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Healthcare Math:
Calculating Dosage
Industry: Healthcare
Content Area: Mathematics
Core Topics: Applying medical abbreviations to math problems, using formulas, solving algebraic
equations
Objective: Students will be able to accurately calculate the dosage of medication in the correct form
to fill a doctor’s prescription
Materials included:
Instructor’s notes
Scenario: Pharmacy Technician
Student worksheets
Handouts
Quiz
Answer Keys
Industry Overview:
According to the U.S. Department of Labor, the healthcare industry is expected to generate over 20%
of all new jobs created in the U.S. economy between 2012 and 2022.* The healthcare industry is
comprised of a vast array of jobs, ranging from nursing assistants to physicians. Mathematics and
literacy skills are essential for students who plan to pursue a career in this field. Healthcare
professionals, including pharmacy technicians, need to understand medical terms, abbreviations, and
metric measurements. They must also have the ability to use formulas to calculate the correct dosage
of medication for patients.
* Source: http://www.bls.gov/news.release/ecopro.t06.htm
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Instructor’s notes:
The purpose of this module is to help students develop and apply math skills in a healthcare
workplace setting. The learning activities were designed to be incorporated throughout
multiple instructional periods as math concepts are taught in a healthcare context.
After completing the module, students should be able to:
o Interpret the essential information contained on a prescription
o Apply medical abbreviations to solve mathematical problems
o Use a formula to calculate the correct dosage of medication to fill prescriptions
Setting the stage: Provide students with background information about the typical
responsibilities of a pharmacy technician. You may want to have students use the
occupational outlook handbook, O*NET and/or other relevant websites to research the job
responsibilities, educational/training requirements, salary, etc. for this position. In addition, you
could have students view YouTube videos depicting the typical responsibilities of a pharmacy
technician. (See links below)
Bureau of Labor Statistics – Occupational Outlook Handbook:
http://www.bls.gov/ooh/
Occupational Information Network (O*NET)
http://www.onetonline.org/link/summary/29-2052.00
Pharmacy Technician videos:
http://www.youtube.com/watch?v=DW81Hd2YENY
http://www.youtube.com/watch?v=E_cBkSiaQD8
For Activity 1: Prescription Abbreviations Have students work individually, or in pairs, to
review and study common prescription abbreviations listed in the scenario. You may want
students to make flash cards to quiz each other on the terms. Have students complete
Worksheet 1.
For Activity 2: Decoding Prescriptions As a class, review the sample prescription and
decode the information. Using copies of Worksheet 2, have students practice translating the
information on several prescriptions. Handouts 2A, 2B, & 2C have some sample
prescriptions, or you may want to use others of your own choosing.
For Activity 3: Calculating Dosage Explain the dosage formula to students. As a class,
practice putting the information into the formula and calculating the dosage. One example is
contained in the scenario. You may want to provide additional examples for students. Have
students complete Worksheet 3A and Worksheet 3B.
Assessment: Quiz - Calculating Dosage
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Workplace Scenario: Pharmacy Technician
Maria is a pharmacy technician at a local pharmacy. Working under the supervision of a pharmacist,
she fills a variety of prescriptions for customers each day. Currently, you are a pharmacy technician
student receiving on-the-job training from Maria.
Activity 1: Prescription Abbreviations
Maria tells you that filling prescriptions accurately is extremely important, even one small error could
cause great harm, or even death to a patient. The first step in filling any prescription is to understand
all the information contained on the prescription form, including the medical abbreviations. Maria
gives you the following chart to help you learn some common abbreviations used on prescriptions.
She then asks you to complete Worksheet 1.
Some common abbreviations found on prescriptions
Abbreviation
Meaning
ac
before meals
bid
twice a day
cap
capsule
d
day (24 hours)
Exlir.
liquid or syrup
g
gram – dry measure used in tablets
gr
grains – dry weight of medication
gt
drop
h
hour
hs
at bedtime
IM
Intramuscular
mg
milligram – dry weight measure
mL
milliliter – liquid volume measure
po
by mouth
pc
after meals
pil
pill
prn
as needed
q
every
q2h
every 2 hours
qd
every day
qh
every hour
Sig
patient instructions
qid
4 times a day
Supp.
