Lab Values for Nurses: practice problems and exam questions

The laboratory results nurses read every shift: typical adult reference ranges, sodium, potassium, calcium, magnesium and phosphate imbalances, the blood count, clotting tests for warfarin and heparin, kidney and liver tests, glucose and HbA1c, cardiac markers, therapeutic drug levels and arterial blood gases.

Practise this course for freePractise this courseTake a mock exam5 free problems every day. No card needed.

Cram pack (PDF)Formula sheets, method steps and practice problems with full solutions, ready to print.

Topics in this course

  1. Lab values & electrolyteskey terms and facts · applying the concepts · cases and analysismultiple choice
  2. Arterial blood gas interpretationacid–base classification · compensation and expected values · mixed disorders and gas exchangecalculations
  3. Clinical pharmacokineticshalf-life, levels and loading doses · clearance, Vd, S and F · regimen design and renal adjustmentcalculations
  4. Clinical nursingkey terms and facts · applying the concepts · cases and analysismultiple choice

Exam tips for Lab Values for Nurses

  • Learn the typical ranges, but always read a result against the range of the laboratory that ran it.
  • Look at the patient and the trend before the single number, and think about how the sample was taken.
  • Link each imbalance to its signs and its first nursing action, such as holding digoxin when potassium is low.

Worked examples

Lab values & electrolytesEasy

Which drug commonly causes a low serum potassium?

  1. AFurosemide
  2. BAmiloride
  3. CLisinopril
  4. DSpironolactone
Show hints
  1. Some diuretics waste potassium in the urine; others spare it.
  2. Two wrong answers are now crossed out. One of the remaining two is right.
Show the answer and explanation

Why this is the answer

Loop and thiazide diuretics increase potassium loss in the urine and commonly cause hypokalemia. Spironolactone and amiloride are potassium-sparing, and ACE inhibitors such as lisinopril tend to raise potassium.

Answer

A · Furosemide
Arterial blood gas interpretationMedium

Practice values: Na⁺ 151 mmol/L, glucose 17.6 mmol/L and urea 22.7 mmol/L. Calculate the serum osmolality Osm = 2·Na⁺ + glucose + urea to the nearest whole number.

Na⁺ 151 mmol/Lglucose 17.6 mmol/Lurea 22.7 mmol/L

Find Osm (mOsm/kg)

Show hints
  1. Sodium and its anions make most of the osmolality: 2·Na⁺.
  2. Add glucose and urea as they are; all values are in mmol/L.
  3. 2·151 = 302.
Show the answer and the step-by-step solution

Derived values: calculated serum osmolality is 2·Na⁺ + glucose + urea with all values in mmol/L (2·Na⁺ + glucose/18 + BUN/2.8 with glucose and BUN in mg/dL); normal is about 275–295 mOsm/kg. The P/F ratio is PaO₂ divided by FiO₂ as a fraction. The alveolar oxygen pressure is PAO₂ = FiO₂·(760 − 47) − PaCO₂/0.8 mmHg at sea level, and the A–a gradient is PAO₂ − PaO₂.

Calculated osmolality

Osm = 2·151 + 17.6 + 22.7 = 342.3 ≈ 342 mOsm/kg

Answer

Osm = 342 mOsm/kg

How practising works

  • “Practise this course” mixes problems from all its topics, like a real exam.
  • Every problem has new values, so you learn the method instead of an answer.
  • Stuck? Open a small hint first, and the full explanation only when you need it.
  • Mock exams are timed and have no hints, and you get your score and a full review at the end.

Calculators for this course

Loading dose and maintenance dose calculator (pharmacokinetics)Anion gap calculator (albumin-corrected, delta ratio)

Related courses

Nursing Fundamentals and Clinical PracticeMedical-Surgical NursingNCLEX-style practice questions (RN)NCLEX-style Prioritization & DelegationNCLEX-PN-style practice questions (LPN/LVN)Health AssessmentRespiratory Care and Oxygen TherapyPharmacy Calculations
Practise this course for freePractise this courseTake a mock exam5 free problems every day. No card needed.