🧮 20 questions · answers and rationales · free
NCLEX dosage calculation practice questions
20 free NCLEX-style dosage calculation questions: IV drip rates, weight-based and pediatric doses, mcg/kg/min infusions, insulin and unit conversions, each with the answer worked out.
Tap an answer to check it, or open "Show the answer and rationale" under each question. Every client is fictional. For exam practice only, not medical advice.
Question 1 of 20
A 4-month-old is seen in the clinic and needs a weight-based prescription. The infant weighs 15 lb 6 oz on the clinic scale. What weight in kilograms should the nurse record? (Use 1 kg = 2.2 lb and round to the nearest hundredth.)
- 6.99 kg
- 7.09 kg
- 7.69 kg
- 6.82 kg
Show the answer and rationale
Answer: A
Convert the ounces to pounds first: 6 oz ÷ 16 oz/lb = 0.375 lb, so the infant weighs 15.375 lb, and 15.375 ÷ 2.2 = 6.99 kg. Reading 15 lb 6 oz as 15.6 lb gives 7.09 kg, the most tempting slip, because pounds and ounces are not a decimal system. Dropping the ounces gives 6.82 kg, and dividing by 2 instead of 2.2 gives 7.69 kg; any of these errors carries straight into every weight-based dose.
Question 2 of 20
Minutes after an IV antibiotic is started, a client who weighs 154 lb (70 kg) develops hives, wheezing and throat tightness, with BP 82/48 mm Hg. The infusion has been stopped, and the provider prescribes epinephrine 0.3 mg IM now. The nurse has an ampule of epinephrine 1 mg/mL. How should the nurse give the dose?
- 0.3 mL by IV push through the existing line
- 0.3 mL IM in the upper outer buttock
- 0.3 mL IM in the anterolateral thigh
- 3 mL IM in the anterolateral thigh
Show the answer and rationale
Answer: C
At 1 mg/mL, 0.3 mg ÷ 1 mg/mL = 0.3 mL, and the label gives the adult anaphylaxis dose by IM or subcutaneous injection into the anterolateral thigh, repeated every 5 to 10 minutes if needed. The buttock is the tempting runner-up because the volume is right, but the label warns against it because absorption there may be too poor to treat anaphylaxis. Three mL is 3 mg, a tenfold overdose from treating the strength as 0.1 mg/mL, and pushing the concentrated 1 mg/mL drug IV can cause dangerous dysrhythmias.
Question 3 of 20
A client with preeclampsia with severe features is prescribed a magnesium sulfate loading dose of 4 g IV over 20 minutes. The pharmacy supplies 4 g in 100 mL. At what rate in mL/hr should the nurse program the pump?
- 600 mL/hr
- 100 mL/hr
- 500 mL/hr
- 300 mL/hr
Show the answer and rationale
Answer: D
The full 100 mL must infuse in 20 minutes: 100 mL ÷ 20 min = 5 mL/min, and 5 × 60 = 300 mL/hr. The runner-up, 500 mL/hr, treats 20 minutes as 0.2 hour and pushes the loading dose in about 12 minutes, raising the risk of magnesium toxicity. A rate of 100 mL/hr stretches the load over a full hour and delays seizure protection, and 600 mL/hr halves the infusion time to 10 minutes, an even faster and riskier rate.
Question 4 of 20
Gentamicin 1.7 mg/kg IV every 8 hours is prescribed for a client who weighs 165 lb. The vial contains 40 mg/mL. How many mL should the nurse draw up for each dose? (Round to the nearest tenth of a mL.)
- 7 mL
- 15.4 mL
- 0.3 mL
- 3.2 mL
Show the answer and rationale
Answer: D
Convert the weight first, 165 lb ÷ 2.2 = 75 kg, then 1.7 mg × 75 kg = 127.5 mg per dose, and 127.5 mg ÷ 40 mg/mL = 3.19 mL, rounded to 3.2 mL. Using the weight in pounds gives 7 mL, the most tempting error because every other step is right, and it is an overdose of a drug that can damage the kidneys and hearing. Multiplying by 2.2 instead of dividing gives 15.4 mL, and 0.3 mL comes from inverting the ratio.
Question 5 of 20
A client in septic shock who weighs 70 kg is receiving norepinephrine at 0.05 mcg/kg/min from a bag of 8 mg in 250 mL of dextrose 5% in water. The MAP is 61 mm Hg, and the protocol says to increase the dose by 0.02 mcg/kg/min until the MAP is at least 65 mm Hg. At what rate should the nurse set the pump? (Round to the nearest tenth.)