medications inserted rectally
Ṫ
One tablet
tab
tablet
tid
3 times a day
U
Unit
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Worksheet 1: Prescription Abbreviations Name _________________________
Directions: Put the letter of the definition next to the correct medication abbreviation
1. qid _______
A. by mouth or orally
2. hs _______
B. liquid or syrup
3. bid _______
C. every day
4. g _______
D. three times a day
5. mg _______
E. medication inserted rectally
6. po _______
F. milligram
7. qd _______
G. four times a day
8. gr _______
H. every 6 hours
9. U _______
I. milliliters
10. tid _______
J. as needed
11. Elix. _______
K. grain
12. Supp. _______
L. Unit
13. q6h _______
M. at the hour of sleep; bedtime
14. mL _______
N. gram
15. prn _______
O. twice a day
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Activity 2: Decoding Prescriptions
Maria wants you to learn how to accurately interpret the information contained on a typical
prescription. This includes the name of the medication, the dosage and form of the medication, the
amount to be taken, the method of administration, and the frequency and duration the medication will
be taken. As a pharmacy technician, you need to read the prescription very carefully. Many
medications have similar names or come in more than one form. For example, an older adult may
take the capsule or tablet form of a medication, while a young child might be prescribed an elixir, the
liquid form of a medication. She gives you the following sample prescription and asks, “How would
you translate this information?”
Maria explains:
The first part of a prescription is the name of the drug; it can be a brand name or generic. On this
In this case, it's 250 milligrams in the form of tablets. “ṪṪ” stands for two tablets. The “po” means the
medication is taken by mouth “tid” or three times a day. The ‘x’ indicates this prescription is to be
taken for a period of 7 days. Two tablets x 3 times a day for 7 days = 42, the total number of tablets to
be dispensed.
Maria gives you several prescriptions and asks you to complete all the information on Worksheet 2
for each prescription.
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Worksheet 2: Decoding Prescriptions Name: _______________________
Directions: On your own paper, record the following information for each prescription your instructor
gives you.
The patient’s full name
The date
The drug name in manufacturer or generic
format
The doctor’s order for dosage amount (how
much medication)
The administration route (by mouth, IV,
injection)
The frequency with which the patient is to
take the medication
The duration, the number of days that the
patient is to take the medication
The total quantity or amount that the
pharmacist is to dispense
A check-off or box allowing a generic
substitute (if provided)
The physician’s name
The physician’s DEA number
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Handout 2A: Sample Prescriptions
Phone 123-456-7890 DEA# 012345678
Patty Street, MD
Pediatrician
Pt. name Tim Jones Age 10 Date Aug. 30,
2014
Address: 2 Joyce Road, Anyway, IL 62000
R
X
Ceclor 10 mL bid x 10 d
Refill: 0 X Generic and/or equivalent allowed
Physician’s Signature PStreet
Pediatric Center
123 Abbey Road
Anyway, IL 62000
Phone 123-456-7890 DEA# 012345678
Sarah Jean, MD
Pt. name Mary Brown Age 47 Date Sept. 20, 2014
Address: 789 6th Street,
R
X
Darvon 1 g tab. p.o. q4h for 3 days
Refill Ø__ Generic and/or equivalent allowed
Physician’s Signature S Jean
SJMedical Associates
23South Street
Anytown, IL 62222
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Handout 2B: Sample Prescriptions
Phone 123-456-7890 DEA# 012345678
Sarah James, MD
Pt. name Jeff Howard Age 53 Date Sept. 20, 2014
Address: 1234 5th Street,
R
X
Ampicillin 250mg po qid x 10 days
Refill Ø__ Generic and/or equivalent allowed
Physician’s Signature S James
SJMedical Associates
23South Street
Anytown, IL 62222
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Handout 2C: Sample Prescriptions
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Activity 3: Calculating Dosage
Maria says you are now ready to learn the dosage formula used to calculate the amount of
medication needed to fill a prescription.
Dosage Formula:
Doctor’s Order (D) x quantity(Q) = individual dosage to be administered
Supply on Hand (H)
Short version: D x Q = one dose
H
The formula can be read as: The doctor’s order (the numerator) divided by the supply on hand (the
denominator), multiplied by the quantity equals the amount of one dose of medication.
Understanding the parts of the Dosage Formula
Doctor’s Order (D) is the name and amount of the medicine prescribed by the doctor
Supply on Hand (H) is the amount per item of the medication that is available in the pharmacy
Quantity (Q) is the form of the medication, such as tablet, capsule, or milliliter.
