What is body temperature?
Body temperature is a measure of the body’s ability to generate and get rid of heat. The body is very good at keeping its temperature within a narrow, safe range in spite of large variations in temperatures outside the body.
When you are too hot, the blood vessels in your skin expand (dilate) to carry the excess heat to your skin’s surface. You may begin to sweat, and as the sweat evaporates, it helps cool your body. When you are too cold, your blood vessels narrow (contract) so that blood flow to your skin is reduced to conserve body heat. You may start shivering, which is an involuntary, rapid contraction of the muscles. This extra muscle activity helps generate more heat. Under normal conditions, this keeps your body temperature within a narrow, safe range.
what is normal body temperature?
Temperature Of Healthy Human Body
Campbell, Neil A. Biology. 3rd ed. California: Benjamin Cummings, 1987: 790.
“… a human can maintain its ‘internal pond’ at a constant temperature of 37 °C”
“Temperature, Body.” World Book Encyclopedia. Chicago: Field Enterprises, 1996.
“… a healthy, resting adult human being is 98.6 °F (37.0 °C)”
Simmers, Louise. Diversified Health Occupations. 2nd ed. Canada: Delmar, 1988: 150-151.
“… the normal range for body temperature is 97 to 100 degrees fahrenheit or 36.1 to 37.8 degrees celsius”
Eisman, Louis. Biology and Human Progress. Englewood Cliffs, NJ: Prentice Hall, 1972: 125.
“… fairly constant temperature of 98.6 degrees”
McGovern, Celeste. “Snatched From an Icy Death.” Alberta Report/Western Report. Academic Abstracts: United Western Communications, 1994: 2.
“… core body temperature … the normal 37 °C”
Some studies have disputed Dr Wunderlich’s findings. For instance, a 1992 evaluation of his work in the US, and based on 148 participants, found that 36.8C was a more accurate figure.
Normal body temperature also depends on where the temperature reading is taken. For instance, a reading from the armpit will be about 0.5C lower than the body’s core temperature.
Research from Winthrop University in the US published in 2006 found that older people have lower temperatures and that, even when ill, their bodies may never reach temperatures that would be regarded as fever.
The NHS says that a normal temperature is around 37C (98.6F), although it depends on:
What they’ve been doing
The time of day
Which part of the body you take the temperature from
It is generally accepted that normal body temperature ranges between 36.1C (97F) to 37.2C (99F).
Where is body temperature measured?
Your body temperature can be measured in many locations on your body. The mouth, ear, armpit, and rectum are the most commonly used places. Temperature can also be measured on your forehead.
What are Fahrenheit and Celsius?
Themometers are calibrated in either degrees Fahrenheit (°F) or degrees Celsius (°C), depending on the custom of the region. Temperatures in the United States are often measured in degrees Fahrenheit, but the standard in most other countries is degrees Celsius.
What is normal body temperature?
Most people think of a “normal” body temperature as an oral temperature of 98.6°F (37°C). This is an average of normal body temperatures. Your temperature may actually be 1°F (0.6°C) or more above or below 98.6°F (37°C). Also, your normal body temperature changes by as much as 1°F (0.6°C) throughout the day, depending on how active you are and the time of day. Body temperature is very sensitive to hormone levels and may be higher or lower when a woman is ovulating or having her menstrual period.
A rectal or ear (tympanic membrane) temperature reading is slightly higher than an oral temperature reading. A temperature taken in the armpit is slightly lower than an oral temperature reading. The most accurate way to measure body temperature is to take a rectal temperature.
What is a fever?
In most adults, an oral temperature above 100°F (37.8°C) or a rectal or ear temperature above 101°F (38.3°C) is considered a fever. A child has a fever when his or her rectal temperature is 100.4°F (38°C) or higher.
What can cause a fever?
A fever may occur as a reaction to:
Infection. This is the most common cause of a fever. Infections may affect the whole body or a specific body part (localized infection).
Medicines, such as antibiotics, narcotics, barbiturates, antihistamines, and many others. These are called drug fevers, Some medicines, such as antibiotics, raise the body temperature directly. Other medicines interfere with the body’s ability to readjust its temperature when other factors cause the temperature to rise.
Severe trauma or injury, such as a heart attack, stroke, heat exhaustion or heatstroke, or burns.
Other medical conditions, such as arthritis, hyperthyrodism, and even some cancers, such as leukemia, hodgkin’s lymphoma, and liver and lung cancer.
Fevers are not to be confused with heat stroke. In fever the person can feel cold at high body temperatures since the body is fooled into thinking it is cold by the infectant microbe affecting the point that the body thermostat is set at. It is literally set higher than usual.
37°C (98.6°F) – Normal body temperature (which varies between about 36.123-37.5°C (96.8-99.5°F)
38°C (100.4°F) – Sweating, feeling very uncomfortable, slightly hungry.
39°C (102.2°F) (Pyrexia) – Severe sweating, flushed and very red. Fast heart rate and breathlessness. There may be exhaustion accompanying this. Children and epileptics may be very likely to get convulsions at this point.
40°C (104°F) – Fainting, dehydration, weakness, vomiting, headache and dizziness may occur as well as profuse sweating.
41°C (105.8°F) – (Medical emergency) – Fainting, vomiting, severe headache, dizziness, confusion, hallucinations, delirium and drowsiness can occur. There may also be palpitations and breathlessness.
42°C (107.6°F) – Subject may turn pale or remain flushed and red. They may become comatose, be in severe delirium, vomiting, and convulsions can occur. Blood pressure may be high or low and heart rate will be very fast.
