Kaplan Dosage Calculation: Topics and Worked Problems
Shows the work. Every example is computed with the formula and numbered steps. For study and exam practice, not for patient care.
Kaplan publishes NCLEX prep and, for nursing programs, integrated testing and content review. Two of its public pages describe medication math. This page summarizes them and works a problem for each topic, without reproducing Kaplan’s content.
What Kaplan’s pages describe
- Topics. Kaplan’s guide to medication calculation lists oral medications, parenteral medications, reconstituting, weight-based calculations, IV calculations, heparin calculations, drop factor calculations, insulin dosages, and critical care calculations, plus the algebra and conversions underneath them (setting up proportions, pounds to kilograms, and other units).
- Methods. Kaplan’s content review for nursing programs includes a Drug Dosage and Calculation Workshop in three sections: Basic Math, Ratio and Proportion, and Dimensional Analysis.
- Answer format. Kaplan’s guide to NCLEX fill-in-the-blank items says to enter only the number, with no unit, and that rounding rules are usually given in the question. It also points out the on-screen calculator.
One worked problem per topic
Heparin
A heparin infusion of 12,500 units in 250 mL is running at 20 mL/hr. How many units/hr is the client receiving?
- Solve for
- Dose per hour
- Pump rate
- 20 mL/hr
- Drug in the bag
- 12,500 units
- Bag volume
- 250 mL
Formula mL/hr = ordered units/hr ÷ units per mL.
- Concentration = 12,500 units ÷ 250 mL = 50 units/mL.
- units/hr = 20 mL/hr × 50 units/mL = 1,000 units/hr.
- 1,000 units/hr is exact, so no rounding is needed.
Answer 1,000 units/hr
Insulin
The sliding scale reads: 150 to 199 mg/dL, 2 units; 200 to 249 mg/dL, 4 units; 250 to 299 mg/dL, 6 units; 300 to 349 mg/dL, 8 units; 350 to 400 mg/dL, 10 units. The client's blood glucose is 395 mg/dL. How many units?
- Blood glucose
- 395 mg/dL
- Scale
- 150 mg/dL–199 mg/dL–2 units; 200 mg/dL–249 mg/dL–4 units; 250 mg/dL–299 mg/dL–6 units; 300 mg/dL–349 mg/dL–8 units; 350 mg/dL–400 mg/dL–10 units
Formula Give the units of the scale row that holds the blood glucose.
- Find the scale row that holds 395 mg/dL: 350 to 400 mg/dL.
- That row gives 10 units.
- 10 units is exact, so no rounding is needed.
Answer 10 units
Drop factor
Order: levofloxacin 250 mg in 50 mL IV over 90 minutes. The secondary tubing has a drop factor of 20 gtt/mL. How many gtt/min?
- Volume
- 50 mL
- Infusion time
- 90 minutes
- Drop factor
- 20 gtt/mL
Formula gtt/min = volume × drop factor ÷ minutes.
- gtt/min = volume × drop factor ÷ minutes.
- 50 mL × 20 gtt/mL ÷ 90 minutes = 11.11 gtt/min.
- A drop cannot be split, so round to a whole number: 11 gtt/min.
Answer 11 gtt/min
Reconstituting
Penicillin G 5 million units is ordered. How many full doses does a 20 million unit vial provide?
- Solve for
- Full doses per vial
- Vial amount
- 20,000,000 units
- Dose
- 5,000,000 units
Formula mL = ordered dose ÷ concentration after mixing.
- Doses = vial amount ÷ dose = 20 million units ÷ 5 million units = 4.
- Only full doses count, so round down: 4 doses.
Answer 4 doses
IV calculation
Lactated Ringer's solution 500 mL is infusing at 125 mL/hr. How many hours will the infusion take?
- Solve for
- Infusion time (hours)
- Volume
- 500 mL
- Rate
- 125 mL/hr
Formula mL/hr = total volume ÷ total hours.
- Hours = volume ÷ rate.
- 500 mL ÷ 125 mL/hr = 4 hours.
- 4 hours is exact, so no rounding is needed.
Answer 4 hours
Critical care
Order: dopamine 2.5 mcg/kg/min IV. Available: dopamine 400 mg in 250 mL. The client weighs 123 kg. At how many mL/hr?
- Solve for
- Pump rate (mL/hr)
- Ordered dose
- 2.5 mcg/kg/min
- Weight
- 123 kg
- Drug in the bag
- 400 mg
- Bag volume
- 250 mL
Formula mL/hr = mcg/kg/min × kg × 60 ÷ mcg per mL.
- Concentration = 400,000 mcg ÷ 250 mL = 1,600 mcg/mL.
- Dose per hour = 2.5 mcg/kg/min × 123 kg × 60 min/hr = 18,450 mcg/hr.
- mL/hr = 18,450 mcg/hr ÷ 1,600 mcg/mL = 11.53 mL/hr.
- Below 100 mL/hr the pump is set to the nearest tenth: 11.5 mL/hr.
Answer 11.5 mL/hr
How to prepare
- Practice every topic on the list, not only the ones you find easy: heparin, insulin, and critical care drips are where many students lose points.
- Set each problem up the same way every time, with units written, so the units check your work.
- The calculators cover each of these topics and show every step.
Kaplan is a registered trademark of Kaplan, Inc. DoseRightRN is independent: it is not affiliated with, endorsed by, or sponsored by the exam's owner, and uses the exam's name only to describe what the page covers.
Sources
- How to master medication calculation math — Kaplan Test Prep
- Nursing education: content review (Drug Dosage and Calculation Workshop) — Kaplan Test Prep
- NCLEX-RN alternate format questions: fill-in-the-blank — Kaplan Test Prep
- Clinical Calculations: With Applications to General and Specialty Areas — Elsevier (Kee, Marshall, et al.)