What is fever?

Fever (also called pyrexia) is defined as body temperature that is higher than normal for each individual. It generally indicates that there is an abnormal process going on within the body. The severity of a condition is not necessarily reflected by the degree of fever. For example, influenza may cause a fever of 104° F, while pneumonia may cause a very low-grade fever or no fever at all. Consult with your physician if you have any questions about whether a fever is significant.

Vital Signs

What are vital signs?

Vital signs are measurements of the body's most basic functions. The four main vital signs routinely monitored by medical professionals and healthcare providers include:

  • body temperature
  • pulse rate
  • respiration rate (rate of breathing)
  • blood pressure (Blood pressure is not considered a vital sign, but is often measured along with the vital signs.)

Vital signs are useful in detecting or monitoring medical problems. Vital signs can be measured in a medical setting, at home, at the site of a medical emergency, or elsewhere.

What is body temperature?

The normal body temperature of a person varies depending on gender, recent activity, food and fluid consumption, time of day, and, in women, the stage of the menstrual cycle. Normal body temperature can range from 97.8°F (or Fahrenheit, equivalent to 36.5° C, or Celsius) to 99° F (37.2° C). A person's body temperature can be taken in any of the following ways:

  • orally
    Temperature can be taken by mouth using either the classic glass thermometer or the more modern digital thermometers that use an electronic probe to measure body temperature.
  • rectally
    Temperatures taken rectally (using a glass or digital thermometer) tend to be 0.5 to 0.7° (Fahrenheit) higher than when taken by mouth.
  • axillary
    Temperatures can be taken under the arm using a glass or digital thermometer. Temperatures taken by this route tend to be 0.3 to 0.4° (Fahrenheit) lower than those temperatures taken by mouth.
  • by ear
    A special thermometer can quickly measure the temperature of the ear drum, which reflects the body's core temperature (the temperature of the internal organs).
  • by skin
    A special thermometer can quickly measure the temperature of the skin on the forehead.

Body temperature may be abnormal due to fever (high temperature) or hypothermia (low temperature). A fever is indicated when body temperature rises above 98.6° F orally or 99.8° F rectally, according to the American Medical Association. Hypothermia is defined as a drop in body temperature below 95° F.

About glass thermometers containing mercury:

According to the Environmental Protection Agency (EPA), mercury is a toxic substance that poses a threat to the health of humans, as well as to the environment. Because of the risk of breaking, glass thermometers containing mercury should be removed from use and disposed of properly in accordance with local, state, and federal laws. Contact your local health department, waste disposal authority, or fire department for information on how to properly dispose of mercury thermometers.

What is the pulse rate?

The pulse rate is a measurement of the heart rate, or the number of times the heart beats per minute. As the heart pushes blood through the arteries, the arteries expand and contract with the flow of the blood. Taking a pulse not only measures the heart rate, but also can indicate:

  • heart rhythm
  • strength of the pulse

The normal pulse for healthy adults ranges from 60 to 100 beats per minute. The pulse rate may fluctuate and increase with exercise, illness, injury, and emotions. Girls ages 12 and older and women, in general, tend to have faster heart rates than do boys and men. Athletes, such as runners, who do a lot of cardiovascular conditioning, may have heart rates in the 40's and experience no problems.

Illustration demonstrating how to take a pulse

How to check your pulse:

As the heart forces blood through the arteries, you feel the beats by firmly pressing on the arteries, which are located close to the surface of the skin at certain points of the body. The pulse can be found on the side of the lower neck, on the inside of the elbow, or at the wrist. When taking your pulse:

  • Using the first and second fingertips, press firmly but gently on the arteries until you feel a pulse.
  • Begin counting the pulse when the clock's second hand is on the 12.
  • Count your pulse for 60 seconds (or for 15 seconds and then multiply by four to calculate beats per minute).
  • When counting, do not watch the clock continuously, but concentrate on the beats of the pulse.
  • If unsure about your results, ask another person to count for you.

If your physician has ordered you to check your own pulse and you are having difficulty finding it, consult your physician or nurse for additional instruction.

What is the respiration rate?

The respiration rate is the number of breaths a person takes per minute. The rate is usually measured when a person is at rest and simply involves counting the number of breaths for one minute by counting how many times the chest rises. Respiration rates may increase with fever, illness, and with other medical conditions. When checking respiration, it is important to also note whether a person has any difficulty breathing.

Normal respiration rates for an adult person at rest range from 15 to 20 breaths per minute. Respiration rates over 25 breaths per minute or under 12 breaths per minute (when at rest) may be considered abnormal.

What is blood pressure?

Blood pressure, measured with a blood pressure cuff and stethoscope by a nurse or other healthcare provider, is the force of the blood pushing against the artery walls. Each time the heart beats, it pumps blood into the arteries, resulting in the highest blood pressure as the heart contracts. One cannot take his own blood pressure unless an electronic blood pressure monitoring device is used. Electronic blood pressure monitors may also measure the heart rate, or pulse.

Two numbers are recorded when measuring blood pressure. The higher number, or systolic pressure, refers to the pressure inside the artery when the heart contracts and pumps blood through the body. The lower number, or diastolic pressure, refers to the pressure inside the artery when the heart is at rest and is filling with blood. Both the systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury). This recording represents how high the mercury column is raised by the pressure of the blood.

High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack). With high blood pressure, the arteries may have an increased resistance against the flow of blood, causing the heart to pump harder to circulate the blood.

According to the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), high blood pressure for adults is defined as:

  • 140 mm Hg or greater systolic pressure

    or 
  • 90 mm Hg or greater diastolic pressure

In an update of NHLBI guidelines for hypertension in 2003, a new blood pressure category was added called prehypertension:

  • 120 mm Hg - 139 mm Hg systolic pressure

    or
  • 80 mm Hg - 89 mm Hg diastolic pressure

The NHLBI guidelines now define normal blood pressure as follows:

  • Less than 120 mm Hg systolic pressure

    and
  • Less than 80 mm Hg diastolic pressure

These numbers should be used as a guide only. A single elevated blood pressure measurement is not necessarily an indication of a problem. Your physician will want to see multiple blood pressure measurements over several days or weeks before making a diagnosis of hypertension (high blood pressure) and initiating treatment. A person who normally runs a lower-than-usual blood pressure may be considered hypertensive with lower blood pressure measurements than 140/90.

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