Application of Measurement and Dose Conversion
Upon completion of this chapter, the learner will be able to:
1. Define the key terms that relate to the chapter.
2. Identify common abbreviations used in the health care field.
3. Interpret basic physician’s orders.
4. Use the appropriate equivalents to solve conversion problems using the metric, apothecary, and U.S. Customary (household measurements) systems.
5. Convert temperature measurements between Fahrenheit and Celsius.
The measurement of temperature with 0 degrees representing the freezing point and 100 degrees representing the boiling point of water.
Weight of medication in a dose (mEq, mcg, mg, G).
The measurement of temperature with 32 degrees representing the freezing point and 212 degrees representing the boiling point of water.
The part of the prescription that identifies the medication and dosage.
Directions for administration of medication; these may be written or verbal orders.
The amount of medication that is to be dispensed.
The number of times the physician will allow the prescription to be repeated.
How the medication is to be given.
The part of the prescription that indicates the dosage and frequency with which the medication is to be given.
Objective 1
Have you ever read the label on a pill bottle after a prescription has been filled? Many times, you will see a mixture of metric and U.S. Customary (household) measurements (Figure 9-1). Then the pharmacist hands you a measuring device with both metric and U.S. Customary (household) measurements on it (Figure 9-2). You want to give or take the correct dose, but which do you use—milliliters or teaspoons?


In the previous chapters, all of the questions dealt with the same base measurements. In this chapter, however, we practice converting between metric, apothecary, and U.S. Customary (household) measurements. The chapter also discusses common abbreviations used in the health care field, interpretation of physician orders, and conversion of temperature measurements from Fahrenheit to Celsius.
Objective 2
Common abbreviations used in the health care field
Have you ever taken a foreign language class? Medical terms and abbreviations used in the health care field can be compared to a foreign language. Because the medical field has a Latin word base, translations may not be obvious.
Tables 9-1 and 9-2 identify common abbreviations that are used when giving orders in the health care field. It is important that all health care professionals understand and can interpret common abbreviations—these abbreviations are not exclusive to the study of pharmacology.
TABLE 9-1
Abbreviations Commonly Used by Pharmacology and Nursing Health Care Workers
Abbreviation | Meaning |
a.c. | Before meals |
Ad lib | As desired |
a.m. | Morning |
bid | Twice a day |
BP | Blood pressure |
c¯ | With |
d | Day |
d/c | Discontinue |
H, hr | Hour |
hs | Hour of sleep |
IM | Intramuscular |
IV | Intravenous |
K | Potassium |
Na | Sodium |
npo | Nothing by mouth |
pc | After meals |
p.m. | Afternoon |
PO | Per oral or by mouth |
prn | As needed |
Q, q | Every |
qid | Four times a day |
qs | Quantity sufficient |
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Prescription |
s¯ | Without |
SC, SQ, Subq | Subcutaneous |
Sig | Directions |
SL | Sublingual, under the tongue |
STAT | Immediately |
Tab | Tablet |
tid | Three times a day |
TPR | Temperature, pulse, respiration |
VO | Verbal order |
VS | Vital signs |
TABLE 9-2
Abbreviations Commonly Used by Laboratory and Nursing Health Care Workers
Abbreviation | Meaning |
BM | Bowel movement |
CBC | Complete blood count |
CMP | Comprehensive metabolic panel |
FBS | Fasting blood sugar |
Hct | Hematocrit |
Hgb | Hemoglobin |
H/H | Hemoglobin and hematocrit |
Plat. | Platelets |
WBC | White blood count |
The frequency of an order can be confusing. The abbreviation BID, which means “twice a day,” is not the same as q2h, which means “every 2 hours.” When requesting that a procedure, therapy, or medication be given at a specific time interval, the physician writes the hour frequency as a number.
Example:
Unasyn 500 mg IV
Q8H × 3 days
The above example Q8H means to give the medication every 8 hours. This order is more specific than tid (three times a day).
Objective 3
Interpretation of physician’s orders
Physician’s orders are given by the physician either in writing or orally to communicate what medication, tests (e.g., laboratory), or therapy he or she would like to have implemented. Orders are written in the patient’s chart by designated health care personnel. Medical abbreviations are commonly mixed in with longhand descriptions of the orders.
Example:
CBC q6h × 3 days then D/C.
Interpretation: Draw blood for a complete blood count every 6 hours for 3 days, then discontinue.
All physician’s orders should have the same basic information—what is to be done and how often.
Medication orders and prescriptions must include specific information (Figure 9-3):

1. Name of the medication | Inscription |
2. Dosage strength of the medication | Inscription |
3. How the medication should be taken | Route |
4. How often the medication should be taken | Frequency or Signa (Sig) |
5. How much medication should be dispensed | Quantity |
6. How many refills of the medication are allowed |
Let’s look at the prescription in Figure 9-3 and identify the required information.
1. Name of the medication | Pen-V-K (correct name: Pen-Vee K) |
2. Dosage strength of the medication | 250 mg |
3. How the medication should be taken | Tablets (by mouth) route |
4. How often the medication should be taken | Every 6 hours |
5. How much medication should be dispensed | 40 tablets |
6. How many refills of the medication are allowed | Refills are not specified so there would be no refills |
Depending on the medication orders written, math may be involved in determining the correct amount of medication to be dispensed, the way to reconstitute the medication, and the amount of medication to be given over a specified period of time.

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