Pharmacology Dosage Calculations Exam Prep – Real Practice Questions, Answers
& Detailed Rationales (Updated 2026) | Medication Dosage Calculations, IV Flow
Rate & Drip Calculations, Pediatric & Weight-Based Dosing, Unit Conversions &
Dimensional Analysis, Safe Medication Administration, Oral & Injectable Medication
Math, Pharmacology Safety Principles & NCLEX-Style Calculation Problems
Question 1: A physician orders 0.5 g of amoxicillin oral suspension. The pharmacy
supplies the medication as 250 mg/5 mL. How many milliliters should the nurse
administer?
A. 2.5 mL
B. 5 mL
C. 10 mL
D. 15 mL
CORRECT ANSWER: C. 10 mL
Rationale: First, convert 0.5 g to mg: 0.5 g × 1000 = 500 mg. Using ratio and proportion:
250 mg/5 mL = 500 mg/x mL. Cross multiply: 250x = 2500, therefore x = 10 mL.
Question 2: A patient weighing 176 lb is prescribed a medication at 5 mg/kg. What is
the total dose in milligrams?
A. 200 mg
B. 300 mg
C. 400 mg
D. 500 mg
CORRECT ANSWER: C. 400 mg
Rationale: Convert pounds to kilograms: 176 lb ÷ 2.2 = 80 kg. Multiply weight by dose: 80
kg × 5 mg/kg = 400 mg.
Question 3: An IV infusion of 1000 mL D5W is to infuse over 8 hours. What is the
flow rate in mL/hr?
A. 100 mL/hr
B. 115 mL/hr
C. 125 mL/hr
D. 150 mL/hr
CORRECT ANSWER: C. 125 mL/hr
Rationale: Divide total volume by time: 1000 mL ÷ 8 hr = 125 mL/hr.
Question 4: A medication order reads "Give 250 mcg digoxin IV push." The vial is
labeled 0.5 mg/mL. How many milliliters should be administered?
A. 0.25 mL
B. 0.5 mL
C. 0.75 mL
D. 1.0 mL
,CORRECT ANSWER: B. 0.5 mL
Rationale: Convert 250 mcg to mg: 250 mcg ÷ 1000 = 0.25 mg. Use ratio: 0.5 mg/1 mL =
0.25 mg/x mL. Cross multiply: 0.5x = 0.25, therefore x = 0.5 mL.
Question 5: A pediatric patient weighs 33 lb. The safe dose range for a medication is
10-15 mg/kg/day in divided doses every 8 hours. What is the maximum single dose
in milligrams?
A. 50 mg
B. 65 mg
C. 75 mg
D. 90 mg
CORRECT ANSWER: C. 75 mg
Rationale: Convert weight: 33 lb ÷ 2.2 = 15 kg. Maximum daily dose: 15 kg × 15 mg/kg =
225 mg/day. Divided every 8 hours = 3 doses/day. Single dose: 225 mg ÷ 3 = 75 mg.
Question 6: An IV bag contains 500 mL of normal saline with 20,000 units of
heparin. The order is to infuse at 1000 units/hr. What is the flow rate in mL/hr?
A. 20 mL/hr
B. 25 mL/hr
C. 30 mL/hr
D. 40 mL/hr
CORRECT ANSWER: B. 25 mL/hr
Rationale: Determine concentration: 20,000 units/500 mL = 40 units/mL. Calculate flow
rate: 1000 units/hr ÷ 40 units/mL = 25 mL/hr.
Question 7: A medication is supplied as 1 g powder for reconstitution. The label
states: "Add 9.6 mL sterile water to yield 100 mg/mL." How many milliliters should
be administered for a 250 mg dose?
A. 1.5 mL
B. 2.5 mL
C. 3.5 mL
D. 4.5 mL
CORRECT ANSWER: B. 2.5 mL
Rationale: After reconstitution, concentration is 100 mg/mL. For a 250 mg dose: 250 mg
÷ 100 mg/mL = 2.5 mL.
Question 8: An IV infusion is running at 30 gtt/min with tubing that has a drop factor
of 15 gtt/mL. What is the flow rate in mL/hr?
