It’s relatively common knowledge that the normal body temperature is 98.6° F (37° C), but your core body temperature actually varies by a degree or so throughout the day. For instance, your body temperature will be slightly lower in the morning and higher in the late afternoon into the evening. However, certain factors may cause your body temperature to dive below what’s considered normal or spike to pyrexia, more commonly known as a fever.
Unlike hypothermia, an emergency condition that develops when your body temperature reaches 95° F (35° C) or lower, a fever is fairly common and, in most cases, not very dangerous. Developing an elevated body temperature—whether it’s a high or low grade fever—is usually your body’s response to infection. Luckily, fevers typically last only a few days and there are several treatment options that can help you feel more comfortable.
What Is a Fever?
The normal human body temperature is 98.6° F (37° C), but other factors, including illness, certain medications, and specific medical conditions, can cause your temperature to rise. A fever is your body’s natural response to fighting an infection.
Any temperature between 98.6-100.4° F (37-38° C) is considered a low-grade fever, while any temperature above 103° F (39.4° C) is considered a high-grade fever. Unlike a significantly lower-than-normal body temperature, having a higher temperature isn’t necessarily dangerous.
One factor that differentiates what is considered a low or high body temperature is age. For adults and children, 95.1-96.9° F (35-36° C) is low and 100.4-103° F (38-39.4° C) is high, but neither case is necessarily an emergency. However, if a baby less than three months old experiences a temperature in either range, it may indicate a serious infection that requires immediate medical care.
This easy-to-read chart shows what various body temperatures mean and when to seek care. The measurements in this chart were made by mouth with the thermometer under the tongue.
Fever in Children
When adults develop a fever, they usually feel uncomfortable, but there’s typically no cause for concern, although an exception to this rule arises when an adult is undergoing chemotherapy treatment or has any condition which impairs the body’s ability to fight infections. When infants, toddlers, and children develop fever symptoms, they are more likely to need medical care.
If your toddler or child has a fever, but is still responsive, eating, drinking fluids, and playing, there’s no cause for concern. However, if your infant, toddler, or child experiences the following, you should either call your doctor or seek immediate care:
- More Irritable than usual
- Vomiting repeatedly
- A fever lasting more than three days
- Appears listless and unresponsive
Complications in children
Although fevers in children are quite common, some children between the ages of six months and five years may experience complications, such as febrile seizures or convulsions. Luckily, most children who experience fever-induced convulsions suffer no lasting effects and are not thought to be at higher risk of developing seizures or epilepsy later in life.
If your child has a seizure resulting from a fever, do the following:
- Lay your child on the floor on his or her side or stomach
- Clear the vicinity of any sharp objects
- Loosen any tight clothing
- Do not try to stop the seizure yourself
- Hold your child in place to prevent injury
Signs and Symptoms of Fever
Fever symptoms generally cause discomfort because your body is working to fight off an infection.
When you develop pyrexia, the most common symptoms you might experience include sweats, shivers, and headaches. Other common fever symptoms include:
- Muscle aches
- Loss of appetite
What Causes a Fever?
Your body’s internal thermostat is controlled by a small area in your brain called the hypothalamus. When your hypothalamus sets your internal body temperature higher than usual, this results in a fever. Usually the hypothalamus will reset this internal thermostat to normal within a few days. Although infection (which can be caused by either bacteria or viruses) is more often than not the cause of your fever, other causes include:
- Heat exhaustion
- Inflammatory conditions, such as rheumatoid arthritis
- Malignant tumors
- Drugs for high blood pressure and/or seizures
- Specific immunizations, such as diphtheria, tetanus, and pneumococcal vaccines
Diagnosing a Fever
Unlike many other illnesses, diagnosing a fever is something you can do at home. You should only seek medical attention if your high fever lasts more than a few days or is accompanied by any concerning symptoms.
Taking a temperature
The most obvious indication of a fever is a body temperature that’s higher than normal. The best way to measure your temperature is to take it using a thermometer. There are several different types of thermometers, but the most popular is a digital one, which you can use orally, rectally or axillary (under your armpit). Regardless of which type of thermometer you use, always be sure that the batteries aren’t expired as that may skew the results.
