Lab Values Quick Reference
The typical adult ranges most tested on the NCLEX-RN, with what an abnormal result means for your client. For explanations and practice questions, see the full NCLEX lab values page.
Typical adult values used in nursing education. Each laboratory sets its own reference ranges, so use the range your facility or the question gives you.
Electrolytes
| Test | Typical adult range | Why it matters |
|---|---|---|
| Sodium (Na) | 135–145 mEq/L | Low or high sodium changes neurologic status. Watch for confusion and seizures, and correct slowly. |
| Potassium (K) | 3.5–5.0 mEq/L | Both low and high potassium cause dysrhythmias. Hyperkalemia: peaked T waves. Hypokalemia: U waves and higher risk of digoxin toxicity. |
| Chloride (Cl) | 98–106 mEq/L | Usually moves with sodium and affects acid-base balance. |
| Calcium, total (Ca) | 9.0–10.5 mg/dL | Low calcium: tetany and positive Chvostek and Trousseau signs. High calcium: muscle weakness and kidney stones. |
| Magnesium (Mg) | 1.3–2.1 mEq/L | High magnesium (for example during magnesium sulfate therapy) depresses deep tendon reflexes and respirations. |
| Phosphorus (P) | 3.0–4.5 mg/dL | Moves opposite to calcium. Often high in chronic kidney disease. |
Complete blood count
| Test | Typical adult range | Why it matters |
|---|---|---|
| Hemoglobin (Hgb) | Male 14–18 g/dL; female 12–16 g/dL | Low values mean anemia or bleeding. Check for tachycardia, pallor, and fatigue. |
| Hematocrit (Hct) | Male 42–52%; female 37–47% | Rises with dehydration and falls with bleeding or fluid overload. |
| White blood cells (WBC) | 5,000–10,000/mm³ | High suggests infection or inflammation. Low means infection risk: use neutropenic precautions. |
| Platelets | 150,000–400,000/mm³ | Below about 50,000/mm³, bleeding risk rises: avoid injections and use bleeding precautions. |
Coagulation
| Test | Typical adult range | Why it matters |
|---|---|---|
| Prothrombin time (PT) | 11–12.5 seconds | Monitors warfarin therapy along with the INR. |
| INR | 0.8–1.1 (no anticoagulant) | Warfarin target is usually 2–3, and higher for some mechanical heart valves. Vitamin K reverses warfarin. |
| aPTT | 30–40 seconds | Monitors IV unfractionated heparin; a common target is 1.5–2.5 times control. Protamine reverses heparin. |
Arterial blood gases
| Test | Typical adult range | Why it matters |
|---|---|---|
| pH | 7.35–7.45 | Below 7.35 is acidosis; above 7.45 is alkalosis. |
| PaCO₂ | 35–45 mm Hg | The respiratory part. High PaCO₂ with low pH is respiratory acidosis. |
| HCO₃⁻ (bicarbonate) | 22–26 mEq/L | The metabolic part. Low HCO₃⁻ with low pH is metabolic acidosis. |
| PaO₂ | 80–100 mm Hg | Below 80 mm Hg is hypoxemia. |
| SaO₂ | 95–100% | Interpret with the client's baseline; some clients with COPD have a lower target. |
Kidney function and glucose
| Test | Typical adult range | Why it matters |
|---|---|---|
| BUN | 10–20 mg/dL | Rises with dehydration, GI bleeding, and kidney injury. |
| Creatinine | 0.5–1.2 mg/dL | The better marker of kidney function. Check it before nephrotoxic drugs and contrast. |
| Fasting blood glucose | 70–99 mg/dL | Below 70 mg/dL is hypoglycemia: treat it right away. 126 mg/dL or higher on two tests suggests diabetes. |
| Hemoglobin A1C | Below 5.7% | 5.7–6.4% is prediabetes and 6.5% or higher is diabetes. Shows average glucose over about 3 months. |
Therapeutic drug levels
| Test | Typical adult range | Why it matters |
|---|---|---|
| Digoxin | 0.5–2.0 ng/mL | Many heart failure guidelines aim for the low end. Toxicity: nausea, vision changes, and bradycardia, made worse by low potassium. |
| Lithium | 0.6–1.2 mEq/L (maintenance) | Narrow range. Dehydration and low sodium raise levels; above about 1.5 mEq/L signs of toxicity appear. |
| Phenytoin | 10–20 mcg/mL | Toxicity causes nystagmus, ataxia, and confusion. |
Other high-yield values
| Test | Typical adult range | Why it matters |
|---|---|---|
| Albumin | 3.5–5.0 g/dL | Low albumin points to poor nutrition or liver disease, and to edema. |
| BNP | Below 100 pg/mL | Higher values support a diagnosis of heart failure. |
| Troponin | Below the lab's 99th percentile cutoff | A rise and fall above the cutoff means myocardial injury, such as a heart attack. Ranges depend on the assay. |
| Total cholesterol | Below 200 mg/dL | Part of cardiovascular risk assessment along with LDL and HDL. |
| Urine specific gravity | 1.005–1.030 | High suggests dehydration; low suggests overhydration or diabetes insipidus. |
How to study these
- Learn the direction first: what high and low each mean for the client and what you would do.
- Pair labs with drugs: potassium with digoxin and diuretics, INR with warfarin, aPTT with heparin, glucose with insulin.
- Know the critical ones cold: potassium, sodium, glucose, platelets, and the ABG values.
Sources
- Pagana KD, Pagana TJ, Pagana TN. Mosby's Manual of Diagnostic and Laboratory Tests.
- MedlinePlus Medical Tests (U.S. National Library of Medicine).
- American Diabetes Association. Standards of Care in Diabetes (A1C and glucose).
- FDA prescribing information (DailyMed) for digoxin, lithium, phenytoin, warfarin, and heparin.
For exam study only. In clinical practice, follow your facility's policies, the prescriber's orders, and current references. Free to print and share for personal and classroom study; not for resale. NCLEX® is a registered trademark of NCSBN, which does not endorse NCLEXSim.
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