Fever & Temperature In Adults: When To Worry

Karen Justiniano, DO, MS, Stamford Health Medical Group

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A friend of mine whose father is 70 years old told me her story. It went something like this:

“My father never gets fevers. Out of nowhere the other day, he developed a 103 temperature with no other symptoms. He is also fully vaccinated against COVID-19. My mother brought him to the emergency room. Did she do the right thing, or would he likely have been fine if he stayed home and let the fever run its course?”

As a physician who cares for a variety of people with a variety of conditions, I have to say of course she did the right thing! When in doubt or when concerned, seeking medical attention is the smart thing to do.

But the longer answer is a little more complicated than that. It all starts with breaking down the purpose of a fever, and when you should truly worry. Please note—fevers in infants or young children are sometimes a different story—what you are about to read relates to adults only.

What is a fever and why do we get them, and sometimes with no other symptoms?

Fever is an elevated body temperature which means your temperature is 100.4 degree F or higher. A fever is the body’s way of fighting an infection by naturally raising your body’s temperature to “kill the germ.” The medical community likes to say that fever is a “good thing,” in most cases.

And yes, it’s completely possible for adults to develop a fever with no other symptoms, and for doctors to never truly find the cause. Viral Infections can commonly cause fevers, and such infections include COVID-19, cold or the flu, airway infection like bronchitis, or the classic stomach bug.

That’s why you often hear the word “viral” as an explanation because these types of infections often go away on their own after a few days.

What is considered a high fever in adults?

A high-grade fever in adults is 103 degrees F or higher.

Is it possible that a fever could be a sign of a “breakthrough case” of COVID-19 even if the person is fully vaccinated?

Yes, but not highly likely. Breakthrough cases of COVID-19 in fully vaccinated people have been reported, but symptoms tend to be milder than in non-vaccinated people, including fever.

First, make sure you are taking your temperature the right way. Taking your temperature by mouth is the most accurate method, and wait at least 30 minutes after you eat or drink anything hot or cold. Get medical attention for your fever if:

• Your temperature is high and has not gone down after taking Tylenol or Advil
• Your temperature lasts several days or keeps coming back
• You live in an area where people have COVID-19
• You have serious health conditions like diabetes, heart disease, cancer, lupus, or sickle cell anemia. (Non-infections like these can cause fever as well.)

You should also seek medial attention if you have a fever and you:

• Are pregnant
• Recently returned from travel overseas
• Get infections often
• Are on chemotherapy, in which case you should seek medical attention immediately if the fever lasts for more than one hour.
• Have recently been bitten by a tick

Is 98.6 still considered “normal” body temperature?

Yes and no. You’ve probably always heard that the average body temperature is 98.6, but the truth is there’s a much wider range—from about 97 to 99 degrees F.

So why is 98.6 suddenly a myth after all these centuries? Research suggests body temperatures are falling overall. Doctors have a few ideas about why this is, including lower metabolic rates, lower rates of infection and more advanced thermometers.

A couple of helpful reminders:

1. As the saying goes, “Don’t fear the fever.” A fever is your body’s first line of defense in fighting off an infection.
2. If you are not fully vaccinated against COVID-19, and have developed a high-grade fever, please call your doctor right away.

High Temperature Causes and Treatments

Written by Rick Ansorge

• What Is a Fever?
• Fever Symptoms
• Fever Causes
• Fever Diagnosis
• Fever Treatments

A fever is a body temperature that’s higher than is considered normal. It’s also called a high temperature, hyperthermia, or pyrexia, and it’s usually a sign that your body is working to keep you healthy from an infection. Normal body temperatures are different for everyone, but they lie within the range of 97 to 99. A temperature of 100.4 or higher is considered a fever.

A part of your brain called the hypothalamus controls your body temperature. In response to an infection, illness, or some other cause, the hypothalamus may reset the body to a higher temperature. So when a fever comes on, it’s a sign that something is going on in your body.

Fevers themselves generally aren’t dangerous, but you should check in with your doctor if:

• An adult’s temperature is 103 or higher
• A very young infant (under 3 months) has a rectal temperature 100.4 or higher (call your doctor or go to an emergency room immediately)
• A 3-6-month-old has a higher than normal rectal temperature and is also irritable or sleepy (call your doctor right away)
• A 3-6-month-old has a 102 or higher rectal temperature
• A 6-24-month-old has a fever higher than 102 for more than a day or with other symptoms such as a cough or diarrhea
• A child older than 2 has a fever that comes with rash, real discomfort, irritability, listlessness, headache, stiff neck, or repeated diarrhea or vomiting
• An infant or child has a seizure
• Any temperature over 104 in a child, which could cause a seizure
• Any fever that starts after someone has been in hot temperatures, which could be a sign of heat stroke
• The fever doesn’t go down after taking over-the-counter medications such as ibuprofen in the appropriate doses
• You’ve been in contact with someone who has COVID-19

Fevers are signs of some sort of illness or infection. When you have, you may also notice these symptoms:

• Chills or shivering
• Sweating
• Headache
• Feeling weak
• Being irritable
• Losing your appetite
• Being dehydrated

A fever can be a sign of several health conditions, which may or may not need medical treatment.