- 91.9 mL/hr
- 9.2 mL/hr
- 2.6 mL/hr
- 0.2 mL/hr
Show the answer and rationale
Answer: B
Work with the new total dose: 0.05 + 0.02 = 0.07 mcg/kg/min × 70 kg = 4.9 mcg/min, × 60 = 294 mcg/hr; the bag holds 8,000 mcg ÷ 250 mL = 32 mcg/mL, so 294 ÷ 32 = 9.2 mL/hr, up from 6.6 mL/hr. 2.6 mL/hr is the runner-up: it is the correct size of the increase, but setting the pump to it would cut the dose by more than half. 0.2 mL/hr leaves out the 60 minutes, and 91.9 mL/hr converts 8 mg to 800 mcg instead of 8,000 mcg, a tenfold overdose.
Question 6 of 20 · Select all that apply
A nurse is checking unit conversions that a nursing student recorded for several clients. Which conversions are correct? Select all that apply.
- Guaifenesin 1½ teaspoons recorded as 22.5 mL
- An adult's weight of 68 kg recorded as 30.9 lb
- An infant's weight of 9 lb 4 oz recorded as 4.2 kg
- Cyanocobalamin 1,000 mcg recorded as 0.1 mg
- A fluid restriction of 1.8 L recorded as 60 oz
- Magnesium hydroxide 2 tablespoons recorded as 30 mL
Show the answer and rationale
Answer: C, E, F
Nine pounds 4 ounces is 9.25 lb, and 9.25 ÷ 2.2 = 4.2 kg; 2 tablespoons × 15 mL = 30 mL; and 1,800 mL ÷ 30 mL per ounce = 60 oz. The other three hold classic errors. One thousand mcg is 1 mg, so 0.1 mg moves the decimal one place too far, a tenfold underdose. One and a half teaspoons is 7.5 mL, and 22.5 mL uses the 15-mL tablespoon instead of the 5-mL teaspoon. Sixty-eight kg is 149.6 lb; 30.9 lb comes from dividing by 2.2 when kilograms must be multiplied.
Question 7 of 20
A 58-year-old client with low back pain reports taking 2 extra-strength acetaminophen 500-mg tablets at 0600, 1200, 1800 and 2400 over the past 24 hours, plus 2 tablets of hydrocodone-acetaminophen 5 mg/325 mg at 0300. How should the nurse interpret the client's acetaminophen intake?
- 4 g, which is at the daily maximum but still acceptable today
- 4.65 g, which exceeds the 4-g daily maximum and should be reported
- About 0.47 g, well under the daily limit, so no action is needed
- About 3.25 g, which is within the 4-g daily maximum for adults
Show the answer and rationale
Answer: B
Eight extra-strength tablets are 8 × 500 = 4,000 mg, and the 2 combination tablets add 2 × 325 = 650 mg, for 4,650 mg, or 4.65 g. That is above the 4,000-mg (4-g) adult maximum in 24 hours set by FDA, so the nurse reports it because of the risk of liver injury. Stopping at 4 g, the most tempting answer, misses the acetaminophen hidden in the opioid combination product. Counting each tablet as 325 mg gives 3.25 g, and moving the decimal four places instead of three gives 0.47 g.
Question 8 of 20
Digoxin 35 mcg PO is prescribed for an infant with heart failure. The pediatric elixir contains 0.05 mg/mL, and the infant's apical pulse is 128 beats/min. How many mL should the nurse give?
- 3.5 mL
- 0.35 mL
- 1.4 mL
- 0.7 mL
Show the answer and rationale
Answer: D
Convert so the units match: 0.05 mg/mL is 50 mcg/mL, and 35 mcg ÷ 50 mcg × 1 mL = 0.7 mL, measured in a calibrated oral syringe. An apical pulse of 128 beats/min is above the usual infant hold parameter of about 90 to 110 beats/min, so the dose can be given. The runner-up is 1.4 mL, the result of doubling the dose when the ratio is set up carelessly, which would give 70 mcg. A volume of 0.35 mL delivers only half the dose, 17.5 mcg, and 3.5 mL is a fivefold overdose from a misplaced decimal, an especially dangerous error with a drug as potent as digoxin.
