Normal serum sodium range?

135–145 mEq/L. Below 135 is hyponatremia; above 145 is hypernatremia.

Normal serum potassium range?

3.5–5.0 mEq/L. Both hypokalemia and hyperkalemia cause cardiac dysrhythmias, so any potassium abnormality calls for cardiac monitoring.

At what serum potassium levels is the value considered critical?

Below 2.5 mEq/L or above 6.5 mEq/L. Either extreme is life-threatening because of the risk of cardiac arrest.

Normal serum chloride range?

98–106 mEq/L. Chloride generally moves in the same direction as sodium.

Normal total serum calcium range?

9.0–10.5 mg/dL. Low calcium produces tetany with positive Chvostek and Trousseau signs.

Normal serum magnesium range?

1.3–2.1 mEq/L (equivalently 1.6–2.6 mg/dL — check which unit the question uses). Low magnesium causes hyperactive reflexes and dysrhythmias; high magnesium depresses deep tendon reflexes and respirations.

Normal serum phosphorus range?

3.0–4.5 mg/dL. Phosphorus moves inversely to calcium, so a high phosphorus usually accompanies a low calcium.

Normal blood urea nitrogen (BUN) range?

10–20 mg/dL. BUN rises with kidney impairment but also with dehydration, GI bleeding, and a high-protein intake.

Normal serum creatinine range?

0.6–1.2 mg/dL. Creatinine is the more specific indicator of kidney function because it depends mainly on muscle mass rather than on protein intake or GI bleeding. Dehydration raises both, but BUN rises disproportionately — a BUN:creatinine ratio above 20:1 points to a prerenal cause.

Normal fasting blood glucose range?

70–110 mg/dL is the range NCLEX uses. Below 70 mg/dL is hypoglycemia and is treated first, because the brain has no glucose reserve. For diagnosis, the ADA uses a fasting glucose of 100–125 mg/dL for prediabetes and 126 mg/dL or higher for diabetes.

What HbA1c value is diagnostic of diabetes?

6.5% or higher. Below 5.7% is normal and 5.7–6.4% indicates prediabetes. HbA1c reflects average blood glucose over roughly the previous three months.

Normal white blood cell (WBC) count?

5,000–10,000/mm³. A falling count signals neutropenia risk and the need for protective precautions; a rising count suggests infection.

Normal hemoglobin range for adult males and females?

Males 14–18 g/dL; females 12–16 g/dL.

Normal hematocrit range for adult males and females?

Males 42–52%; females 37–47%. Hematocrit runs at roughly three times the hemoglobin value.

Normal platelet count?

150,000–400,000/mm³. Below 150,000 is thrombocytopenia, and bleeding precautions are standard once the count falls below 50,000.

Normal arterial blood pH?

7.35–7.45. Below 7.35 is acidosis; above 7.45 is alkalosis.

Normal PaCO2 on an arterial blood gas?

35–45 mmHg. PaCO2 is the respiratory component: it rises in respiratory acidosis and falls in respiratory alkalosis.

Normal serum bicarbonate (HCO3) on an arterial blood gas?

22–26 mEq/L. Bicarbonate is the metabolic component: it falls in metabolic acidosis and rises in metabolic alkalosis.

Normal PaO2 on an arterial blood gas?

80–100 mmHg. PaO2 measures oxygen dissolved in arterial blood, unlike SaO2, which measures hemoglobin saturation and is normally 95–100%.

Normal prothrombin time (PT)?

About 11–12.5 seconds (labs report 9.5–13 depending on reagent, so always compare with the reported control). PT evaluates the extrinsic pathway and is the basis of the INR used to monitor warfarin.

Therapeutic INR range for a client on warfarin?

2.0–3.0 for most indications. Without anticoagulation a normal INR is about 0.8–1.1. Vitamin K is the antidote for warfarin.

Normal activated partial thromboplastin time (aPTT), and the therapeutic goal on heparin?

Normal aPTT is 30–40 seconds. On therapeutic heparin the goal is 1.5 to 2.5 times the normal value.

What are the antidotes for heparin and for warfarin?

Protamine sulfate reverses heparin; vitamin K (phytonadione) reverses warfarin. Heparin is monitored by aPTT, warfarin by PT/INR.

Normal serum albumin range?

3.4–5.0 g/dL. Low albumin reflects poor nutritional status or liver disease and contributes to edema by lowering plasma oncotic pressure.

Normal total serum bilirubin range?

0.3–1.0 mg/dL. Bilirubin rises in liver disease and biliary obstruction, and jaundice appears as levels climb.

Therapeutic serum digoxin level, and the level considered toxic?

Therapeutic is 0.5–2.0 ng/mL; above 2.0 ng/mL is toxic. Hypokalemia increases the risk of digoxin toxicity, whose early signs include nausea, anorexia, and visual disturbances.

Therapeutic serum lithium level, and the level considered toxic?

Therapeutic is 0.6–1.2 mEq/L; above 1.5 mEq/L is toxic. Dehydration and low sodium intake raise lithium levels.

27 free flashcards

NCLEX Lab Values flashcards

This deck covers the laboratory values NCLEX questions assume you already know: the major electrolytes (sodium, potassium, chloride, calcium, magnesium, phosphorus), the complete blood count, arterial blood gases, coagulation studies, renal and hepatic markers, glucose and HbA1c, and the therapeutic ranges for digoxin and lithium. Every range is given in the standard US units used on the exam, so you memorize the number and the unit together.

Lab values show up on the NCLEX indirectly far more often than they appear as a straight recall question. A stem hands you a potassium of 6.2 mEq/L or a pH of 7.28 and asks what you do first, which client you see first, or whether to hold a medication — and you cannot answer any of that until you know instantly whether the value is normal, high, or low. Committing the ranges to memory turns those items into simple prioritization questions instead of guesses.

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How to study this deck

Learn each value as number plus unit in one breath — mEq/L for sodium, potassium, chloride, magnesium and bicarbonate; mg/dL for calcium, phosphorus, BUN, creatinine and glucose. Mixing up units is what makes a correct number score zero on a fill-in-the-blank item.
Once you can recall a range, do a second pass asking 'what is the nursing action if this is high, and if it is low?' — hyperkalemia and hypokalemia, for example, both point to cardiac monitoring but to opposite treatments.
Drill the ABG values (pH, PaCO2, HCO3) as a set of three rather than one at a time, then practice classifying sample gases: respiratory versus metabolic is decided by whether PaCO2 or HCO3 moved in the same direction as the pH.

NCLEX Lab Values: FAQ

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

The core set is electrolytes (sodium, potassium, chloride, calcium, magnesium, phosphorus), the CBC (WBC, hemoglobin, hematocrit, platelets), ABGs, coagulation studies (PT, INR, aPTT), renal markers (BUN, creatinine), liver markers (albumin, bilirubin), and glucose. You should also know the therapeutic ranges for digoxin and lithium.

How do I memorize lab values fast?

Group them by panel rather than learning them alphabetically, and always rehearse the unit with the number. Active recall beats rereading a chart: cover the value, say it out loud, then check. Cram builds flashcards from your own notes with AI and schedules the reviews with spaced repetition so the ranges stay fresh through test day.

Are lab values on the Next Generation NCLEX?

Yes. The NGN case studies and unfolding items regularly include a lab report you have to interpret before choosing an action, so the values are tested through clinical judgment rather than as standalone recall questions.

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