The most common causes of fever are infections such as colds and stomach bugs (gastroenteritis). Other causes include:

• Infections of the ear, lung, skin, throat, bladder, or kidney
• Heat exhaustion
• COVID-19
• Sunburn
• Conditions that cause inflammation, such as rheumatoid arthritis
• Side effects of medications
• Vaccines and immunizations
• Blood clots
• Autoimmune conditions such as lupus and inflammatory bowel disease (IBS)
• Cancer
• Hormone disorders such as hyperthyroidism
• Illegal drugs such as amphetamines and cocaine
• Teething in babies can cause a mild, low-grade fever (not over 101 degrees)

Although a fever is easy to measure with a thermometer, finding its cause can be hard. Besides a physical exam, your doctor will ask about symptoms and conditions, medications, and if you’ve recently traveled to areas with infections or have other infection risks. A malaria infection, for example, may cause a fever that typically comes back. Some areas of the U.S. are hot spots for infections such as Lyme disease and Rocky Mountain spotted fever.

Your doctor may ask if you have been around someone with COVID-19 or have any other symptoms of COVID-19.

Sometimes, you may have a “fever of unknown origin.” In such cases, the cause could be an unusual or not obvious condition such as a chronic infection, a connective tissue disorder, cancer, or another problem.

Fever is usually associated with physical discomfort, and most people feel better when a fever is treated. But depending on your age, physical condition, and the underlying cause of your fever, you may or may not require medical treatment for the fever alone. Many experts believe that fever is a natural bodily defense against infection. There are also many non-infectious causes of fever.

Treatments vary depending on the cause of the fever. For example, antibiotics would be used for a bacterial infection such as strep throat.

The most common treatments for fever include over-the-counter drugs such as acetaminophen and nonsteroidal anti-inflammatory drugs such as ibuprofen and naproxen. Children and teens should not take aspirin because it’s linked to a condition called Reye’s syndrome.

Stay comfortable by: 

• Drinking a lot of clear liquids such as water, broth, and juices or a rehydration drink.
• Taking a lukewarm bath.
• Resting.
• Keeping yourself cool with lightweight clothing and bed coverings.

Top Picks

Fever – Humanitas

Fever is usually a signal that something is wrong in the body. In an adult, fever is accompanied by malaise, however, as a rule, a temperature increase of no more than 103 F (39.4 C) is considered harmless. In children of the first days of life and infants, even a slight increase in temperature may indicate the presence of a serious infection.

However, the severity of the fever does not always indicate the severity of the underlying condition. A mild illness may cause a fever with a significant increase in temperature, and a severe illness may be accompanied by a slight increase in temperature.

The fever usually resolves within a few days. A number of over-the-counter drugs can lower a fever, but in some cases it is better not to lower it. An increase in body temperature greatly contributes to the body’s fight against a number of infectious diseases.

Symptoms

Fever is an increase in temperature above normal values. The temperature normal for an individual may be slightly above or below the average normal temperature 98. 6 F (37 C).

Fever, depending on the cause, may be accompanied by signs and symptoms such as:

• Sweating
• Trembling
• Headache
• Muscle pain
• Loss of appetite
• Dehydration
• General weakness

Fever 103 F (39.4 C) to 106 F (41.1 C) may cause:

• Hallucinations
• Confusion
• Irritability
• Convulsions
• Dehydration

Conditions requiring medical attention

Fever in itself is not a cause for concern and a reason to seek medical attention. However, there are times when, if you have a fever, you need to see a doctor yourself or take your child to the doctor.

Temperature measurement

Several types of thermometers are suitable for taking your own and your baby’s temperature, including oral, rectal, and ear (tympanic) thermometers.

Although not the most accurate method, an oral thermometer can be used to measure armpit temperature (axillary temperature).

• Place the thermometer in the armpit and cross your arms over your chest.
• Wait four or five minutes. Axillary temperature is slightly lower than oral.
• The doctor who came on call must be informed of the actual readings of the thermometer and name the place where the temperature was taken.

A rectal thermometer is suitable for measuring temperature in young children:

• To do this, grease the bulb of the thermometer with petroleum jelly.
• Place the baby on the stomach.
• Carefully insert the bulb of the thermometer half a centimeter into the child’s rectum.
• Hold the thermometer and child still for three minutes.
• Never let go of the thermometer while it is in the child’s body. If the child wriggles, the thermometer may go deeper and cause damage.

