Calculating Drug Dosages: A Patient-Safe Approach To Nursing And Math 3rd Edition

Calculating Drug Dosages: A Patient-Safe Approach To Nursing And
Math 3rd Edition


1. A patient is prescribed 500 mg of a medication. The available tablets are 250 mg each. How
many tablets should the nurse administer?
A) 1 tablet
B) 1.5 tablets
C) 2 tablets
D) 2.5 tablets
Correct Answer: C) 2 tablets
Rationale: Using the formula D/H × Q = A (Desired ÷ Have × Quantity), 500 mg ÷ 250 mg × 1
tablet = 2 tablets. This is a basic ratio calculation fundamental to safe medication
administration.

2. The physician orders 0.5 g of a drug. The pharmacy supplies 250 mg tablets. How many
tablets will the nurse give?
A) 1 tablet
B) 2 tablets
C) 3 tablets
D) 4 tablets
Correct Answer: B) 2 tablets
Rationale: First, convert 0.5 g to mg: 0.5 × 1000 = 500 mg. Then 500 mg ÷ 250 mg = 2 tablets.
Always ensure unit consistency before calculating.

3. A medication is available as 40 mg/5 mL. The order is for 60 mg. How many mL should be
administered?
A) 5 mL
B) 7.5 mL
C) 10 mL
D) 12.5 mL
Correct Answer: B) 7.5 mL
Rationale: Use ratio-proportion: 40 mg / 5 mL = 60 mg / X mL. Cross-multiply: 40X = 300, X = 7.5
mL. This is a common liquid medication calculation.

4. The order reads: "Administer 1.5 L of IV fluid over 12 hours." What is the hourly rate in
mL/hr?
A) 100 mL/hr
B) 125 mL/hr

,C) 150 mL/hr
D) 175 mL/hr
Correct Answer: B) 125 mL/hr
Rationale: Convert 1.5 L to mL: 1.5 × 1000 = 1500 mL. Then 1500 mL ÷ 12 hours = 125 mL/hr.
This is a standard IV flow rate calculation.

5. A patient weighs 220 lbs. What is the weight in kg? (Round to nearest tenth)
A) 99.0 kg
B) 100.0 kg
C) 110.0 kg
D) 120.0 kg
Correct Answer: B) 100.0 kg
Rationale: Use the conversion 2.2 lbs = 1 kg. 220 lbs ÷ 2.2 = 100 kg. Accurate weight conversion
is critical for weight-based dosing.

6. The nurse needs to administer 0.125 mg of digoxin. The available tablets are 0.25 mg. How
many tablets should be given?
A) 0.25 tablet
B) 0.5 tablet
C) 0.75 tablet
D) 1 tablet
Correct Answer: B) 0.5 tablet
Rationale: D/H × Q = 0.125 mg ÷ 0.25 mg × 1 tablet = 0.5 tablet. This demonstrates calculation
of a fraction of a tablet when scored tablets are available.

7. A patient is receiving an IV infusion at 125 mL/hr. How many mL will infuse in 8 hours?
A) 800 mL
B) 900 mL
C) 1000 mL
D) 1100 mL
Correct Answer: C) 1000 mL
Rationale: 125 mL/hr × 8 hours = 1000 mL. This is a straightforward multiplication for total
volume infused over time.

8. The order is for 30 mg of a liquid medication. The label reads 15 mg/5 mL. How many mL
will the nurse administer?
A) 5 mL
B) 10 mL
C) 15 mL
D) 20 mL

, Correct Answer: B) 10 mL
Rationale: 15 mg / 5 mL = 30 mg / X mL. Cross-multiply: 15X = 150, X = 10 mL.

9. A patient is to receive 1 g of a medication IV. The vial contains 500 mg/2 mL. How many mL
will be needed?
A) 2 mL
B) 3 mL
C) 4 mL
D) 5 mL
Correct Answer: C) 4 mL
Rationale: Convert 1 g to 1000 mg. 1000 mg ÷ 500 mg × 2 mL = 4 mL.

10. The physician orders 75 mg of meperidine IM. The available syringe contains 100 mg/mL.
How many mL should the nurse administer?
A) 0.5 mL
B) 0.75 mL
C) 1 mL
D) 1.25 mL
Correct Answer: B) 0.75 mL
Rationale: D/H × Q = 75 mg ÷ 100 mg × 1 mL = 0.75 mL.

11. A patient is prescribed 2 L of IV fluid to run over 24 hours. What is the hourly rate?
A) 75 mL/hr
B) 80 mL/hr
C) 83.3 mL/hr
D) 90 mL/hr
Correct Answer: C) 83.3 mL/hr
Rationale: 2 L = 2000 mL. 2000 mL ÷ 24 hours = 83.3 mL/hr (rounded). This is a common
maintenance IV rate.

12. The order is for heparin 5000 units subcutaneously. The vial is labeled 10,000 units/mL.
How many mL will the nurse administer?
A) 0.25 mL
B) 0.5 mL
C) 0.75 mL
D) 1 mL
Correct Answer: B) 0.5 mL
Rationale: 5000 units ÷ 10,000 units/mL = 0.5 mL.