Calculating Drug Dosages
A Patient-Safe Approach to
Nursing and Math
3rd Edition
• Author(s)Sandra Luz
Martinez de Castillo;
Maryanne Werner-
McCullough
,Chapter 1 —Medication Orders & Tablet
Calculations
Stem
A nurse verifies an ordered oral medication dose of 0.125
mg. The nurse needs to document the dose in micrograms
(mcg). What is the correct dose in mcg?
A. 12.5 mcg
B. 125 mcg
C. 1,250 mcg
D. 12,500 mcg
Correct Answer: B
Rationale
Correct: 0.125 mg × 1,000 mcg/mg = 125 mcg.
A (12.5 mcg): Reflects multiplying by 100 instead of 1,000
(decimal-shift error).
C (1,250 mcg): Reflects multiplying by 10,000 (an extra factor
of 10).
,D (12,500 mcg): Reflects multiplying by 100,000 (too large—
decimal misplacement).
Teaching Point: Always convert mg → mcg by ×1,000 and
double-check decimal placement.
2 — Chapter Reference
Chapter 1. Safety in Medication Administration — Section
1.1: Principles of Medication Safety
Stem
Which of the following best describes the MOST important
step to prevent medication errors at the bedside?
A. Administer medications quickly to reduce patient
discomfort.
B. Verify the five rights of medication administration for each
dose.
C. Rely on memory for commonly given medication doses.
D. Delegate the double-check process to a pharmacy
technician.
Correct Answer: B
, Rationale
Correct: Verifying the five rights (right patient, drug, dose,
route, time) is a foundational safety step.
A: Speed should never override verification — increases
error risk.
C: Memory reliance increases risk of wrong dose; use checks
and references.
D: Responsibility to verify lies with the administering nurse;
delegation is unsafe.
Teaching Point: Use the five rights for every medication,
every time.
3 — Chapter Reference
Chapter 1. Safety in Medication Administration — Section
1.2: The Drug Label & Order Verification
Stem
A medication order reads: “Give 2.5 mg IV q8h.” The vial
label shows 5 mg/mL. How many milliliters should the nurse
prepare for one dose?