- Oral (mouth) temperature above 100ºF (37.8ºC)
- Armpit temperature above 99ºF (37.2ºC)
- Ear temperature above 100.4ºF (38ºC) in rectal mode or 99.5ºF (37.5ºC) in oral mode
- Forehead temperature above 100.4ºF (38ºC)
- Rectal temperature above 100.4ºF (38ºC)
What is the best way to take my temperature? — Armpit, ear, and forehead temperatures are easier to measure than rectal or oral temperatures, but they are not as accurate.
Here is the right way to take an oral temperature:
- Wait at least 30 minutes after you eat or drink anything hot or cold.
- Wash the thermometer with cool water and soap. Then rinse it.
- Place the tip of the thermometer under your tongue toward the back. Hold the thermometer with your lips, not your teeth.
- Keep your lips closed around the thermometer. A glass thermometer takes about 3 minutes to work. Most digital thermometers take less than 1 minute.
The height of the temperature is less important than how sick you feel. If you think you have a fever and you feel sick, your doctor or nurse might want you to double-check by getting an oral or rectal temperature.
What causes fever? — The most common cause of fever in adults is infection. Common infections that can cause fever include:
- A cold or the flu
- An airway infection, such as bronchitis
- A stomach bug
Most of these infections are not serious and get better on their own.
When should I see a doctor or nurse? — Call your doctor or nurse if you get a fever and you:
- Are pregnant
- Recently got back from a trip to Africa, Asia, or Latin America
- Just got out of the hospital, or had surgery or another medical procedure
- Get infections often
- Are on chemotherapy – Call your doctor or nurse if your oral temperature goes above 100ºF (37.8ºC) for more than 1 hour. Also call if it goes above 101ºF (38.3ºC) even just 1 time.
You should also call if you have:
- Fever that lasts several days or keeps coming back
- A recent bite from an insect called a tick – Infections you can catch from tick bites can cause fever and other symptoms.
- A serious health condition, such as diabetes, heart disease, cancer, lupus, or sickle cell anemia
- Fever plus 1 or more of these symptoms:
- Trouble breathing
- Severe headache or neck pain
- Seizure or confusion
- Severe vomiting or diarrhea
- Severe pain in the belly, back, or sides
- Any other symptom that is unusual or worries you
Will I need tests? — Maybe. Your doctor or nurse will do an exam and talk with you about your symptoms. You might also have the following tests:
- Blood tests
- Urine tests
- Chest X-ray or CT scan – These imaging tests create pictures of the inside of the body.
Your doctor or nurse will talk to you about any other tests you might need.
Can I do anything on my own to feel better? — Yes. You can stay home, rest, and drink plenty of fluids. You can also take acetaminophen (sample brand name: Tylenol) to relieve fever.
How are fevers treated? — That depends on the cause. Many people do not need treatment. If you do, treatments can include:
- Antibiotics to fight the infection. But antibiotics only work on infections caused by bacteria, not infections caused by viruses. For example, antibiotics will NOT work on a cold.
- Medicines, such as acetaminophen (sample brand name: Tylenol) or ibuprofen (sample brand names: Advil, Motrin). These medicines can help bring down a fever. But they are not always necessary.