NCLEX-RN Guide

NCLEX Lab Values to Memorize: Categorized Normal Ranges

Complete list of NCLEX lab values to memorize — electrolytes, ABGs, haematology, coagulation, renal, hepatic, cardiac and therapeutic drug levels, with NGN context.

Quick Answer

The NCLEX lab values worth memorizing are electrolytes, ABGs, CBC, coagulation studies, renal and hepatic panels, cardiac markers, glucose/HbA1c and therapeutic drug levels. Learn each value's normal range plus the one nursing action triggered when it is abnormal — Next Gen items give you the value and ask what you do.

Lab values appear on every NCLEX-RN form, and the Next Generation NCLEX has made them more important, not less. NGN case studies hand you a full lab panel inside an electronic health record tab and expect you to decide which values are relevant, which are dangerous, and what to do first. Recognizing an abnormal value is no longer enough — you must link it to a nursing action. Every range on this page is grouped by system so it is memorized as a pattern, and each block ends with the action the exam is really testing.

📌 Key Takeaways

✓Memorize ranges in categories (electrolytes, ABGs, CBC, coagulation, renal, hepatic, cardiac) rather than as an alphabetical list
✓For every value, learn one trigger action — NGN items test the response, not the number
✓Critical values (K⁺ <2.5 or >6.5, glucose <54, platelets <20,000, INR >5) must be recognized instantly
✓ABG interpretation follows ROME: Respiratory Opposite, Metabolic Equal
✓Therapeutic drug levels (digoxin, lithium, phenytoin, vancomycin, theophylline) are frequent, easy points

Electrolytes — The Most Tested Lab Group on the NCLEX

If you memorize only one table, memorize this one. Electrolyte disturbances drive cardiac, neurologic and renal questions across every content area.

Serum electrolytes: range, danger sign, nursing action
Lab	Normal range	Key sign when abnormal	Priority nursing action
Sodium (Na⁺)	135–145 mEq/L	Low: confusion, seizures. High: thirst, dry mucosa	Seizure precautions; correct slowly to avoid cerebral shifts
Potassium (K⁺)	3.5–5.0 mEq/L	Dysrhythmias, peaked T waves (high), flat T/U waves (low)	Cardiac monitoring; never IV push potassium
Calcium (Ca²⁺)	9.0–10.5 mg/dL	Low: Chvostek/Trousseau, tetany. High: lethargy, stones	Seizure and fall precautions; check magnesium too
Magnesium (Mg²⁺)	1.3–2.1 mEq/L	Low: tremors, torsades. High: loss of deep tendon reflexes	Check DTRs before each dose of magnesium
Phosphorus	3.0–4.5 mg/dL	Inverse relationship with calcium	Assess for muscle weakness; review renal function
Chloride	97–107 mEq/L	Moves with sodium; affects acid–base	Interpret alongside ABGs

Arterial Blood Gases and the ROME Method

ABG questions are algorithmic. Learn the four numbers, then apply ROME: in Respiratory disorders pH and CO₂ move in Opposite directions; in Metabolic disorders pH and bicarbonate move Equally (same direction).

ABG normal values
Value	Normal range	Interpretation clue
pH	7.35–7.45	<7.35 acidosis, >7.45 alkalosis
PaCO₂	35–45 mmHg	Respiratory component — lungs
HCO₃⁻	22–26 mEq/L	Metabolic component — kidneys
PaO₂	80–100 mmHg	Oxygenation status
SaO₂	95–100%	Haemoglobin saturation
Base excess	−2 to +2 mEq/L	Degree of metabolic derangement

•Respiratory acidosis: hypoventilation — COPD, opioid overdose, atelectasis
•Respiratory alkalosis: hyperventilation — anxiety, pain, early sepsis, high altitude
•Metabolic acidosis: DKA, renal failure, diarrhoea, shock (lactic acid)
•Metabolic alkalosis: vomiting, nasogastric suction, excess antacids, diuretics

Haematology and Coagulation

CBC and coagulation values drive bleeding-precaution, infection and transfusion questions. Note the antidotes — they are commonly asked in the same item.

CBC and clotting studies
Lab	Normal range	Exam-critical point
WBC	5,000–10,000/mm³	<1,000 neutrophils = neutropenic precautions
RBC	4.2–6.1 million/mm³	Low in anaemia and chronic kidney disease
Haemoglobin	12–18 g/dL (F 12–16, M 14–18)	<7 g/dL commonly triggers transfusion
Haematocrit	37–52% (roughly 3× Hgb)	Rises with dehydration
Platelets	150,000–400,000/mm³	<50,000 bleeding risk; <20,000 spontaneous bleeding
PT	11–12.5 seconds	Monitors warfarin
INR	0.8–1.1 (therapeutic 2–3 on warfarin)	Antidote: vitamin K
aPTT	30–40 sec (therapeutic 1.5–2.5×)	Monitors heparin; antidote protamine sulfate
D-dimer	<0.5 mcg/mL	Elevated in PE, DVT, DIC

Renal, Hepatic, Cardiac and Metabolic Panels

These panels appear constantly in NGN case studies where you must sift relevant from irrelevant findings.

