Insulin Dosage Calculation Practice Problems for Nursing Students

Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — October 2026

By Ryan Mitchell · Worked examples for nursing and pharmacy exams

These are practice calculations, not dosing instructions. In clinical practice, follow the written order, your facility's protocol and its double-check policy.

The six formulas behind every insulin exam question

Insulin questions on nursing and pharmacy exams use a small set of formulas. Learn the six below, then work through the fifteen problems. Each answer shows every step, so you can find exactly where a mistake happens.

You needFormula
Volume to draw upmL = units ÷ concentration (units per mL)
Infusion pump ratemL/hr = units per hour ÷ units per mL in the bag
Weight-based rateunits/hr = dose (units/kg/hr) × weight (kg); kg = lb ÷ 2.2
Days a supply lastsdays = units in the vial or pen ÷ units used per day
Correction doseunits = (current glucose − target) ÷ correction factor
Meal doseunits = grams of carbohydrate ÷ carb ratio

Standard insulin is U-100, which means 100 units in every mL. Unless a question says otherwise, assume U-100.

Section 1: Converting insulin units to mL

Divide the dose by the concentration. For U-100 insulin, that simply moves the decimal point two places to the left. Our insulin units to mL calculator checks any value.

Problem 1

James is prescribed 20 units of U-100 regular insulin. How many mL do you draw up?

  1. Concentration is 100 units/mL.
  2. mL = 20 ÷ 100 = 0.2 mL.
  3. On a U-100 insulin syringe, draw to the 20-unit mark.

Answer: 0.2 mL

Problem 2

A pharmacy technician must add 40 units of U-100 insulin to an intravenous solution. How many mL are needed? (a) 0.3 mL (b) 0.4 mL (c) 0.5 mL (d) 0.6 mL

  1. mL = 40 ÷ 100.
  2. = 0.4 mL.

Answer: 0.4 mL (b)

Problem 3

A patient is prescribed 10 units of insulin. The vial contains 100 units/mL. How many mL do you draw up?

  1. mL = 10 ÷ 100.
  2. = 0.1 mL.

Answer: 0.1 mL

Problem 4

Tom has U-40 insulin (40 units in each mL) and needs a dose of 28 units. How many mL is drawn up?

  1. Concentration is 40 units/mL, not 100.
  2. mL = 28 ÷ 40 = 0.7 mL.
  3. Use a U-40 syringe and draw to the 28-unit mark. A U-100 syringe would give the wrong dose.

Answer: 0.7 mL

Problem 5

A U-100 syringe is filled to 0.15 mL. How many units does it hold?

  1. Units = mL × concentration.
  2. = 0.15 × 100 = 15 units.

Answer: 15 units

Section 2: IV insulin drip rates (units/hr and mL/hr)

First find how many units are in each mL of the bag. Then divide the ordered units per hour by that number. The insulin drip calculator runs the same two steps.

Problem 6

An insulin infusion contains 100 units of regular insulin in 100 mL of normal saline. The order is 4 units/hr. What is the rate in mL/hr?

  1. Bag concentration = 100 ÷ 100 = 1 unit/mL.
  2. mL/hr = 4 ÷ 1 = 4 mL/hr.

Answer: 4 mL/hr

Problem 7

A client receives regular insulin by continuous IV infusion at 10 units/hr. A total of 200 units has been added to 0.5 L of 0.9% NaCl. What is the hourly rate in mL/hr?

  1. Convert the bag volume: 0.5 L = 500 mL.
  2. Concentration = 200 ÷ 500 = 0.4 units/mL.
  3. mL/hr = 10 ÷ 0.4 = 25 mL/hr.

Answer: 25 mL/hr

Problem 8

A patient in diabetic ketoacidosis weighs 140 lb. The order is a Humulin R drip at 0.1 units/kg/hr. The bag contains 125 units in 250 mL. How many mL per hour do you set? (a) 12.7 mL/hr (b) 6.35 mL/hr (c) 0.79 mL/hr (d) 0.45 mL/hr

  1. Weight in kg = 140 ÷ 2.2 = 63.6 kg.
  2. Dose = 0.1 × 63.6 = 6.36 units/hr.
  3. Concentration = 125 ÷ 250 = 0.5 units/mL.
  4. mL/hr = 6.36 ÷ 0.5 = 12.7 mL/hr.

Answer: 12.7 mL/hr (a)

Problem 9

A patient weighing 80 kg is ordered insulin at 0.1 units/kg/hr from a bag of 100 units in 100 mL. Find the dose and the pump rate.

  1. Dose = 0.1 × 80 = 8 units/hr.
  2. Concentration = 1 unit/mL.
  3. mL/hr = 8 ÷ 1 = 8 mL/hr.

Answer: 8 units/hr at 8 mL/hr

Section 3: How long a vial or pen lasts

A standard 10 mL vial of U-100 insulin holds 1,000 units, and a 3 mL pen holds 300 units. Divide by the daily total to get days. Real supply runs out sooner than the arithmetic suggests, because most opened vials and pens are discarded after 28 days and pens use a priming dose. The insulin vial calculator includes both limits.

