Taking a Rectal Temperature

Medically reviewed by Drugs.com. Last updated on Feb 21, 2024.

What is it?

A rectal temperature (TEM-per-ah-chur) is a way of taking your child's temperature . Caregivers may want rectal temperatures taken on children less than 5 years old. A rectal temperature is taken by putting the thermometer (ther-MOM-uh-ter) gently in your child's rectum. The rectum is the end of the bowel. The opening into the rectum is called the anus. The anus is the hole in your child's bottom where a bowel movement (BM) is passed from the body. Make sure you follow directions for taking a rectal temperature very carefully .
Do not take a rectal temperature if your child has had surgery on his rectum, has any kind of rectal disorder, or if he bleeds easily.

Why do I need to check a rectal temperature?

The rectal temperature is the most exact way to know if your child has a fever. A temperature taken in the rectum is the closest way to finding the body's true temperature. Rectal temperatures run higher than those taken in the mouth or armpit (axilla) because the rectum is warmer. The normal rectal temperature of a child is between 97° and 100° F (36.0 to 37.7° C).

What kind of thermometer is used to take a rectal temperature?

A digital thermometer is used to take a rectal temperature. It is a small hand-held device with a "window" showing your child's temperature in numbers. There are many kinds of digital thermometers. Most digital thermometers are easy to use and measure body temperature in less than a minute. Carefully read the instructions before using your digital thermometer. Digital thermometers can be bought at grocery, drug or medical supply stores.
Glass thermometers with red or blue alcohol inside may be used to check a rectal temperature. Glass thermometers with galinstan (GAL-in-stan) may also be used to check a rectal temperature. Galinstan thermometers have a silver-colored tip and line, but will be marked "mercury-free" when you buy one. Be very careful to stay with your child while taking a rectal temperature with a glass thermometer. Infants and children may move suddenly and break the thermometer. You may need to hold the thermometer in place for three or more minutes in order to get a correct reading. Alcohol-filled and galinstan glass thermometers are harder to find in grocery stores than digital thermometers.
In the past, mercury (MER-kure-e) thermometers were used. This thermometer is a thin glass tube with a silver tip and line inside. The silver in the tip and line is mercury. Mercury is a toxic and hazardous chemical. The Environmental Protection Agency (EPA), the American Academy of Pediatrics (AAP), and other organizations warn against using mercury thermometers. If the thermometer breaks, the mercury may be breathed in or absorbed (soaked) into your skin. Mercury is bad for your health, as well as for the water, wildlife, and waste systems on earth.
If you have a mercury thermometer, replace it with a digital thermometer. You may also replace it with a glass thermometer having alcohol or galinstan instead of mercury. If your mercury thermometer breaks, do not touch the thermometer or the mercury. Do not try to clean up the spill. Open your window to air out the area. Take children and pets out of the area right away. Contact the following:

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How do I use a digital thermometer?

Take the thermometer out of its holder.
Clean the probe (pointed end) of the thermometer with rubbing alcohol or soap and then rinse it in cool water.
Slide a probe cover over the pointed end of the thermometer. If your thermometer did not come with a probe cover then you can use it without one.
Lubricate the end of the probe with a small amount of lubricating jelly.
Place your child on his stomach across a firm surface or your lap before taking his temperature.
Gently slide the probe of the thermometer into the rectum about a 1/2 inch. Stop inserting the thermometer if it becomes difficult to insert. Never force the thermometer into the rectum.
Continue to hold the thermometer the entire time you are taking the temperature. Always stay with your child while taking the temperature.
Keep the thermometer in place until it beeps.
Remove the thermometer.
Read the numbers in the window. These numbers are your child's temperature.
Your child's caregiver may want you to keep a temperature record. Write down the time and temperature each time you take it.
If you used a probe cover, remove it and throw it away.
Wash the probe of the thermometer with soap, water and rubbing alcohol when you are done.

How do I use a glass thermometer?

Take the thermometer out of its holder.
Clean the thermometer with rubbing alcohol or soap and then rinse it in cool water. Do not use hot water because it may break the thermometer.
Hold the thermometer by the end opposite the red, blue, or silver-colored bulb.
Shake the thermometer downward several times.
Turn the thermometer in your hand until you see the line. The line should read less than 96 degrees F (35.6 degrees C). If the mercury line reads more than 96 degrees F (35.6 degrees C), firmly shake the thermometer again. You may want to shake the thermometer over a couch or bed. This will keep it from breaking if it slips out of your hand.
Check the thermometer again to make sure it reads 96° F (35.6° C) or less.
Lubricate the bulb end with a small amount of lubricating jelly.
Place your child on his stomach across a firm surface or your lap before taking his temperature.
Gently spread the buttock cheeks and place the red, blue, or silver end into the rectum about 1 inch. Stop inserting the thermometer if it becomes difficult to insert. Never force the thermometer into the rectum.
Hold the thermometer between your second and third fingers with your hand cupped over your child's buttocks. Continue to hold the thermometer in place while taking his temperature. Always stay with your child while taking his temperature.
Keep the thermometer in place for 3 minutes.
Remove the thermometer without touching the bulb.
Hold the thermometer at eye level.
Slowly turn the thermometer until you see the end of the red, blue, or silver-colored line. Each long mark is the same as 1 degree. Short marks are the same as 0.2 degree.
Your child's caregiver may want you to keep a temperature record. Write down the time and temperature each time you take it.
Clean the thermometer with rubbing alcohol or soap and then rinse it with cool water. Do not use hot water because it may break the thermometer.

Care:

Keep the rectal thermometer clean. Wash it well with soap, water and rubbing alcohol after each use. Put the thermometer in a safe place until it is ready to be used again.

Care Agreement

You have the right to help plan your child's care. Learn about your child's health condition and how it may be treated. Discuss treatment options with your child's caregivers to decide what care you want for your child.

The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

Further information

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