Other types of thermometers include a tympanic thermometer, which measures the temperature inside of the ear by reading the infrared heat. Most pediatricians use this method to take babies’ temperature if they’re three months or older.
Here’s how to use a digital thermometer:
- Make sure your hands and the thermometer are clean.
- Do not eat or drink anything for at least five minutes before you take your temperature because the food/drink may skew the results.
- Place the thermometer tip under the tongue, into the anus (using a petroleum jelly), or into your armpit and wait about 40 seconds. Most thermometers will beep when they have an accurate reading.
- Remove the thermometer and clean it with soap and water or with alcohol. Afterwards, be sure to rinse it.
Treatments for Fever
If you have a low-grade fever (up to 100.4° F and 38° C ), the best treatment may be letting the fever run its course. Having a slightly elevated body temperature can help get rid of the illness-causing microbes that are responsible for your cold, flu, or other viral infection. In cases of a high fever, there are a number of actions you can take to help lower your body temperature.
How to break a fever
As previously mentioned, having a fever isn’t necessarily a bad thing. It’s a sign that your body is fighting off an infection. However, in some cases, breaking your fever, or reducing your body’s temperature, can be helpful in making you feel more comfortable. Some of the most common ways to break a fever include:
- Over-the-counter medications: There are a variety of over-the-counter medications, such as acetaminophen and ibuprofen, that can help break your fever. However, taking too much of these medications or using them regularly over a prolonged period of time can cause liver and kidney damage. Children should never take aspirin, as it can cause a potentially fatal disorder called Reye’s syndrome.
- Antibiotics or antivirals: Depending on what’s causing your fever, your doctor may prescribe an antibiotic for a bacterial infection and an antiviral for a viral infection. Taking either, as directed by your doctor, can help break your fever.
- Hydrate: Drink plenty of non-alcoholic or caffeinated fluids to counteract the dehydration associated with fever.
- Let your body rest: Getting ample rest and staying cool can also help lower your fever.
What to eat when you have a fever
While your body and immune system need nutrients to fight off infection, your illness may be accompanied by nausea or lack of appetite. In that case, do not force yourself to eat. In fact, you should only eat if you are able to keep down food and if you feel hungry. Although the best thing you can do for a fever is to drink plenty of fluids, eating chicken soup has proven helpful as well. Other helpful foods include:
- Greek yogurt: If you can tolerate dairy, greek yogurt is an excellent food to eat when you have a fever because it contains a lot of probiotics, which help your immune system.
- Coconut water: Coconut water is naturally rich in electrolytes and potassium.
- Fruits with vitamin C: Most fruits are at least 80% water, making them an excellent source of hydration. Fruits containing vitamin C, such as oranges, can also help improve your immune response.
- Protein-rich foods: Foods including beans, nuts, lean meat, and poultry are high in protein, which your immune system needs in order to produce antibodies and fight off an infection.
The most effective way to prevent a fever is to avoid contracting an infection. While that’s not always possible, you can take the following steps to minimize your exposure to germs and diseases:
- Wash your hands: Wash your hands often with an antibacterial soap for at least 20 seconds.
- Use hand sanitizer: If you’re traveling and water and soap aren’t immediately available to you, using a hand sanitizer with at least 60% alcohol will help kill any germs.
- Avoid touching your face: Even if you wash your hands or use hand sanitizer, you may still be at risk, so avoid touching your nose, eyes, and mouth to prevent contracting an infection.
When to See a Doctor
Just because you have a fever doesn’t mean you need to pay a visit to the doctor. However, if you have a fever of 103° F (39.4° C), you should call your doctor, especially if your fever is accompanied by any of the following:
- Severe headache
- Skin rash that worsens quickly
- Sensitivity to light
- Stiff neck and/or pain when you bend your head forward
- Mental confusion
- Consistent vomiting
- Difficult breathing and/or chest pain
- Abdominal pain and/or pain when urinating
- Convulsions and seizures
- Severe sore throat or difficulty swallowing
- You are undergoing chemotherapy or other treatments for cancer or have any underlying chronic condition which suppresses your immune system
How K Health Can Help
While most fevers you can handle at home, sometimes you may need to speak to a doctor to make sure nothing more serious is going on. Did you know you can get affordable primary care with the K Health app? Download K to check your symptoms, explore conditions and treatments, and if needed text with a doctor in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.