100, 101 or 102 Degree Fever? Adult Guide to High Temperatures

A fever is defined as a body temperature above 100.4°F (38.3°C).  The normal oral temperature for a resting, healthy adult is about 98.6°F (37°C). However, what is considered a “normal” body temperature can vary by one degree based on age, race, and other factors.  For example,  an individual who is over 70 years old may have a lower normal temp at 96.8°F (36°C). Furthermore, a person’s temperature may increase or decrease by 1 to 2 degrees throughout the day depending on time of day, activity level, the environment (hot or cold), hydration status, or even medications that he/she may be taking.

In general, a fever indicates the presence of inflammation.  It may occur in the presence of an underlying illness such as an infection, malignancy, or even bodily injury.  It may also be associated with certain autoimmune diseases.  Less commonly, certain medications are associated with fevers.  A fever itself, however, is merely a symptom, and not a disease.

A brain structure called the hypothalamus sets body temperature, and produces a fever response.  It can raise the body’s internal thermostat to combat illnesses.  In this way, the hypothalamus responds to an infection or inflammation by helping the immune system to defeat the offending agent.  Although it may not be comfortable, a temperature of up to 102°F is generally safe in adults. In fact, most healthy adults can even tolerate a fever as high as 103°F to 104°F for short periods of time without having any significant problems.  The body temperature usually returns to normal once the illness resolves.  Click here for a list of fever symptoms in adults.

Page Contents

What is the difference Between Fever and Hyperthermia?Ranges in Body TemperaturesSymptoms of FeverHow to Take Your Temperature – Fever in AdultsHow to Take Your Temperature – Fever in ChildrenHow to Take Your Temperature – ThermometersMercury ThermometerDigital ThermometersFever in adults – How to Treat a FeverWhen to Call Your DoctorTreatment of Hyperthermia Fever in Newborns and Children

What is the difference Between Fever and Hyperthermia?

The terms fever and hyperthermia are commonly confused, and are completely different entities. Hyperthermia is defined as a sustained body temperature above 104°F (40°C), and is just another word for overheating.   The hypothalamus functions normally, but the body’s ability to get rid of heat is impaired.  This most commonly occurs during exposure to extreme heat such as when exercising in hot outdoor temperatures.   Insufficient hydration can also increase the risk of hyperthermia.  

Ranges in Body Temperatures

While there are numerous definitions of fever or pyrexia, the CDC defines a fever as a temperature above 100.4°F (38°C). However, it is important to keep in mind that, in the elderly, temperatures below 100.4 may also be indicative of a fever.  The hypothalamus of these individuals is less able to elevate their body temperatures.  It is, therefore, important to take note of any additional concerning symptoms.

Here are some other definitions related to body temperature: 

• Normal: temperatures between 97.7°F (36.5°C) and 99°F (37. 2°C)
• Low-grade fever: temperatures between 99°F (37.2°C) and 100.4°F (38°C)
• Fever (pyrexia): temperatures between 100.4°F (38°C) and 105.8°F (41°C)
• Hyperpyrexia: temperatures between 105.8°F (41°C) and 109.4°F (43°C)
• Temperatures above 109.4°F (43°C) are usually fatal

Symptoms of Fever

Fevers can cause a wide variety symptoms. The most common ones are listed below:

1. 1. Muscle aches
   2. Headaches
   3. Irritability
   4. Chills
   5. Loss of appetite
   6. Sweating
   7. Generalized weakness

Click here for a list of fever symptoms in adults.

How to Take Your Temperature – Fever in Adults

Adults should use a digital thermometer, placing the tip under the tongue.  Forehead (temporal artery) measurements are also fairly accurate.  Readings taken with an ear (tympanic membrane) thermometer can vary, and may be inaccurate if there is an ear infection.  When readings from both ears are compared, the numbers may differ.

Taking a temperature under the armpit is not very accurate, but can be a quick way to take one’s temperature. When doing so, add one degree to know the true core body temperature.

How to Take Your Temperature – Fever in Children

When taking a child’s temperature, the digital thermometer tip should be placed under the tongue if age four or older. Tympanic membrane and forehead models may be used over the age of six months, but expect some variation in readings when using ear thermometers. 

In infants, the most accurate way to take a temperature is rectally.  A fever in infants under age three months can be a sign of a life threatening infection, so taking the temperature correctly is crucial.   

How to Take Your Temperature – Thermometers

Wash your hands with soap and warm water prior to using any thermometer. 

Mercury Thermometer

Because digital thermometers have become very affordable, the use of old glass mercury thermometers should be avoided.

Mercury is poisonous and is released when a glass thermometer breaks.  Furthermore, because it takes some skill to get a proper temperature reading, so they are not as accurate as the latest digital thermometers.

