A fever is usually your body fighting an infection. How to measure it, how to make yourself more comfortable, and the temperatures and symptoms that mean you should get help.
What counts as a fever?
Normal body temperature is around 97–99°F (36.1–37.2°C) and changes a little through the day. For adults, a temperature of 100.4°F (38°C) or higher is generally treated as a fever.
| Temperature (by mouth) | What it usually means |
|---|---|
| 99–100.3°F (37.2–37.9°C) | Slightly raised – usually not a fever |
| 100.4–102.9°F (38–39.4°C) | Fever – usually fine to manage at home if you otherwise feel well enough |
| 103°F (39.4°C) or higher | High fever – call your doctor |
A fever is a sign, not an illness. Most fevers in adults come from common infections such as colds, flu, COVID-19 or a urinary tract infection, and pass within a few days.
How to take your temperature
- Use a digital thermometer under your tongue, with your lips closed, until it beeps.
- Wait at least 15 minutes after eating, drinking, smoking or exercise, which can change the reading.
- Readings taken under the arm are usually a little lower than by mouth. Forehead and ear thermometers are fine if you follow their instructions.
- Write down the time and temperature, so you can tell your doctor how the fever has changed.
Should you bring a fever down?
A fever helps your body fight infection, so you don't have to treat it. Treating it is about feeling more comfortable:
- Rest and drink plenty of fluids – fever makes you lose water faster.
- Wear light clothing and use a light blanket. Don't try to "sweat it out" under heavy covers.
- A lukewarm (not cold) shower or sponge bath can help. Avoid ice baths and rubbing alcohol.
If you feel unwell, an over-the-counter fever reducer can help:
| Acetaminophen | Ibuprofen | |
|---|---|---|
| Good for | Fever and aches; gentle on the stomach | Fever, aches and inflammation |
| Take | As the label says, no more than the daily maximum | As the label says, with food or milk |
| Be careful if you | Drink 3 or more alcoholic drinks a day, or have liver disease | Have stomach ulcers or bleeding, kidney disease, heart disease or high blood pressure, take blood thinners, or are in the last months of pregnancy |
Many cold and flu medicines already contain acetaminophen, so check labels to avoid taking a double dose. Never give aspirin to children or teenagers with a fever – it's linked to Reye's syndrome, a rare but serious illness.
When to see a doctor
Call your doctor if:
- Your temperature is 103°F (39.4°C) or higher
- A fever lasts more than 3 days
- You have a weakened immune system (for example from chemotherapy or an organ transplant), had surgery recently, or have just traveled abroad
- You also have burning when you urinate, a cough with colored mucus, ear or sinus pain, or a rash
- You're pregnant
Get emergency help (call 911) if a fever comes with any of these:
- A stiff neck and a bad headache, or pain when bending your head forward
- Confusion, unusual drowsiness or a seizure
- Trouble breathing or chest pain
- A rash that doesn't fade when you press a glass against it
- Repeated vomiting, or you can't keep fluids down
- Severe pain anywhere
Frequently asked questions
Is 99.5°F a fever?
Not usually. Most doctors count 100.4°F (38°C) or higher as a fever in adults.
Can I take acetaminophen and ibuprofen together?
They are different medicines, and some doctors suggest alternating them, but it's easy to lose track of doses. Ask your doctor or pharmacist before combining them, and never go over either label's daily maximum.