your cheeks
- Shivering or chills
- Sweating
- Headache, muscle aches, or fatigue
- Loss of appetite
- Warm skin that feels hotter than usual on your chest or back
- Other symptoms like sore eyes or swollen lymph nodes
Additional signs of possible fever in infants or young children include irritability, lethargy, flushed skin, difficulty drinking, or feeding. A fever indicates your immune system is fighting an infection and usually resolves on its own. However, if the fever is very high (above 104°F or 40°C in adults) or persistent, or if it's in infants under 2 months old, medical advice should be sought. In summary, checking with a thermometer remains the best method, supported by these physical signs and symptoms.