What to Do if a Mercury Thermometer Breaks.

Digital Thermometers

Digital thermometers are affordable, and readily available nowadays.  Because of the digital number displays, they are easy to read.  Click here for thermometer recommendations.

Before each use, make sure that the thermometer is clean and turned on. Again, wash your hands with soap and warm water to prevent the spread of infection. Follow the manufacturer’s instructions regarding appropriate usage for an accurate temperature reading, and always clean the thermometer before putting it away.

Fever in adults – How to Treat a Fever

• Stay hydrated.  In response to a fever, the body sweats in an effort to cool off.  Since sweat contains water, it must be replaced.  Water is the best option for rehydration in most cases.  If there are fluid losses due to vomiting or diarrhea, electrolyte replacement beverages may be ideal.
• Regularly take and record your temperatures.  If taking medication to lower the fever, it should drop within an hour.
• Monitor associated symptoms.  Take your temperature more frequently if your symptoms change (e.g. if you start vomiting)
• Antipyretics.  For fevers that are uncomfortable (e.g. associated muscle aches, headaches) you can take acetaminophen or ibuprofen. These medications help to reset your body’s thermostat, and lower the temperature.
• Do not give aspirin or products that contain it to children or teens under the age of 20. This can potentially cause Reye syndrome, a potentially dangerous condition
• Watch for signs of dehydration.  This can occur if the fever causes you to sweat excessively, or is associated with vomiting or diarrhea.  Signs of dehydration include thirst, dry skin, dry mouth, chills, feeling tired or weak, and dark-colored urine.
• Other fever remedies for adults.

When to Call Your Doctor

• Fevers above 103°F 
• Persistent fever.  Many viral illnesses, especially the flu, cause fevers of 102°F or higher for three to four days.  If associated with such illnesses, it is worth seeing a doctor for any fever that lasts longer.  For fevers that develop with no other symptoms, one should see a doctor if it lasts more than 48 hours.
• If your fever is associated with: 
  • Shortness of breath, chest pain 
  • Severe cough 
  • Seizures 
  • Confusion 
  • Persistent vomiting or diarrhea 
  • Severe headache 
  • Skin rash
  • Sensitivity to bright light and/or neck stiffness (could indicate meningitis – an infection of the lining of the brain, spinal cord)
  • Severe abdominal pain (could indicate diverticulitis, appendicitis, or other abdominal disorder)
  • Pain with urination (could indicate a urinary tract infection)

Treatment of Hyperthermia 

Hyperthermia is different from just a fever.   It is more dangerous.  The body becomes overheated and loses its ability to thermoregulate.  If measures are not taken to cool down the body, it can lead to organ damage and death.  When the body’s temperature rises above 104°F and is associated with other symptoms, it is called heatstroke.  This is a medical emergency and should be treated as such. Call 911. Symptoms may include:

• Confusion 
• Vomiting 
• Slurred speech
• Racing heart
• Rapid breathing 
• Loss of consciousness

Before these symptoms occur, moving indoors to an air-conditioned room can gradually lower the core body temperature to a safe range.  Drinking plenty of cool fluids is also helpful.

Fever in Newborns and Children

Fevers in newborns and children are often treated differently than those seen in adults. Please refer to the following links:

Fever in newborns can be serious, and should not be ignored.

Fever in Young Children (Toddlers) 

Remedies for fever in children

Note that the information in this article is purely informative and should never be used in place of the advice of your treating physicians.

When to Seek Care for a Fever

A fever (defined as a temperature of 100.4°F or higher) happens when your body is trying to fight off an infection or your immune system becomes activated. The increase in your body temperature signals that something is not quite right with you.

Sometimes a fever comes and goes quickly, other times it lingers, and your temperature fluctuates over time.

Below is a breakdown of when you should contact your doctor or health care provider if you have a fever:

Adults

Numbers that are cause for concern:

• 105°F – Go to the emergency room
• 103°F or higher – Contact your health care provider
• 101°F or higher – If you’re immunocompromised or over 65 years of age, and are concerned that you’ve been exposed to COVID-19, contact your health care provider

Situations that are cause for concern:

• if you have a fever and it doesn’t go down after taking over-the-counter medications, like ibuprofen
• if you’ve been in hot temperatures and develop a fever, it could be a sign of a heat stroke
• if you’ve been in contact with someone who tested positive for COVID-19, you could be at risk for the virus

Call your doctor for medical advice if you experience any of these situations.