Organ-system laboratory values
Lab	Normal range	What it tells you
BUN	10–20 mg/dL	Rises with dehydration, GI bleed, renal impairment
Creatinine	0.6–1.2 mg/dL	Most specific marker of renal function
GFR	>90 mL/min	<60 for 3 months = chronic kidney disease
Albumin	3.5–5.0 g/dL	Nutrition and oncotic pressure; low = oedema
Total bilirubin	0.3–1.0 mg/dL	Elevated = jaundice, hepatic or biliary disease
ALT / AST	ALT 4–36 U/L; AST 0–35 U/L	Hepatocellular injury; monitor with statins
Ammonia	15–45 mcg/dL	High in hepatic encephalopathy — give lactulose
Troponin I	<0.03 ng/mL	Most specific marker of myocardial infarction
BNP	<100 pg/mL	>100 suggests heart failure
Fasting glucose	70–110 mg/dL	<54 severe hypoglycaemia — treat immediately
HbA1c	<5.7% (diabetic goal <7%)	3-month glycaemic control
Total cholesterol	<200 mg/dL	LDL <100, HDL >40–60

Therapeutic Drug Levels

Narrow-therapeutic-index drugs are guaranteed pharmacology points because the exam can pair a level with a toxicity picture.

Therapeutic ranges and toxicity signs
Drug	Therapeutic level	Toxicity presentation
Digoxin	0.5–2.0 ng/mL	Nausea, visual halos, bradycardia, dysrhythmias
Lithium	0.6–1.2 mEq/L	Tremor, diarrhoea, ataxia, confusion; worsens with low sodium
Phenytoin	10–20 mcg/mL	Nystagmus, ataxia, gingival hyperplasia
Vancomycin (trough)	10–20 mcg/mL	Nephrotoxicity, ototoxicity
Theophylline	10–20 mcg/mL	Tachycardia, restlessness, seizures
Carbamazepine	5–12 mcg/mL	Bone marrow suppression, ataxia
Magnesium (obstetric)	4–7 mEq/L	Loss of DTRs, respiratory depression; antidote calcium gluconate

Lab Values in Next Generation NCLEX (NGN) Items

In NGN case studies, labs arrive inside an EHR-style tab beside nurses' notes and vital signs. The clinical judgment model asks you to Recognize Cues (which values are abnormal and relevant), Analyze Cues (what condition they point to), Prioritize Hypotheses, Generate Solutions, Take Action, and Evaluate Outcomes. A potassium of 6.8 mEq/L is not the answer — the answer is placing the patient on a cardiac monitor and holding the ordered potassium supplement.

Practise this way: whenever you meet an abnormal value in a question, say the trigger action out loud before you look at the options. Over a few hundred questions this becomes automatic, and the lab tab in an NGN case study stops being overwhelming.

•Recognize cues: scan for values outside the range you memorized
•Analyze cues: cluster abnormal values into one likely problem rather than treating each in isolation
•Take action: pick the nursing intervention you can perform now, not the provider call
•Evaluate outcomes: re-check the same value or the sign it produced

Test your lab value recall right now

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Frequently Asked Questions

What lab values do I need to memorize for the NCLEX?

Prioritize electrolytes (sodium, potassium, calcium, magnesium), ABGs, CBC, coagulation studies (PT/INR, aPTT), renal values (BUN, creatinine, GFR), hepatic values (ALT, AST, ammonia, albumin), cardiac markers (troponin, BNP), glucose/HbA1c, and therapeutic drug levels for digoxin, lithium, phenytoin, vancomycin and theophylline.

Are lab value ranges given to you on the NCLEX?

No. The NCLEX-RN does not supply a reference table, so any value shown in a stem must be interpreted from memory. This is why lab ranges are among the highest-return memorization items in your entire study plan.

How do I memorize NCLEX lab values quickly?

Group them by system, learn the boundary numbers rather than the midpoints, attach one trigger action to each value, and use write-cover-check with spaced repetition at 24 hours, 3 days and 7 days. Then apply them immediately in practice questions so they are stored in a clinical context.

Which lab values are considered critical on the NCLEX?

Commonly tested critical values include potassium below 2.5 or above 6.5 mEq/L, sodium below 120 or above 160 mEq/L, glucose below 54 mg/dL, platelets below 20,000/mm³, haemoglobin below 7 g/dL, INR above 5, and pH below 7.20 or above 7.60. Each requires immediate action, not observation.

Do NGN case studies test lab values differently?

Yes. NGN items embed labs in an EHR tab and ask you to select relevant cues, link them to a hypothesis, and choose actions. You must filter irrelevant normal values as well as identify abnormal ones, so practise with full case studies rather than isolated recall drills.

📚 Related NCLEX Resources

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