Infants

Unlike adults, unexplained fever in children is a serious cause for concern. If your child’s temperature rises to 101 F (38. 3 C) or more, contact your pediatrician. You should also call a doctor in the following cases:

• Fever in a child under 3 months old.
• Refusal of the child to eat and drink.
• Fever and unexplained irritability: the child cries a lot, for example when changing a diaper or at the slightest movement.
• Lethargy and lack of reaction in a child with fever. In infants and children under 2 years of age, these signs may be signs of meningitis, an infection and inflammation of the membranes and fluid surrounding the brain and spinal cord. If meningitis is suspected, the child should be seen by a doctor immediately.
• The body temperature of the newborn is below normal – below 97 F (36.1 C). In the youngest children, during illness, body temperature is difficult to regulate: it may fall rather than rise.

Children

If a child has a fever, but still reacts to others: makes eye contact, responds to facial expressions and voice, then there is probably nothing to worry about.

In the following cases, the child should be taken to the doctor:

• Lethargy or irritability, frequent vomiting, severe headaches or abdominal pain, or any other symptoms that cause severe discomfort.
• Fever after being in a hot car. Seek immediate medical attention if:
• Fever persists for more than one day (in children under 2 years of age) or more than three days (in children 2 years of age and older)

In special cases, for example, if the child has diseases associated with disorders of the immune system or any pre-existing diseases. Doctors also advise caution if a child has recently been prescribed a new drug.

Adults

Seek medical attention if:

• Temperature rises above 103 F (39.4 C)
• Persistence of fever for more than three days

In addition, seek immediate medical attention if any of the following signs or symptoms accompany a fever:

• Severe headache
• Severe swelling of the throat
• Unusual skin rash, especially if it progresses rapidly
• Unusual sensitivity to bright light
• Stiff neck and pain when bending head forward
• Confusion
• Prolonged vomiting
• Labored breathing or chest pain
• Extreme lethargy or excitability
• Abdominal pain or pain when urinating
• Other unexplained signs and symptoms

Complications

Fever may be accompanied by the following complications:

• Severe dehydration
• Hallucinations
• Fever-induced convulsions (febrile convulsions) in a small number of children aged 6 months to 5 years
• Febrile convulsions

Febrile seizures are usually accompanied by loss of consciousness and convulsions of the limbs, involving muscle groups on both sides of the body. Although febrile seizures are a cause of concern for parents, in most cases they do not have any long-term consequences.

If ​​a febrile seizure occurs:

• Place the child on its side or stomach on the floor or other flat surface
• Remove all sharp objects within reach of the child
• Rid the child of tight clothing
• Hold the child to avoid injury.

Do not put anything in the child’s mouth or try to stop seizures
In most cases, seizures go away on their own. After the seizures stop, it is necessary to show the child to the doctor as soon as possible to determine the cause of the fever.

If convulsions persist for more than 10 minutes, seek emergency medical attention.

high temperature, what to do?

High temperature is an increase in body temperature above normal values. Normal body temperature in the armpit is 36.0-36.9ºС, and in the morning it is 0.3-0.5ºС lower than in the evening. In the oral cavity and rectum, the temperature is usually 0.5-1 ºС higher than in the armpit, but does not exceed 37.5 ºС.

The causes of fever are manifold. The most common of these are infectious diseases. Microorganisms, their toxins and waste products affect the thermoregulatory center in the brain, causing an increase in body temperature.

There are several types of fever. According to the degree of temperature rise, subfebrile is distinguished – not higher than 37.5ºС; and febrile fever. Everyone is familiar with the manifestations of fever: muscle aches, headache, pain in the eyes, weakness, chills. Chills are nothing more than a physiological way to increase body temperature. When muscles contract, they increase heat production, and body temperature rises.

An increase in body temperature during an infectious disease does not occur by chance. Fever has important physiological significance. First, many bacteria die at high temperatures or lose their ability to reproduce. In addition, with an increase in body temperature, the body’s defense mechanisms to fight infection increase. Therefore, if the fever is benign and there are no other symptoms, drug treatment is usually not required – plentiful warm drinking and rest are recommended.

However, there are negative consequences of fever. In addition to subjectively unpleasant sensations, fever leads to increased fluid loss and excessive energy expenditure, which can be dangerous in people suffering from cardiovascular and other chronic diseases. High fever is especially dangerous for children who have an increased tendency to convulsions.

When should the temperature be lowered?

• For severe discomfort.
• Sleep disorders.
• When the temperature rises above 38.5°C.

Tips for lowering the temperature:

The room should not be too hot and should be ventilated regularly. Do not rub the patient’s skin with alcohol – this can increase the chills.