Dosage is the amount of medication to be given in one dose
Important: The doctor’s order and the supply on hand must be in the same unit of measure, such as
grams (g), milligrams (mg), and milliliters (mL). Answers must include the correct unit notation.
Maria gives you the following example: Dr. Smith has prescribed 30 mg of medicine for her patient.
The drug label on the medicine indicates that the medicine is supplied in 60 mg per tablet. We will
use the dosage formula to calculate the correct amount of medication for one dose.
(D) 30 mg x (Q) 1 tablet = 0.5 mg. Therefore, one dose will be one half (1/2) tablet
(H) 60 mg
Important: In the medical field, any decimal number that is not greater than 1 should have a 0 in
front of the decimal point. Thus, the correct form for the dosage in this example is 0.5 mg, not .5 mg
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Worksheet 3A: Calculating Dosage Name________________________
Maria gives you several prescriptions for you to practice using the formula to calculate the dosage.
Make sure you include the correct form (g, mg, mL, etc.) when making your calculations. The first
one has been set up for you. Note: If the quantity (Q) is larger than 1, you may want to simplify
(cancel) before multiplying.
Dosage formula: D x Q = one dose
H
1. Order: 500 mg (D) 500 mg x (Q) 1 tablet = ____________
2. Order: 1 g
Supply on hand: 0.5 g per capsule
3. Order: 50 mg
Supply on hand: 25 mg per 5 mL
4. Order: 1000 mg
Supply on hand: 2000 mg per scored tablet
5. Order: 500 mg
Supply on hand: 125 mg per caplet
6. Order: 250 mg
Supply on hand: 125 mg per capsule
7. Order: 25 mg
Supply on hand: 100 mg per 20 mL
8. Order: 75 mg
Supply on hand: 5 mg per 20 mL
9. Order: 5 mg
Supply on hand: 32 mg per 8 mL
10. Order: 500 mg
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Worksheet 3B: Filling Complete Prescriptions Name ________________________
Maria now wants you to calculate the individual dose, the daily dose, and the total amount needed to
fill the complete prescription for several patients. Refer to your abbreviations list to help you decode
the prescription information, if needed. Remember to write the form of medication in your answer.
Prescription Single dose Daily dose Complete prescription
Ampicillin 500 mg po qid x 5 d
On hand: 250 mg capsules _________ _________ _____________
Digoxin elixir 150 mcg po tid x 10 d
On hand: 50 mcg/mL _________ _________ _____________
Codeine sulfate 60 mg po q4h x 7 d
On hand: 30 mg tablets _________ _________ _____________
Clondine 0.4 mg po bid x 3 d
On hand: 0.1 mg tablets _________ _________ _____________
Amoxicillin 250 mg po qid x 10 d
On hand: 125 mg capsules _________ _________ _____________
Lasix 40 mg po qd x 30 d
On hand: 20 mg tablets _________ _________ _____________
Ampicillintrihydrate 250 mg po qid x 10 d
On hand: 125 mg per 5 mL _________ _________ _____________
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Quiz: Calculating Dosage Name ______________________
For each of the following doctor’s orders, calculate the individual dose of medication.
1. Dr. Jones prescribed Plendil 7.5 mg. The drug label reads: Plendil 2.5 mg tab.
2. The doctor ordered Dilaudid 1.5 mg IM from a vial that is labeled 0.6 mg per mL
3. Dr. Sam prescribed 20 mg of a medication. You have 10 mg per 5 mL.
4. The physician ordered Procardia XL 60 mg. The drug on hand is Procardia XL 30 mg tablets.
5. Dr. Garza prescribed 30 mg of Phenobarbital. The pharmacy has 15 mg capsules available.
For each of the following prescriptions, calculate the individual dose, the daily dose, and the total
amount needed to fill the complete prescription.