Question 9 of 20
A 4-year-old is to receive 150 mL of 0.9% sodium chloride over 90 minutes by gravity through a volume-control chamber with microdrip tubing (60 gtt/mL). How many drops per minute should the nurse regulate?
- 25 gtt/min
- 150 gtt/min
- 100 gtt/min
- 2 gtt/min
Show the answer and rationale
Answer: C
(150 mL × 60 gtt/mL) ÷ 90 min = 100 gtt/min; with a microdrip set, drops per minute equal mL/hr, and 150 mL over 1.5 hours is 100 mL/hr. 150 gtt/min is the runner-up, a misuse of that shortcut that treats the total volume as the hourly rate, so the fluid would finish in 1 hour. 25 gtt/min uses a 15 gtt/mL macrodrip factor, and 2 gtt/min is the mL per minute without the drop factor. Filling the chamber with only a limited volume at a time protects a small child from accidental fluid overload.
Question 10 of 20
A child who weighs 33 lb is prescribed cefazolin IV every 8 hours for a mild skin infection. The drug reference lists 25 to 50 mg/kg/day divided into 3 or 4 equal doses. What is the safe range for each dose?
- 93.8 to 187.5 mg
- 125 to 250 mg
- 275 to 550 mg
- 375 to 750 mg
Show the answer and rationale
Answer: B
Convert the weight, 33 lb ÷ 2.2 = 15 kg, multiply both ends of the range, 25 × 15 = 375 mg and 50 × 15 = 750 mg per day, then divide by the 3 doses that every 8 hours gives: 125 to 250 mg per dose. 375 to 750 mg is the runner-up, the correct daily range compared directly with a single dose, which would let a triple dose pass. 93.8 to 187.5 mg divides by 4, the reference's every-6-hour option rather than the prescribed schedule, and 275 to 550 mg uses the weight in pounds.
A timed or tutor-mode set in the app, scored by area, with every miss saved for review. Free, no sign-up needed.
Question 11 of 20
After the rapid loading dose, amiodarone 1 mg/min IV for the next 6 hours is prescribed for a client with recurrent ventricular tachycardia. The premixed bag contains 360 mg in 200 mL of dextrose 5% in water. At what rate should the nurse set the pump? (Round to the nearest tenth.)
- 60 mL/hr
- 0.6 mL/hr
- 108 mL/hr
- 33.3 mL/hr
Show the answer and rationale
Answer: D
The prescription is per minute but the pump runs per hour: 1 mg/min × 60 = 60 mg/hr, and the bag holds 360 ÷ 200 = 1.8 mg/mL, so 60 ÷ 1.8 = 33.3 mL/hr, the label's 0.556 mL/min. 60 mL/hr is the most tempting error, the right hourly dose with mg mistaken for mL, which would deliver 1.8 mg/min. 0.6 mL/hr leaves out the 60 minutes, and 108 mL/hr multiplies by the concentration instead of dividing. After 6 hours the dose drops to 0.5 mg/min, or 16.7 mL/hr.
Question 12 of 20
A client in the postanesthesia care unit has a prescription for fentanyl 25 mcg IV now for incisional pain. The vial is labeled fentanyl citrate 0.05 mg/mL. How many mL should the nurse draw up?
- 5 mL
- 0.05 mL
- 2 mL
- 0.5 mL
Show the answer and rationale
Answer: D
Convert the label to the units of the order: 0.05 mg × 1,000 = 50 mcg/mL, and 25 mcg ÷ 50 mcg/mL = 0.5 mL, measured in a 1-mL syringe. Inverting the ratio, 50 ÷ 25, gives 2 mL, four times the dose, a common slip. Reading 0.05 mg as 5 mcg gives 5 mL, a tenfold overdose of a high-alert opioid, and reading it as 500 mcg gives 0.05 mL. Writing the conversion out before dividing prevents all three.
Question 13 of 20
A client with type 2 diabetes has prescriptions for insulin lispro 6 units subcutaneously with meals plus a lispro correction scale for the premeal glucose: 150 to 199 mg/dL, 1 unit; 200 to 249 mg/dL, 2 units; 250 to 299 mg/dL, 3 units; 300 to 349 mg/dL, 4 units; 350 mg/dL or higher, call the provider. The lunch tray has arrived, and the premeal glucose is 250 mg/dL. How many units of insulin lispro should the nurse give?