Children

Call your child’s pediatrician under the following circumstances:

• 0-3 months – Your child has a temperature of 100.4°F or higher, with or without symptoms
• 3-6 months – Your child has a temperature of 100.4°F or higher, plus irritable behavior/sleepiness OR a temperature of 102°F or higher
• 6-24-months – Your child has a temperature of 102°F for longer than a day AND symptoms such as a rash, cough or diarrhea
• 2+ years – Your child has a temperature of 100.4°F or higher AND symptoms such as a rash, fatigue, headache, stiff neck, prolonged diarrhea or vomiting

Any age:

• Your child has a seizure
• Your child has a temperature of 103°F or higher
• Any fever that starts after your child has been in hot temperatures (could be a sign of heat stroke)
• Your child’s fever doesn’t go down after taking over-the-counter medications, like ibuprofen
• Your child has been in contact with someone who has COVID-19

Next Steps & Resources: 

• To make an appointment with a doctor near you, call 800-822-8905 or visit our physician directory to make an appointment online.
• Register for telemedicine through HMH Care NOW.

The material provided through HealthU is intended to be used as general information only and should not replace the advice of your physician. Always consult your physician for individual care

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.

How to take temperature with Apple Watch Series 8 and Apple Watch Ultra

At the launch of the new Apple Watch Series 8 and Apple Watch Ultra models, it was announced that they are equipped with a thermometer and can read body temperature readings from the wrist . However, later it was clarified that these data can only be used to obtain data on women’s health. At this point, a fairly large number of male users were simply discouraged. If you take the Apple Watch Series 8 and Apple Watch Series 7 models, then between them this is, in fact, the only difference that could push you to buy a new watch.

I would like to see an application for measuring temperature in future versions of watchOS.

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But the first buyers found a way out of the situation. Of course, it will not allow you to simply open the application and see your temperature, as you can do with an ECG or a pulse oximeter. But a certain idea will allow. In the Health app on the iPhone , you can activate the reading of the temperature from the wrist during sleep and see the deviation from the base values. Moreover, this option works regardless of the gender of the user. Let’s figure out how to set up Reading body temperature during sleep .

Apple Watch – temperature

Apple Watch Series 8 and Apple Watch Ultra received not just a thermometer on the inside, but two such sensors at once. One is located just on the inside, where all the other sensors are responsible for measuring pulse and blood oxygen saturation, and the second is right under the screen. This was done specifically in order to improve the accuracy of the data obtained by adjusting for the ambient temperature.

The ability to constantly record body temperature would be useful Apple Watch Ultra. Yet they are positioned as a gadget for extreme sports.

While you sleep, these sensors can measure your wrist temperature every five seconds and display fluctuations from a baseline. Therefore, from the very first night, the watch will not be able to show your temperature. You will have to sleep on the Apple Watch for several days before that, so that they first calculate the base temperature and only then show the nightly fluctuations. The graph that you can see will show more or less than the standard value was your temperature at night.

Based on the deviation that has appeared, it is possible to draw a conclusion about the current state of your health. After all, if the temperature is higher than the baseline, then there is a reason to think that something is not right with you, and measure it with a regular thermometer or consult a doctor. Such difficulties in measuring are due to the fact that the watch is constantly worn on the wrist. And getting the most accurate body temperature from there is quite difficult. Do you remember where it is best to measure the temperature?

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So, you can’t place a clock there. This is likely why Apple hasn’t provided users with a separate thermometer app. Otherwise, the number of self-diagnosed diagnoses that would not correspond to the actual body temperature could cause both a storm of indignation on the part of users and reputational losses.

How to measure temperature – Apple Watch

In some situations, it is important to determine body temperature in extreme conditions. For example, to avoid hypothermia.

In order for an Apple Watch Series 8 or Apple Watch Ultra to be able to track wrist temperature at night , several conditions must be met:

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In order for the watch to start measuring, you must allow it to record your sleep for five consecutive nights. After that, they will determine the base temperature of the wrist and display the deviation from it on the graph. But just like that, the measurements will not start. You need to activate them in the watch settings. To do this, do the following:

Wrist temperature measurement is enabled in the settings with one switch.

• On the iPhone, launch the Watch app and open your watch settings.
• Go to the “Privacy” section.
• Activate the Wrist Temperature switch.

To view your temperature data, you need:

Entering data into this section manually will not work.

• Open Health App .
• Go to the Overview tab.
• Select “Body measurements”.
• Open the “Wrist temperature” graph.

As you can see, this is the only temperature-related section that cannot be entered manually. Everything is calculated and filled only on the basis of Apple Watch data. Therefore, if you have an old clock and you just want to fill it yourself, then, unfortunately, this is not possible.

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Even in the description of this feature, Apple emphasizes that measurements are taken using Apple Watch:

Wrist temperature is a measurement of your local body temperature while you sleep using your Apple Watch.