Problem 10

A patient is dispensed a 10 mL vial of insulin with a concentration of 100 units/mL. The patient takes 40 units in the morning and 10 units in the evening. How many days will this vial last?

  1. Units in the vial = 10 × 100 = 1,000 units.
  2. Daily use = 40 + 10 = 50 units.
  3. Days = 1,000 ÷ 50 = 20 days.
  4. This is within the 28-day in-use limit, so the vial is used up first.

Answer: 20 days

Problem 11

A patient is to receive 50 units of NPH insulin each day. How many days will a 10 mL vial of NPH (U-100) last?

  1. 1,000 units ÷ 50 units per day.
  2. = 20 days.

Answer: 20 days

Problem 12

A patient injects 40 units once a day using 3 mL U-100 pens. How many pens cover 90 days?

  1. Units needed = 40 × 90 = 3,600 units.
  2. Each pen holds 3 × 100 = 300 units.
  3. Pens = 3,600 ÷ 300 = 12 pens.
  4. In practice, add the 2-unit priming dose before each injection: 42 × 90 = 3,780 units, which needs 13 pens.

Answer: 12 pens (exam answer); 13 pens with priming

Section 4: Correction and mealtime doses

A correction dose brings a high reading back to target. A meal dose covers carbohydrate. When both apply, add them together. Our correction dose calculator works in mg/dL and mmol/L.

Problem 13

Richie's blood sugar is 220 mg/dL before lunch. His correction scale gives 1 additional unit for every 50 mg/dL over 120 mg/dL. How many correction units does he receive?

  1. Amount above target = 220 − 120 = 100 mg/dL.
  2. Units = 100 ÷ 50 = 2 units.

Answer: 2 units

Problem 14

A patient's glucose is 12.3 mmol/L. The target is 6.0 mmol/L and the correction factor is 2.5 mmol/L per unit. Calculate the correction dose.

  1. Amount above target = 12.3 − 6.0 = 6.3 mmol/L.
  2. Units = 6.3 ÷ 2.5 = 2.52 units.
  3. Round to what the pen can deliver: 2.5 units on a half-unit pen, 3 units on a whole-unit pen (or as the order directs).

Answer: 2.52 units, rounded to 2.5 units

Problem 15

A patient uses a carb ratio of 1 unit per 10 g. The meal contains 103 g of carbohydrate. Glucose is 180 mg/dL, the target is 120 mg/dL, and the correction factor is 30 mg/dL per unit. What is the total dose?

  1. Meal dose = 103 ÷ 10 = 10.3 units.
  2. Correction = (180 − 120) ÷ 30 = 2 units.
  3. Total = 10.3 + 2 = 12.3 units, rounded to 12 units on a whole-unit pen.

Answer: 12.3 units, given as 12 units To check your own answers, use the matching tools in our insulin calculation toolkit.

Rules examiners check on insulin questions

  • Write "units" in full. The Institute for Safe Medication Practices lists "U" and "IU" as error-prone abbreviations, because "U" is misread as 0 or 4.
  • Match the syringe to the insulin. U-100 syringes for U-100 insulin and U-40 syringes for U-40 insulin. Never draw U-500 insulin into a U-100 syringe.
  • Convert pounds to kilograms first. Divide by 2.2 before any weight-based step, and keep at least one decimal place until the end.
  • Round only at the last step, and only to what the device can measure: 1 unit on most pens, 0.5 units on half-unit pens and syringes.
  • Treat insulin as a high-alert medicine. Many hospitals require an independent double check of insulin doses and drip rates.

Frequently Asked Questions: Insulin Dosage Calculations

Divide the units by the concentration. For U-100 insulin, mL = units ÷ 100, so 20 units is 0.2 mL and 40 units is 0.4 mL. For U-40 insulin, divide by 40 instead: 28 units is 0.7 mL.

Find the bag concentration first by dividing total units by total mL. Then divide the ordered units per hour by that concentration. With 100 units in 100 mL (1 unit/mL), an order of 4 units/hr runs at 4 mL/hr.

A 10 mL vial of U-100 insulin holds 1,000 units. Divide 1,000 by the daily dose: at 50 units a day it lasts 20 days. Most opened vials are discarded after 28 days even if insulin is left.

Round only at the final step, to the nearest amount the pen or syringe can measure, unless the order states otherwise. Most pens deliver whole units; half-unit pens and syringes measure 0.5 units.

A handwritten "U" can be mistaken for a 0 or a 4, turning 10 U into 100 or 40. The Institute for Safe Medication Practices recommends writing the word "units" in full.

Sources

  1. Institute for Safe Medication Practices. List of Error-Prone Abbreviations, Symbols, and Dose Designations. Link
  2. Umpierrez GE et al. "Hyperglycemic Crises in Adults With Diabetes: A Consensus Report." Diabetes Care. 2024.
  3. American Diabetes Association. Standards of Care in Diabetes — 2026. Section 16 (Diabetes Care in the Hospital). Diabetes Care. 2026;49(Suppl 1). Link

Written by Ryan Mitchell · Last updated: October 2026

Units to mLAny concentration
Insulin DripUnits/hr to mL/hr
DKA Insulin0.1 units/kg/hr protocol
Carb RatioMeal dose from carbs