NCLEX Lab Values You Must Memorize (2026 Cheat Sheet)

You cannot memorize every lab on the planet, and the NCLEX does not expect you to. It expects you to know a short list of high-yield values cold, and to know what to do when one is off. Here is that list, with the nursing reason behind each, built for the 2026 exam.

One note before we start: reference ranges vary slightly by lab and source. Learn the standard ranges below, but always defer to the values your program or facility uses.

Electrolytes

• Sodium: 135 to 145 mEq/L. Think neuro. Too low or too high and you watch for confusion and seizures.
• Potassium: 3.5 to 5.0 mEq/L. Think heart. Both low and high potassium cause dangerous dysrhythmias. This is a big one.
• Calcium: 9.0 to 10.5 mg/dL. Think muscles and nerves. Watch Chvostek and Trousseau signs when it is low.
• Magnesium: 1.3 to 2.1 mEq/L. The quiet one. Low magnesium often rides along with low potassium and low calcium.

Renal and metabolic

• BUN: 10 to 20 mg/dL.
• Creatinine: 0.6 to 1.2 mg/dL. The better marker of kidney function. Rising creatinine is a red flag.
• Fasting glucose: 70 to 100 mg/dL.
• Hemoglobin A1c: below 5.7% is normal; 6.5% or higher indicates diabetes.

Hematology

• Hemoglobin: roughly 12 to 18 g/dL depending on sex.
• Hematocrit: about three times the hemoglobin.
• WBC: 5,000 to 10,000. Low means infection risk and neutropenic precautions.
• Platelets: 150,000 to 400,000. Below 50,000 means bleeding precautions.

Coagulation

• INR: 0.8 to 1.1 normal; therapeutic on warfarin is 2 to 3.
• aPTT: 30 to 40 seconds; therapeutic on heparin is 1.5 to 2.5 times normal.

The values that kill: memorize these first

If you are short on time, burn these in, because they drive immediate action on the NCLEX: potassium, sodium, glucose, WBC, platelets, INR, and aPTT. When one of these is off, the exam usually wants a specific nursing action, not just recognition.

How to actually remember them

Do not just stare at a chart. Turn each value into an if-then: "If potassium is high, then I think cardiac monitor and I do not give more potassium." Then do practice questions that force the action. Recognition plus action is what earns the point.

Get the full high-yield set

Our 2026 NCLEX Ultimate Mastery Notes lay out the must-know lab values with the nursing actions attached, alongside the rest of the high-yield content, for $33.15. Short on time? The 2026 Crash Course Notes give you the condensed version for $11.90. Both come with our Pass Guarantee.

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Frequently asked questions

What lab values are most important for the NCLEX?
Potassium, sodium, glucose, WBC, platelets, INR, and aPTT are the highest-yield because they trigger specific nursing actions.

Do I need exact numbers?
Know the standard ranges, but focus on what to do when a value is abnormal. The NCLEX tests action more than recall.

Are lab ranges the same everywhere?
They vary slightly by lab and source. Learn the common ranges and defer to your program's values.

You've got this. Learn the number, then learn the move.

Nurse June, BSN, RN
Founder, Your Nursing Space