A. 90 mL/hr
B. 120 mL/hr
,C. 150 mL/hr
D. 180 mL/hr
CORRECT ANSWER: B. 120 mL/hr
Rationale: Use formula: (gtt/min × 60 min/hr) ÷ drop factor = mL/hr. (30 × 60) ÷ 15 = 1800
÷ 15 = 120 mL/hr.
Question 9: A patient is prescribed morphine sulfate 8 mg IM. The available
concentration is 10 mg/mL. How many milliliters should be drawn up?
A. 0.6 mL
B. 0.8 mL
C. 1.0 mL
D. 1.2 mL
CORRECT ANSWER: B. 0.8 mL
Rationale: Use ratio: 10 mg/1 mL = 8 mg/x mL. Cross multiply: 10x = 8, therefore x = 0.8
mL.
Question 10: A child weighs 44 lb. The order is for acetaminophen 15 mg/kg. The
suspension available is 160 mg/5 mL. How many milliliters should be
administered?
A. 7.5 mL
B. 9.4 mL
C. 12 mL
D. 15 mL
CORRECT ANSWER: B. 9.4 mL
Rationale: Convert weight: 44 lb ÷ 2.2 = 20 kg. Calculate dose: 20 kg × 15 mg/kg = 300
mg. Concentration: 160 mg/5 mL = 32 mg/mL. Volume: 300 mg ÷ 32 mg/mL = 9.375 mL
≈ 9.4 mL.
Question 11: An IV order reads: "Infuse 1500 mL over 12 hours." What is the drip rate
in gtt/min if the drop factor is 20 gtt/mL?
A. 30 gtt/min
B. 42 gtt/min
C. 50 gtt/min
D. 60 gtt/min
CORRECT ANSWER: B. 42 gtt/min
Rationale: First calculate mL/hr: 1500 mL ÷ 12 hr = 125 mL/hr. Then: (125 mL/hr × 20
gtt/mL) ÷ 60 min/hr = 2500 ÷ 60 = 41.67 ≈ 42 gtt/min.
Question 12: A medication vial contains 500 mg of powder. Instructions state: "Add
4.8 mL diluent to yield 100 mg/mL." What is the total volume after reconstitution?
, A. 4.8 mL
B. 5.0 mL
C. 5.2 mL
D. 10 mL
CORRECT ANSWER: B. 5.0 mL
Rationale: If concentration after reconstitution is 100 mg/mL and total drug is 500 mg,
total volume = 500 mg ÷ 100 mg/mL = 5.0 mL. The powder displacement is 0.2 mL (5.0
mL - 4.8 mL diluent).
Question 13: A patient receives an IV infusion of dopamine at 5 mcg/kg/min. The
patient weighs 70 kg. The IV bag contains 400 mg dopamine in 250 mL D5W. What is
the infusion rate in mL/hr?
A. 10.5 mL/hr
B. 13.1 mL/hr
C. 15.8 mL/hr
D. 20 mL/hr
CORRECT ANSWER: B. 13.1 mL/hr
Rationale: Calculate dose/min: 5 mcg/kg/min × 70 kg = 350 mcg/min. Convert to mg/hr:
350 mcg/min × 60 min/hr = 21,000 mcg/hr = 21 mg/hr. Concentration: 400 mg/250 mL =
1.6 mg/mL. Rate: 21 mg/hr ÷ 1.6 mg/mL = 13.125 mL/hr ≈ 13.1 mL/hr.
Question 14: A prescription reads: "Give 1.5 g of medication X." The available
tablets are 500 mg each. How many tablets should be administered?
A. 1 tablet
B. 2 tablets
C. 3 tablets
D. 4 tablets
CORRECT ANSWER: C. 3 tablets
Rationale: Convert 1.5 g to mg: 1.5 g × 1000 = 1500 mg. Number of tablets: 1500 mg ÷
500 mg/tablet = 3 tablets.
Question 15: An IV piggyback medication of 50 mL is to infuse over 30 minutes.
What is the flow rate in mL/hr?
A. 50 mL/hr
B. 100 mL/hr
C. 150 mL/hr
D. 200 mL/hr
CORRECT ANSWER: B. 100 mL/hr
Rationale: 30 minutes = 0.5 hours. Flow rate: 50 mL ÷ 0.5 hr = 100 mL/hr.
