A low-grade fever is generally defined as a body temperature slightly above normal but below the threshold of a high fever. Most sources agree that a low- grade fever falls roughly within the range of about 99.5°F (37.5°C) to 100.3–100.4°F (37.9–38.0°C)

. Some definitions extend low-grade fever up to around 102.2°F (39°C), but this is less common and sometimes considered moderate-grade fever instead

. Key points about low-grade fever:

• Normal body temperature is about 98.6°F (37°C), but it varies by person, time of day, and measurement method

• Low-grade fever indicates mild activation of the immune system, often due to infections like colds or flu

• Symptoms accompanying a low-grade fever may include chills, sweating, headache, muscle aches, fatigue, flushed face, and feeling warm or feverish

• Low-grade fevers usually do not require treatment unless accompanied by other concerning symptoms or occurring in very young infants

• Persistent low-grade fever lasting more than a few days may warrant medical evaluation, especially if other symptoms develop

In summary, a low-grade fever is a mild elevation in body temperature, typically from about 99.5°F to 100.3–100.4°F, signaling a mild immune response, often to infection, and usually not serious on its own