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NCLEX-RN Dosage calculation practice questions

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These are original practice items written to the NCLEX-RN blueprint (4 options, no penalty for wrong answers), not actual exam questions. Try each one before you open the answer.

What this topic covers

Dosage calculation sits inside the Pharmacological and Parenteral Therapies category of the NCLEX-RN. Our bank holds 44 verified items tagged to it, and the 4 below are a fixed sample so the page stays the same every time you open it. Each one shows the reasoning, not just the letter.

The topic tag comes from our own items rather than from a published syllabus, so treat it as a map of what we cover. For the official category breakdown see the NCLEX-RN page.

Dosage calculation sample questions

Question 1

A 45-year-old female in the oncology unit is prescribed ondansetron 0.15 mg/kg intravenously 30 minutes before chemotherapy. The client weighs 70 kg. The pharmacy supplies ondansetron as 2 mg/mL in a 4 mL vial. How many milliliters should the nurse administer?

  1. A 4.50 mL
  2. B 5.25 mL
  3. C 2.50 mL
  4. D 3.75 mL
Show the answer and explanation

Correct answer: B

Dose: 0.15 mg/kg x 70 kg = 10.5 mg. Volume: 10.5 mg divided by 2 mg/mL = 5.25 mL.

Why the other options are wrong:
A: 4.50 mL delivers only 9 mg, the dose for a 60-kg client, so the weight was likely misapplied.
C: 2.50 mL delivers only 5 mg, less than half of the calculated 10.5-mg dose.
D: 3.75 mL delivers 7.5 mg, which matches a 50-kg weight rather than 70 kg.

Question 2

A 66-year-old client in the critical care unit is ordered to receive an intravenous infusion of dopamine 800 mg in 500 mL of 5% dextrose in water. The client's weight is 70 kg. The prescribed dose is 5 mcg/kg/min. The nurse has a pump that delivers in mL/hr. What rate should the nurse set the pump?

  1. A 8.7 mL/hr.
  2. B 6.5 mL/hr.
  3. C 26.3 mL/hr.
  4. D 13.1 mL/hr.
Show the answer and explanation

Correct answer: D

Dose: 5 mcg/kg/min x 70 kg = 350 mcg/min, and 350 x 60 = 21,000 mcg/hr (21 mg/hr). Concentration: 800 mg / 500 mL = 1.6 mg/mL. Rate: 21 mg/hr / 1.6 mg/mL = 13.1 mL/hr.

Why the other options are wrong:
A: 8.7 mL/hr delivers only about 3.3 mcg/kg/min, an underdose from a conversion error.
B: 6.5 mL/hr is half the correct rate, as if the bag held 800 mg in 250 mL (3.2 mg/mL).
C: 26.3 mL/hr is double the correct rate, as if the concentration were 0.8 mg/mL, and delivers about 10 mcg/kg/min.

Question 3

A 70-year-old client with a urinary tract infection is prescribed ciprofloxacin 400 mg IV every 12 hours. The pharmacy supplies a vial containing 200 mg/mL. How many mL should the nurse administer?

  1. A Administer 2 mL from the vial.
  2. B Administer 4 mL from the vial.
  3. C Administer 0.5 mL from the vial.
  4. D Administer 1 mL from the vial.
Show the answer and explanation

Correct answer: A

Use desired dose over dose on hand: 400 mg divided by 200 mg/mL equals 2 mL.

Why the other options are wrong:
B: 4 mL contains 800 mg, which is twice the ordered dose.
C: 0.5 mL comes from inverting the formula (200 divided by 400) and contains only 100 mg.
D: 1 mL contains only 200 mg, half of the ordered 400 mg dose.

Question 4

A 40-year-old client in the emergency department with diabetic ketoacidosis is prescribed an intravenous infusion of regular insulin at 0.1 unit/kg/hr. The client weighs 85 kg. The insulin concentration is 50 units of regular insulin in 100 mL of 0.9% sodium chloride. At what rate in mL/hr should the nurse set the infusion pump?

  1. A 12.75 mL/hr
  2. B 17 mL/hr
  3. C 8.5 mL/hr
  4. D 34 mL/hr
Show the answer and explanation

Correct answer: B

Dose: 0.1 unit/kg/hr x 85 kg = 8.5 units/hr. Concentration: 50 units divided by 100 mL = 0.5 unit/mL. Rate: 8.5 units/hr divided by 0.5 unit/mL = 17 mL/hr.

Why the other options are wrong:
A: 12.75 mL/hr delivers only about 6.4 units/hr, short of the 8.5 units/hr ordered.
C: 8.5 mL/hr enters the units/hr dose as mL/hr, ignoring the concentration, and delivers only 4.25 units/hr.
D: 34 mL/hr delivers 17 units/hr, double the prescribed dose, as if the concentration were 0.25 unit/mL.

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