In order to assist you with reading the patient's temperature, most thermometers have an arrow pointing to the line denoting the average normal body temperature (37º c or 98.6º f).

Figure. Reading a glass thermometer.

A Holding the thermometer.

B Rotating the thermometer.

C Reading the Fahrenheit thermometer.

D Same temperature on a Celsius thermometer.

B. Rotate the thermometer. The stem of the thermometer is not perfectly round. Its flattened areas act as a magnifying glass to make the hollow shaft in the stem appear larger. (The flattened areas also keep the thermometer from rolling off a flat surface.) Using your fingertips, slowly rotate the thermometer back and forth until the mercury in the shaft is clearly visible (see figure B). The column of mercury will appear to be silver in color and the rest (empty part) of the shaft will appear whitish. The column of mercury should be visible just above the numbers.

C. Locate the nearest temperature mark. There are several temperature markings (lines) on a thermometer. Identify the marking that is closest to the point where the mercury in the shaft stops (where the silver meets the white).

D. Determine the temperature reading. The method you use to determine the temperature reading of the mark you selected in the previous step depends upon whether you are using a Celsius thermometer or a Fahrenheit thermometer.

Fahrenheit thermometer. On a thermometer that uses the Fahrenheit temperature scale, each long mark shows a whole degree of temperature. There are four shorter lines between each pair of long lines. These shorter lines show an increase of two-tenths of a degree Fahrenheit (0.2ºF). For example, the first short mark past (to the right of) the 98ºF mark shows a temperature reading of 98.2ºF. The second mark shows a reading of 98.4º F. The third mark is 98.6ºF and the fourth is 98.8º F. The next mark is a long line and represents a reading of 99o F. In figure C, the temperature reading is 99.4º F.

Celsius thermometer. Like the Fahrenheit temperature, each long line on a thermometer using the Celsius scale denotes a whole degree of temperature. On the Celsius scale; however, there are nine shorter marks between each pair of long marks. Each small mark shows an increase of one-tenth of a degree Celsius (0.1º C). For example, the third short mark past the 38º C line denotes a temperature reading of 38.3ºC. Figure D shows the same temperature as figure C using a Celsius scale thermometer. The Celsius reading is 37.4º C.

Glass thermometers are designed so that the temperature reading will not go down (decrease) when the thermometer is removed from the patient. The temperature reading will remain unchanged unless the bulb end of the thermometer comes in contact with something hotter than the temperature reading shown on the thermometer or the thermometer is shaken down. "Shaking down" is the term given to the method of forcing mercury from the stem back into the bulb.

If a glass thermometer is not shaken down, then the thermometer continues to keep the same temperature reading. If it were to be used again on a second patient with a lower temperature, the thermometer would still show the temperature of the first patient.

H ow to “shake down” a glass thermometer:

Stand in a Clear Area. Stand in a clear area so that you will not hit the thermometer against anything during the shaking down process. Remember, the thermometer is glass and may shatter if it strikes anything hard like a table or bed frame.

Grasp the Stem End Securely. Grasp the end of the thermometer that is opposite the bulb end with your fingers and thumb. The stem ends in a knob (usually colored either blue or red) that helps you to hold onto the thermometer during the shaking down process.