- 6 units
- 8 units
- 9 units
- 3 units
Show the answer and rationale
Answer: C
The mealtime dose and the correction dose are added: a glucose of 250 mg/dL falls in the 250-to-299 row, so 6 units + 3 units = 9 units, measured in a U-100 insulin syringe or dialed on a pen. Using the 200-to-249 row gives 8 units, the most tempting error because 250 sits on the boundary between rows. Giving only the 3-unit correction leaves the meal uncovered, and giving only the 6-unit mealtime dose ignores the high premeal glucose.
Question 14 of 20 · Select all that apply
The nurse is checking IV prescriptions for several children and a neonate against the drug reference ranges shown in parentheses. Which prescriptions can the nurse give as written? Select all that apply.
- A child who weighs 44 lb: vancomycin 440 mg IV every 6 hours (10 mg/kg per dose)
- A child who weighs 66 lb: ondansetron 4 mg IV before surgery (0.1 mg/kg for a child 40 kg or less)
- A neonate who weighs 1,500 g: caffeine citrate 30 mg IV as a loading dose (20 mg/kg)
- A child who weighs 26.4 lb: acyclovir 120 mg IV every 8 hours (10 mg/kg per dose)
- A child who weighs 22 lb: cefazolin 125 mg IV every 6 hours (25 to 50 mg/kg/day in 3 or 4 divided doses)
- A child who weighs 39.6 lb: ceftriaxone 900 mg IV every 12 hours (50 to 75 mg/kg/day in 2 divided doses)
Show the answer and rationale
Answer: C, D, E
The 22-lb child weighs 10 kg, so cefazolin 125 mg every 6 hours is 500 mg/day, or 50 mg/kg/day; the 26.4-lb child weighs 12 kg, so acyclovir 120 mg is exactly 10 mg/kg; and the 1,500-g neonate weighs 1.5 kg, so 30 mg of caffeine citrate is 20 mg/kg. Vancomycin 440 mg uses the weight in pounds: the 44-lb child weighs 20 kg and needs 200 mg. Ondansetron 4 mg is the dose for children over 40 kg, but the 66-lb child weighs 30 kg and needs 3 mg. Ceftriaxone 900 mg looks right because it is 50 mg/kg, but that is per dose; every 12 hours makes 1,800 mg/day, or 100 mg/kg/day, above the 75 mg/kg/day maximum. Doses outside the range are held and clarified.
Question 15 of 20
A client's 0.9% sodium chloride is prescribed at 125 mL/hr by gravity. The tubing's drop factor is 15 gtt/mL, and the nurse counts 25 drops in 1 minute. At what rate in mL/hr is the solution actually infusing?
- 375 mL/hr
- 100 mL/hr
- 6.3 mL/hr
- 25 mL/hr
Show the answer and rationale
Answer: B
Divide the drops by the drop factor, then multiply by 60 minutes: 25 ÷ 15 = 1.67 mL/min × 60 = 100 mL/hr, so the infusion is behind and the nurse checks the line and adjusts it to (125 × 15) ÷ 60 = 31 gtt/min. 25 mL/hr is the tempting error, because drops per minute equal mL/hr only with a 60 gtt/mL microdrip set. 6.3 mL/hr runs the drops-per-minute formula backward, and 375 mL/hr multiplies the drops by the drop factor instead of dividing.
Question 16 of 20
A child who weighs 50.6 lb is prescribed vancomycin 40 mg/kg/day IV divided every 6 hours. The reconstituted vial contains 50 mg/mL. How many mL should the nurse draw up for each dose before it is further diluted for infusion? (Round to the nearest tenth.)
- 18.4 mL
- 4.6 mL
- 6.1 mL
- 10.1 mL
Show the answer and rationale
Answer: B
Convert the weight, 50.6 lb ÷ 2.2 = 23 kg; the daily dose is 40 mg × 23 = 920 mg, and every 6 hours means 4 doses, so each dose is 230 mg, matching the label's usual 10 mg/kg every 6 hours; 230 ÷ 50 = 4.6 mL. 6.1 mL is the runner-up: dividing by 3 is the habit from every-8-hour drugs. 10.1 mL uses the weight in pounds, and 18.4 mL is the whole day's dose in one syringe. Each dose is then diluted and infused over at least 60 minutes.