& Detailed Rationales (Updated 2026) | Medication Dosage Calculations, IV Flow
Rate & Drip Calculations, Pediatric & Weight-Based Dosing, Unit Conversions &
Dimensional Analysis, Safe Medication Administration, Oral & Injectable Medication
Math, Pharmacology Safety Principles & NCLEX-Style Calculation Problems
Question 1: A physician orders 0.5 g of amoxicillin oral suspension. The pharmacy
supplies the medication as 250 mg/5 mL. How many milliliters should the nurse
administer?
A. 2.5 mL
B. 5 mL
C. 10 mL
D. 15 mL
CORRECT ANSWER: C. 10 mL
Rationale: First, convert 0.5 g to mg: 0.5 g × 1000 = 500 mg. Using ratio and proportion:
250 mg/5 mL = 500 mg/x mL. Cross multiply: 250x = 2500, therefore x = 10 mL.
Question 2: A patient weighing 176 lb is prescribed a medication at 5 mg/kg. What is
the total dose in milligrams?
A. 200 mg
B. 300 mg
C. 400 mg
D. 500 mg
CORRECT ANSWER: C. 400 mg
Rationale: Convert pounds to kilograms: 176 lb ÷ 2.2 = 80 kg. Multiply weight by dose: 80
kg × 5 mg/kg = 400 mg.
Question 3: An IV infusion of 1000 mL D5W is to infuse over 8 hours. What is the
flow rate in mL/hr?
A. 100 mL/hr
B. 115 mL/hr
C. 125 mL/hr
D. 150 mL/hr
CORRECT ANSWER: C. 125 mL/hr
Rationale: Divide total volume by time: 1000 mL ÷ 8 hr = 125 mL/hr.
Question 4: A medication order reads "Give 250 mcg digoxin IV push." The vial is
labeled 0.5 mg/mL. How many milliliters should be administered?
A. 0.25 mL
B. 0.5 mL
C. 0.75 mL
D. 1.0 mL
,CORRECT ANSWER: B. 0.5 mL
Rationale: Convert 250 mcg to mg: 250 mcg ÷ 1000 = 0.25 mg. Use ratio: 0.5 mg/1 mL =
0.25 mg/x mL. Cross multiply: 0.5x = 0.25, therefore x = 0.5 mL.
Question 5: A pediatric patient weighs 33 lb. The safe dose range for a medication is
10-15 mg/kg/day in divided doses every 8 hours. What is the maximum single dose
in milligrams?
A. 50 mg
B. 65 mg
C. 75 mg
D. 90 mg
CORRECT ANSWER: C. 75 mg
Rationale: Convert weight: 33 lb ÷ 2.2 = 15 kg. Maximum daily dose: 15 kg × 15 mg/kg =
225 mg/day. Divided every 8 hours = 3 doses/day. Single dose: 225 mg ÷ 3 = 75 mg.
Question 6: An IV bag contains 500 mL of normal saline with 20,000 units of
heparin. The order is to infuse at 1000 units/hr. What is the flow rate in mL/hr?
A. 20 mL/hr
B. 25 mL/hr
C. 30 mL/hr
D. 40 mL/hr
CORRECT ANSWER: B. 25 mL/hr
Rationale: Determine concentration: 20,000 units/500 mL = 40 units/mL. Calculate flow
rate: 1000 units/hr ÷ 40 units/mL = 25 mL/hr.
Question 7: A medication is supplied as 1 g powder for reconstitution. The label
states: "Add 9.6 mL sterile water to yield 100 mg/mL." How many milliliters should
be administered for a 250 mg dose?
A. 1.5 mL
B. 2.5 mL
C. 3.5 mL
D. 4.5 mL
CORRECT ANSWER: B. 2.5 mL
Rationale: After reconstitution, concentration is 100 mg/mL. For a 250 mg dose: 250 mg
÷ 100 mg/mL = 2.5 mL.
Question 8: An IV infusion is running at 30 gtt/min with tubing that has a drop factor
of 15 gtt/mL. What is the flow rate in mL/hr?
