A fever is an increase in the body's temperature. It is usually defined as a temperature of 100.4°F (38°C) or higher. Brief mild or moderate fevers generally have no long-term effects, and they often do not need treatment. Moderate or high fevers may make you feel uncomfortable and can sometimes be a sign of a serious illness or disease. The sweating that may occur with repeated or prolonged fever may also cause a loss of fluid in the body (dehydration).

• Age.
• Time of day.
• Where in the body you take the temperature. Readings may vary if you place the thermometer:
  • In the mouth (oral).
  • In the rectum (rectal).
  • In the ear (tympanic).
  • Under the arm (axillary).
  • On the forehead (temporal).

Follow these instructions at home:

Medicines

• Take over-the counter and prescription medicines only as told by your health care provider. Follow the dosing instructions carefully.
• If you were prescribed an antibiotic medicine, take it as told by your health care provider. Do not stop taking the antibiotic even if you start to feel better.

General instructions

• Watch your condition for any changes. Let your health care provider know about them.
• Rest as needed.
• Drink enough fluid to keep your urine pale yellow. This helps to prevent dehydration.
• Sponge yourself or bathe with room-temperature water to help reduce your body temperature as needed. Do not use ice water.
• Do not use too many blankets or wear clothes that are too heavy.
• If your fever may be caused by an infection that spreads from person to person (is contagious), such as a cold or the flu, you should stay home from work and public gatherings for at least 24 hours after your fever is gone. Your fever should be gone without the need to use medicines.

Contact a health care provider if:

• You vomit.
• You cannot eat or drink without vomiting.
• You have diarrhea.
• You have pain when you urinate.
• Your symptoms do not improve with treatment.
• You develop new symptoms.
• You develop excessive weakness.

Get help right away if:

• You have shortness of breath or have trouble breathing.
• You are dizzy or you faint.
• You are disoriented or confused.
• You develop signs of dehydration, such as:
  • Dark urine, very little urine, or no urine.
  • Cracked lips.
  • Dry mouth.
  • Sunken eyes.
  • Sleepiness.
  • Weakness.
• You develop severe pain in your abdomen.
• You have persistent vomiting or diarrhea.
• You develop a skin rash.
• Your symptoms suddenly get worse.

Summary

• A fever is an increase in the body's temperature. It is usually defined as a temperature of 100.4°F (38°C) or higher. Moderate or high fevers can sometimes be a sign of a serious illness or disease. The sweating that may occur with repeated or prolonged fever may also cause dehydration.
• Pay attention to any changes in your symptoms and contact your health care provider if your symptoms do not improve with treatment.
• Take over-the counter and prescription medicines only as told by your health care provider. Follow the dosing instructions carefully.
• If your fever is from an infection that may be contagious, such as cold or flu, you should stay home from work and public gatherings for at least 24 hours after your fever is gone. Your fever should be gone without the need to use medicines.
• Get help right away if you develop signs of dehydration, such as dark urine, cracked lips, dry mouth, sunken eyes, sleepiness, or weakness.