The NCLEX Numbers Worth Memorizing
The cutoffs that decide answers: electrolyte ranges, drug levels, ANC, platelets, glucose, Apgar, GCS. Organized by system.
Most numbers on the NCLEX are context. These are the ones that ARE the answer. Cold, no hesitation.
Electrolytes
Sodium 135-145. Potassium 3.5-5.0. Calcium 8.5-10.5 (total). Magnesium 1.5-2.5. Phosphate 2.5-4.5. The two that kill: potassium outside roughly 3-6 is a critical value, and severe hyponatremia (<120) means seizures. Never IV push potassium.
Hematology
ANC below 500 = severe neutropenia, protective precautions, and any fever is an emergency. Platelets 150-400. Below 50K: procedure risk. Below 20K: spontaneous bleeding risk. Below 10K: transfuse. Hgb below 7 is the usual transfusion threshold (below 8 with cardiac disease).
Drug levels
Digoxin 0.5-2.0 ng/mL. Lithium 0.6-1.2 mEq/L; toxic above 1.5. Draw 12 hours after the last dose. Phenytoin 10-20 mcg/mL. Magnesium sulfate (OB) therapeutic 4-7 mEq/L; lost DTRs are the first toxicity sign, calcium gluconate is the antidote. Heparin: aPTT 60-80 seconds (1.5-2x control). Antidote protamine. Warfarin: INR 2-3 for most indications, 2.5-3.5 for mechanical valves. Antidote vitamin K.
Glucose and diabetes
Hypoglycemia: below 70, treat with 15 g fast carbs, recheck in 15 minutes. Fasting glucose 126 or higher = diabetes (confirmed on repeat). A1c 6.5 or higher = diabetes; treatment goal under 7% for most adults. DKA typically runs glucose above 250 with ketones and acidosis; HHS runs much higher, often above 600, without significant ketosis.
ABGs
pH 7.35-7.45. CO2 35-45. HCO3 22-26. That is the whole entry fee for every ABG question. Respiratory opposite, metabolic equal (ROME). Target SpO2 88-92% in COPD.
Neuro and maternal-newborn
GCS runs 3 to 15. GCS 8 or less: intubate. Apgar: 7-10 normal, 4-6 moderate distress, 0-3 severe, scored at 1 and 5 minutes. Fetal heart rate baseline 110-160.
Frequently asked
Do I need the exact lab ranges or just high/low?
The exact range for the big five electrolytes, glucose, and the drug levels. For everything else, knowing the direction and the critical extreme is enough.
What about tube colors and less-common levels?
Lower yield. Nail this list first. A missed potassium range costs you more than a missed vancomycin trough.
Best way to make these stick?
Retrieval, not rereading. Blank-page dump the list from memory twice a week and check it. The ones you keep missing go on flashcards.
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