A. 90 mL/hr
B. 120 mL/hr
,C. 150 mL/hr
D. 180 mL/hr
CORRECT ANSWER: B. 120 mL/hr
Rationale: Use formula: (gtt/min × 60 min/hr) ÷ drop factor = mL/hr. (30 × 60) ÷ 15 = 1800
÷ 15 = 120 mL/hr.
Question 9: A patient is prescribed morphine sulfate 8 mg IM. The available
concentration is 10 mg/mL. How many milliliters should be drawn up?
A. 0.6 mL
B. 0.8 mL
C. 1.0 mL
D. 1.2 mL
CORRECT ANSWER: B. 0.8 mL
Rationale: Use ratio: 10 mg/1 mL = 8 mg/x mL. Cross multiply: 10x = 8, therefore x = 0.8
mL.
Question 10: A child weighs 44 lb. The order is for acetaminophen 15 mg/kg. The
suspension available is 160 mg/5 mL. How many milliliters should be
administered?
A. 7.5 mL
B. 9.4 mL
C. 12 mL
D. 15 mL
CORRECT ANSWER: B. 9.4 mL
Rationale: Convert weight: 44 lb ÷ 2.2 = 20 kg. Calculate dose: 20 kg × 15 mg/kg = 300
mg. Concentration: 160 mg/5 mL = 32 mg/mL. Volume: 300 mg ÷ 32 mg/mL = 9.375 mL
≈ 9.4 mL.
Question 11: An IV order reads: "Infuse 1500 mL over 12 hours." What is the drip rate
in gtt/min if the drop factor is 20 gtt/mL?
A. 30 gtt/min
B. 42 gtt/min
C. 50 gtt/min
D. 60 gtt/min
CORRECT ANSWER: B. 42 gtt/min
Rationale: First calculate mL/hr: 1500 mL ÷ 12 hr = 125 mL/hr. Then: (125 mL/hr × 20
gtt/mL) ÷ 60 min/hr = 2500 ÷ 60 = 41.67 ≈ 42 gtt/min.
Question 12: A medication vial contains 500 mg of powder. Instructions state: "Add
4.8 mL diluent to yield 100 mg/mL." What is the total volume after reconstitution?
, A. 4.8 mL
B. 5.0 mL
C. 5.2 mL
D. 10 mL
CORRECT ANSWER: B. 5.0 mL
Rationale: If concentration after reconstitution is 100 mg/mL and total drug is 500 mg,
total volume = 500 mg ÷ 100 mg/mL = 5.0 mL. The powder displacement is 0.2 mL (5.0
mL - 4.8 mL diluent).
Question 13: A patient receives an IV infusion of dopamine at 5 mcg/kg/min. The
patient weighs 70 kg. The IV bag contains 400 mg dopamine in 250 mL D5W. What is
the infusion rate in mL/hr?
A. 10.5 mL/hr
B. 13.1 mL/hr
C. 15.8 mL/hr
D. 20 mL/hr
CORRECT ANSWER: B. 13.1 mL/hr
Rationale: Calculate dose/min: 5 mcg/kg/min × 70 kg = 350 mcg/min. Convert to mg/hr:
350 mcg/min × 60 min/hr = 21,000 mcg/hr = 21 mg/hr. Concentration: 400 mg/250 mL =
1.6 mg/mL. Rate: 21 mg/hr ÷ 1.6 mg/mL = 13.125 mL/hr ≈ 13.1 mL/hr.
Question 14: A prescription reads: "Give 1.5 g of medication X." The available
tablets are 500 mg each. How many tablets should be administered?
A. 1 tablet
B. 2 tablets
C. 3 tablets
D. 4 tablets
CORRECT ANSWER: C. 3 tablets
Rationale: Convert 1.5 g to mg: 1.5 g × 1000 = 1500 mg. Number of tablets: 1500 mg ÷
500 mg/tablet = 3 tablets.
Question 15: An IV piggyback medication of 50 mL is to infuse over 30 minutes.
What is the flow rate in mL/hr?
A. 50 mL/hr
B. 100 mL/hr
C. 150 mL/hr
D. 200 mL/hr
CORRECT ANSWER: B. 100 mL/hr
Rationale: 30 minutes = 0.5 hours. Flow rate: 50 mL ÷ 0.5 hr = 100 mL/hr.