Question 17 of 20
Dopamine 5 mcg/kg/min IV is prescribed for a client with symptomatic hypotension who weighs 165 lb. The bag contains 400 mg in 250 mL of dextrose 5% in water. At handoff, the nurse finds the pump running at 30.9 mL/hr. Which action should the nurse take?
- Reduce the rate to 14.1 mL/hr, then assess the client and report the error
- Keep the rate, because 30.9 mL/hr delivers exactly 5 mcg/kg/min for this client
- Stop the infusion and notify the provider before making any change
- Keep the rate until the pharmacist confirms the calculation
Show the answer and rationale
Answer: A
The client weighs 165 ÷ 2.2 = 75 kg: 5 mcg × 75 = 375 mcg/min, × 60 = 22,500 mcg/hr, and 400 mg in 250 mL is 1,600 mcg/mL, so the correct rate is 14.1 mL/hr. 30.9 mL/hr is what the formula gives with the weight in pounds, more than twice the prescribed dose. The nurse corrects the pump at once, checks the blood pressure, heart rate and rhythm, notifies the provider and files an event report. Stopping the infusion is the runner-up, but the prescription is clear and the client depends on the drug, so an abrupt stop can drop the pressure. Waiting for the pharmacist leaves the overdose running.
Question 18 of 20
A client with type 1 diabetes is diaphoretic and confused, cannot swallow safely, and has a fingerstick glucose of 42 mg/dL. The hypoglycemia protocol prescribes dextrose 50% 12.5 g IV push. The prefilled syringe contains dextrose 50%, 25 g in 50 mL. How many mL should the nurse give?
- 50 mL
- 6.3 mL
- 25 mL
- 12.5 mL
Show the answer and rationale
Answer: C
A 50% solution holds 50 g in every 100 mL, or 0.5 g/mL, which matches the label of 25 g in 50 mL; 12.5 g ÷ 0.5 g/mL = 25 mL, half the syringe. Giving 12.5 mL, the most tempting error, assumes 1 g in each mL and delivers only 6.25 g, and 6.3 mL comes from multiplying 12.5 by 0.5 instead of dividing. The full 50 mL is the 25-g dose, twice what the protocol prescribes. After the dose, the nurse rechecks the glucose as the protocol directs.
Question 19 of 20
A client with type 2 diabetes and severe insulin resistance takes insulin regular U-500, 150 units subcutaneously before breakfast. The pharmacy has dispensed a U-500 vial, and the medication room stocks U-500 insulin syringes, U-100 insulin syringes and 1-mL tuberculin syringes. How should the nurse measure the dose?
- Draw up 1.5 mL, as if it were U-100 insulin
- Draw up 0.3 mL of the U-500 insulin in a 1-mL tuberculin syringe
- Draw up to the 30-unit mark on a U-100 insulin syringe
- Draw up to the 150-unit mark on a U-500 insulin syringe
Show the answer and rationale
Answer: D
The FDA-approved U-500 syringe is marked in units of U-500 insulin, so the nurse draws to the 150-unit mark with no conversion; FDA advises using only the U-500 syringe with the U-500 vial and not switching syringe types. Drawing to 30 units on a U-100 syringe or 0.3 mL in a tuberculin syringe measures the right volume, which makes both tempting, but FDA removed those conversions from the vial label once the dedicated syringe was approved, and switching syringe types raises the risk of dosing errors. Treating U-500 as U-100 insulin gives 1.5 mL, or 750 units, five times the dose.
Question 20 of 20
Vancomycin 1,500 mg in 300 mL of 0.9% sodium chloride is prescribed for an adult client with a methicillin-resistant Staphylococcus aureus bloodstream infection. The label says to give each dose at no more than 10 mg/min or over at least 60 minutes, whichever is longer. What is the fastest rate the nurse may program on the pump?
- 300 mL/hr
- 600 mL/hr
- 200 mL/hr
- 120 mL/hr
Show the answer and rationale
Answer: D
At 10 mg/min, 1,500 mg takes 150 minutes, which is longer than 60, so the longer time applies: 300 mL ÷ 2.5 hours = 120 mL/hr, the same as 600 mg/hr ÷ 5 mg/mL. 300 mL/hr is the runner-up because 60 minutes is the familiar vancomycin time, but for a dose this large it runs at 25 mg/min and raises the risk of an infusion reaction with flushing and hypotension. 200 mL/hr reads 150 minutes as 1.5 hours, and 600 mL/hr is the hourly dose in mg mistaken for mL.
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