How to Read a Glass Thermometer To Check Body Temperature

Reading a thermometer

Daniel Fahrenheit invented the glass thermometer, which contains mercury, to measure body temperature. On one end of the thermometer there is a silver colored bulb containing the mercury. When the mercury is warmed by body heat, it rises in a tube within the glass thermometer. To learn how to read a glass thermometer, check the steps below.

Instructions

1. Remove the thermometer from the patient after the allotted time.

2. 

   Using your thumb, index finger, and middle finger of your right hand, hold the thermometer from the non-mercury end (not by the silver tip) and lift the thermometer to a comfortable reading level.

3. 

   Slowly twist the thermometer until you can see the silver mercury inside the tube. The temperature scale in the form of hash marks will show along one side of the mercury and the numbers to tell you what the temperature is will display on the opposite side of the mercury. In the image to the left (click image to enlarge it), the green arrow is at 98.6 degrees, which is considered a normal temperature; and the red arrow is pointing to the end of the silver mercury. The patient's body temperature has warmed the mercury to this point.

4. To read the thermometer, look at the number on the far left as you hold the thermometer in your right hand. The number on the left is most likely a 94, indicating that if the mercury was at the hash mark over the number 94, then the patient's temperature is 94. Because of the smallness of the thermometer the number ' 9 ' is dropped from the gauge as your read right. Therefore, the number ' 6 'is for 96 degrees; the number ' 8 ' is for 98 degrees. The LONG hash marks between the numbers are for the in between numbers of 95 and 97. The SHORT hash marks are for tenths of degrees in even numbers (.2, .4, .6, .8).

5. Therefore, reading the thermometer from left to right, you would see 94 at a long hash mark, then four short hash marks, then a long hash mark for 95, then four short hash marks, then a long hash mark for 96, then four short hash marks, then a long hash mark for 97, and so on. Use the end of the mercury and the closest hash mark to determine the patient's temperature. From the Step 3 picture example, the mercury has risen to the 6th small hash mark past 100, meaning that the patient's temperature is 100.6 degrees.

Tips & Warnings

• If the thermometer reads less than 98 degrees and your patient is not suffering from hyperthermia, the thermometer may not have been properly inserted into the patient. Try taking the temperature again.

• Always sterilize the thermometer before and after the patient uses it. This can be accomplished with Isopropyl alcohol (rubbing alcohol) or sterile wipe.