43°C (109.4°F) – Normally death, or there may be serious brain damage, continuous convulsions and shock. Cardio-respiratory collapse will occur.
44°C (111.2°F) or more – Almost certainly death will occur; however, patients have been know to survive up to 46°C (114.8°F).
37°C (98.6°F) – Normal body temperature (which varies between about 36-37.5°C (96.8-99.5°F)
36°C (96.8°F) – Mild to moderate shivering (this drops this low during sleep). May be a normal body temperature.
35°C (95.0°F) – (Hypothermia) is less than 35°C (95.0°F) – Intense shivering, numbness and blueish/greyness of the skin. There is the possibility of heart irritability.
34°C (93.2°F) – Severe shivering, loss of movement of fingers, blueness and confusion. Some behavioural changes may take place.
33°C (91.4°F) – Moderate to severe confusion, sleepiness, depressed reflexes, progressive loss of shivering, slow heart beat, shallow breathing. Shivering may stop. Subject may be unresponsive to certain stimuli.
32°C (89.6°F) – (Medical emergency) Hallucinations, delirium, complete confusion, extreme sleepiness that is progressively becoming comatose. Shivering is absent (subject may even think they are hot). Reflex may be absent or very slight.
31°C (87.8°F) – Comatose, very rarely conscious. No or slight reflexes. Very shallow breathing and slow heart rate. Possibility of serious heart rhythm problems.
28°C (82.4°F) – Severe heart rhythm disturbances are likely and breathing may stop at any time. Patient may appear to be dead.
24-26°C (75.2-78.8°F) or less – Death usually occurs due to irregular heart beat or respiratory arrest; however, some patients have to been known to survive with body temperatures as low as
Symptoms of fever
The symptoms of fever can include:
- Feeling unwell
- Feeling hot and sweaty
- Chattering teeth
- Flushed face.
Infection is usually the cause of fever
The cause of fever is usually an infection of some kind. This could include:
- Viruses – such as colds or upper respiratory tract infections.
- Bacteria – such as tonsillitis, pneumonia or urinary tract infections.
- Some chronic illnesses – such as rheumatoid arthritis and ulcerative colitis that can cause fevers that last longer than two weeks.
- Some tropical diseases – such as malaria, which can cause bouts of recurring fever or typhoid fever.
- Heat stroke – which includes fever (without sweating) as one of its symptoms.
- Drugs – some people may be susceptible to fever as a side effect of particular drugs.
- Malignant tumours.
Self-treatment suggestions for fever
Suggestions to treat fever include:
- Take paracetamol or ibuprofen in appropriate doses to help bring your temperature down.
- Drink plenty of fluids, particularly water.
- Avoid alcohol, tea and coffee as these drinks can cause slight dehydration.
- Sponge exposed skin with tepid water. To boost the cooling effect of evaporation, you could try standing in front of a fan.
- Avoid taking cold baths or showers. Skin reacts to the cold by constricting its blood vessels, which will trap body heat. The cold may also cause shivering, which can generate more heat.
- Make sure you have plenty of rest, including bed rest.
When to see your doctor for fever symptoms
You should always consult with your doctor in the following cases:
- You are still feverish after three days, despite home treatment.
- Your temperature is over 40°C.
- You are shivering and shaking involuntarily, or your teeth are chattering.
- You are hot, but not sweating.
- You seem to be getting sicker as time goes by.
- You have unusual symptoms such as hallucinations, vomiting, neck stiffness, skin rash, rapid heart rate, chills or muscle spasms.
- You feel confused and drowsy.
- You have a severe headache that doesn’t respond to painkillers.
- You have recently travelled overseas.
When to seek immediate urgent medical attention
You should seek immediate medical attention if you or someone else has the following symptoms:
- Fever with headache and a stiff neck
- Rash that does not blanche to skin pressure (indicates bleeding into the skin) This can indicate a life threatening illness
Since fever is a symptom and not an illness, the underlying cause must be found before specific treatment can begin. Some tests may be necessary if the cause of the fever is not clear after your doctor has taken a medical history and performed an examination. These tests may include:
- Blood tests
- Urine examination and culture
- Throat swabs or mucus sample examination and culture
- Stool examination and culture
Treatment depends on the cause – for example, chronic tonsillitis may require surgery to remove the tonsils (tonsillectomy). Fevers caused by viral illnesses shouldn’t be treated with antibiotics, since these drugs have no effect against viruses. In cases of mild bacterial infection, it is usually best to allow your immune system to handle the problem, rather than take antibiotics.
Fever in children
On average, a child has up to 10 infections per year. Body temperature isn’t a reliable indicator of illness for babies and young children – a child may have a mild temperature according to the thermometer (slightly over 37°C), but seem happy and healthy. Trust your own instincts, but seek medical help if your child:
- Is aged six months or less
- Has a rash
- Has a fever of 40°C or more
- Is still feverish after a day or so, despite four-hourly doses of baby paracetamol
- Vomits or has persistent diarrhoea
- Refuses food or drink
- Cries inconsolably
- Seems listless, floppy or just looks ill
- Convulses or twitches
- Has trouble breathing
- Is in pain
- If you feel at all worried or concerned at any stage, consult with your doctor.
Where to get help
- Your doctor
- The Maternal and Child Health Line is available 24 hours a day Tel. 13 22 29.
- Nurse-on-Call Tel. 1300 60 60 24 – for expert health information and advice (24 hours, 7 days)
Things to remember
- Fever is a rise in body temperature, usually caused by infection.
- Fevers caused by viral illnesses shouldn’t be treated with antibiotics, since these drugs have no effect against viruses.
- High fever (about 41.5°C or more) is extremely dangerous and could trigger convulsions.