Fever does not mean presence of infection. There are many situations where there may be fever without infection. Such fevers do not need antibiotics.

1. Sepsis is a clinical syndrome, which results from the dysregulation of inflammatory response to an infection. The temperature is between 36°C to 38.30°C. Heart rate is often more than 90 per minute.
2. Symptomatic inflammatory response syndrome (SIRSI means a clinical syndrome, which results from dysregulated inflammatory response to any infections such as inflammation of the pancreas, inflammation of the vessels, clot formations in the veins.
3. Many antibiotics can cause fever; unless they are discontinued, fever will not subside.
4. Hyperthermia is a condition with elevated body temperature but it is not called fever. Examples are exposure to heat or heat stroke and in response to anesthetic drugs and anti-psychotic drugs.
5. Hyperthermia may not respond to anti–fever drugs.
6. When fever is more than 41.5°C, it is acute hyperpyrexia.
7. Hyperpyrexia is usually seen in patients with severe infections but it may also occur in brain hemorrhage. It responds to anti–fever drugs.
8. High temperature without infection is found in case of a hyperfunctioning thyroid gland.
9. Recreational drugs such as Ecstasy can also cause fever without any infection.
10. Mild fever can also occur after exertion.