Single dose Daily dose Total amount
6. Amoxicillin 500 mg capsule po tid x 10 d
On hand: 500 mg/1 capsule _________ _________ __________
7. Prednisone 40 mg po bid x 3 d
8. Ciprofloxin 750 mg po qd x 10 d
On hand: 500 mg scored tablet _________ _________ __________
9. PenVK 250 mg po qid x 10 d
On hand: PenVK 250 mg/1 tsp _________ _________ __________
10. Acetaminophen 500 mg tab po q4h x 5 d
On hand: 250 mg/1 tablet _________ _________ __________
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Worksheet 1: Prescription Abbreviations Answer Key
1. qid __G___
A. by mouth or orally
2. hs ___M___
B. liquid or syrup
3. bid ___O___
C. every day
4. g ___N___
D. three times a day
5. mg ___F___
E. medication inserted rectally
6. po ___A___
F. milligram
7. qd ___C___
G. four times a day
8. gr ___K___
H. every 6 hours
9. U ___L___
I. milliliters
10. tid __ D___
J. as needed
11. Elix. __ B___
K. grain
12. Supp. __E___
L. Unit
13. q6h __H___
M. at the hour of sleep; bedtime
14. mL __I____
N. gram
15. prn __J____
O. twice a day
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Worksheet 2: Decoding Prescriptions Answer Key
Answers will vary depending on the prescriptions used for this activity
The patient’s full name
The date
The drug name in manufacturer or generic
format
The doctor’s order for dosage amount (how
much medication)
The administration route (by mouth, IV,
injection)
The frequency with which the patient is to
take the medication
The duration, the number of days that the
patient is to take the medication
The total quantity or amount that the
pharmacist is to dispense
A check-off or box allowing a generic
substitute (if provided)
The physician’s name
The physician’s DEA number
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Worksheet 3A: Calculating Dosage Answer Key
Dosage Formula: D x Q = drug dose
H
1. Order: 500 mg
2. Order: 1 g
3. Order: 50 mg
4. Order: 1000 mg
5. Order: 500 mg
6. Order: 250 mg
7. Order: 25mg
8. Order: 75 mg
9. Order: 5 mg
10. Order: 500 mg
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Worksheet 3B: Filling Complete Prescriptions Answer Key
Prescription Single dose Daily dose Complete prescription
Ampicillin 500 mg po qid x 5 d
On hand: 250 mg capsules 2 capsules 8 capsules 40 capsules
Digoxin elixir 150 mcg po tid x 10 d
On hand: 50 mcg/mL 3 mL 9 mL 90 mL
Codeine sulfate 60 mg po q4h x 7 d
On hand: 30 mg tablets 2 tab 12 tab 84 tab
Clondine 0.4 mg po bid x 3 d
On hand: 0.1 mg tablets 4 tab 8 tab 24 tab
Amoxicillin 250 mg po qid x 10 d
On hand: 125 mg capsules 2 tab 8 tab 80 tab
Lasix 40 mg po qd x 30 d
On hand: 20 mg tablets 2 tab 2 tab 60 tab
Ampicillintrihydrate 250 mg po qid x 10 d
On hand: 125 mg per 5 mL 10 mL 40 mL 400 mL
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Quiz: Calculating Dosage Answer Key
For each of the following doctor’s orders, calculate the individual dose of medication:
1. Dr. Jones prescribed Plendil 7.5 mg. The drug label reads: Plendil 2.5 mg tab.
3 tab
2. The doctor ordered Dilaudid 1.5 mg IM from a vial that is labeled 0.6 mg per mL
2.5 mL
3. Dr. Sam prescribed 20 mg of a medication. You have 10 mg per 5 mL.
10 mL
4. The physician ordered Procardia XL 60 mg. The drug on hand is Procardia XL 30 mg tablets.
2 tab
5. Dr. Garza prescribed 30 mg of Phenobarbital. The pharmacy has 15 mg capsules available.
2 capsules
For each of the following prescriptions, calculate the individual dose, the daily dose, and the total
amount needed to fill the complete prescription.
Single dose Daily dose Total amount
6. Amoxicillin 500 mg capsule po tid x 10 d
On hand: 500 mg/1 capsule 1 capsule 3 capsules 30 capsules
7. Prednisone 40 mg po bid x 3 d
8. Ciprofloxin 750 mg po qd x 10 d
On hand: 500 mg scored tablet 1 ½ tabs 1 ½ tabs 15 tabs
9. PenVK 250 mg po qid x 10 d
On hand: PenVK 250 mg/1 tsp 1 tsp 4 tsp 40 tsp
10. Acetaminophen 500 mg tab po q4h x 5 d
On hand: 250 mg/1 tablet 2 tabs 12 tabs 60 tabs
