When you have a fever, it’s understandable to worry about the cause. After all, it doesn’t feel good. Plus, if you have a fever, you probably don’t feel like doing much of anything else besides staying in bed and drinking plenty of liquids. You might even wake up at night sweating or shivering.
The first thing to understand is that most fevers are harmless. Many people get them every few years without any other symptoms for several days before they go away on their own.
In most cases, fevers rarely cause major problems. In fact, taking aspirin can make them go away faster. But if a fever lasts more than a day or two or causes symptoms such as vomiting and diarrhea, you need to see a doctor or go to an urgent care facility for fast treatment.
Other times when you should worry about your fever include:
1. When the fever remains high despite treatment at home
Parts of the body other than the head often run a few degrees higher than their normal temperature. If you have a fever but no other symptoms, you don’t need to worry about it. It will go away. But if your temperature is 101 or 102 degrees Fahrenheit (38 or 39 degrees Celsius) for more than 24 hours despite treatment at home, call your doctor. They may recommend taking aspirin every four hours until the fever goes down.
2. When you have a fever and other symptoms
Fevers cause most flu symptoms, including headaches, muscle aches, fatigue, chills, and dry coughs. These are the reasons many people think that they have influenza even if doctors can’t confirm it with laboratory tests. But sometimes people with fevers don’t feel ill, or they have other symptoms that indirectly point to the source of the high temperature—such as vomiting or diarrhea that could indicate food poisoning, strep throat, or abdominal inflammation.
3. When the fever is accompanied by pain
If your headache is severe enough to cause double vision or worse headaches, seek help quickly. The same holds true for high fevers caused by infections in bones or joints, especially if they last longer than five days without being treated.
4. When you have a fever in the late stages of pregnancy
It’s safe for most women to have low-grade fevers in later stages of pregnancy, but call your doctor if the fever is accompanied by other symptoms or goes up to 102 degrees Fahrenheit (38 degrees Celsius) or higher. Any fever when you’re in labor warrants calling your doctor for advice on how best to handle it.
- When you have a fever and a headache of unknown origin
The cause of your headache might be difficult to determine, but the doctor must find out why you have one. Headaches can signal severe meningitis, brain abscesses, or other conditions that need immediate treatment to prevent permanent damage. In some cases, headaches can also indicate more common ailments such as sinus infections or tension headaches.
- When you get a fever after being around someone who has meningitis
If you develop a fever after being with someone who has been diagnosed with meningitis—or possibly been exposed but not yet been diagnosed—you should seek medical care immediately in case you’re in the early stages of infection and need treatment, too.
- When you have a fever and experience memory loss
If you suddenly forget the name of your father-in-law or how to spell “Wisconsin,” seek help quickly. Up to 5 percent of people who have memory loss accompanied by a fever for more than a few hours may be experiencing early stages of dementia or Alzheimer’s disease.
- When you take medication that lowers your immune system (immunosuppressants)
Taking medications that suppress your immune system increases your risk of infections, whether they’re minor like strep throat or major like pneumonia. If you’re taking immunosuppressant drugs—such as those prescribed after an organ transplant—and you develop a fever, call your doctor immediately.
- When your temperature is 104 degrees Fahrenheit (40 degrees Celsius) or higher for a long time
When the fever lasts more than four days, call your doctor to see if you need medical tests to determine what’s causing it. If the cause isn’t found quickly, an infection could spread and do severe damage to vital organs such as the brain or heart. In rare cases, a high fever can also be caused by extremely high levels of steroid medication—for example, those used to treat people with rheumatoid arthritis or asthma who have been hospitalized because of problems with these diseases. A sudden increase in steroids may trigger fevers that continue without treatment for several days. This type of situation shows a spike in muscular weakness, dizziness or severe headaches, and severe nausea or diarrhea.
Sometimes you worry that a fever is a symptom of serious illness, but it’s not always the case. Knowing when to be concerned about your high temperature will help you understand what steps to take next. The signs and symptoms in this article should give you an idea of when it may be time for medical attention or if there are other factors at play, like medication use, that could contribute to the fever.