Labs and Abnormal Value Interpretation
Review the high-yield NCLEX lab values from the session compiler with low/high findings and priority nursing actions.
Lab interpretation table
Study ranges are broad references. Use school and facility ranges for exams and clinical work.
| Lab | Normal range | Meaning | Low / high clues | Priority actions |
|---|---|---|---|---|
| Sodium | 135-145 mEq/L | Water balance and neurologic status. Sodium swells or shrinks the brain. | Low: Confusion, Headache, Seizures High: Thirst, Dry mucosa, Restlessness | Institute seizure precautions for severe symptoms. Trend correction rate as ordered. |
| Potassium | 3.5-5.0 mEq/L | Cardiac conduction and muscle function. K kills. | Low: Weakness, U waves, Constipation High: Peaked T waves, Weakness, Cardiac arrest risk | Place symptomatic or critical abnormal values on cardiac monitor. Never IV push potassium. |
| Calcium | 8.5-10.5 mg/dL | Bone, clotting, neuromuscular excitability, and cardiac conduction. Low calcium is twitchy; high calcium is slow and stony. | Low: Tetany, Tingling, Seizures High: Kidney stones, Constipation, Confusion | Watch airway spasm/seizures when low. Promote hydration and safety when high if allowed. |
| Magnesium | 1.7-2.2 mg/dL | Neuromuscular calming and cardiac rhythm stability. Magnesium calms; too much shuts down. | Low: Tremors, Seizures, Torsades risk High: Absent reflexes, Respiratory depression, Hypotension | Monitor reflexes and respirations during magnesium infusion. Keep calcium gluconate available when ordered. |
| BUN / Creatinine | BUN 10-20 mg/dL; creatinine about 0.6-1.3 mg/dL | Kidney perfusion and filtration trends. Creatinine is kidney filter trend. | High: Dehydration, AKI/CKD, Medication dosing risk | Trend urine output and nephrotoxic medication risk. Escalate rising creatinine with low urine output. |
| WBC | 4,500-11,000/mm3 | Infection, inflammation, marrow response, or immunosuppression. | Low: Neutropenia infection risk High: Infection/inflammation, Stress response | Use neutropenic precautions when indicated. Trend with fever and cultures. |
| Hgb / Hct | Hgb about 12-18 g/dL; Hct about 36-54% | Oxygen-carrying capacity and bleeding/anemia trend. | Low: Fatigue, Dyspnea, Bleeding/anemia High: Dehydration or polycythemia concern | Assess active bleeding and oxygenation. Trend after GI bleed, trauma, or surgery. |
| Platelets | 150,000-400,000/mm3 | Primary clot formation. | Low: Bruising, Petechiae, Bleeding High: Clot risk in selected contexts | Bleeding precautions when low. Avoid IM injections if severely low per policy. |
| PT / INR | PT about 11-13.5 sec; INR about 0.8-1.1 unless anticoagulated | Extrinsic clotting pathway; warfarin monitoring context. Warfarin watches PT/INR. | High: Bleeding risk, Liver dysfunction, Warfarin effect | Assess bleeding and medication safety. Know vitamin K reversal context for warfarin. |
| aPTT | About 25-35 sec unless anticoagulated | Intrinsic clotting pathway; heparin monitoring context. Heparin has two Ps in aPTT. | High: Bleeding risk, Heparin effect | Assess bleeding with heparin therapy. Know protamine reversal context for heparin. |
| Glucose | Fasting about 70-99 mg/dL | Immediate brain fuel and diabetes control. | Low: Sweaty, Shaky, Confused, Seizure High: Polyuria, Thirst, DKA/HHS risk | Treat symptomatic hypoglycemia promptly. Check ketones/acid-base when DKA suspected. |
| Albumin | 3.5-5.0 g/dL | Protein/nutrition status and oncotic pressure. | Low: Edema, Poor wound healing, Ascites risk | Assess nutrition, liver disease, kidney loss, and wound risk. |
| Ammonia | Varies by lab; commonly about 15-45 mcg/dL | Liver detoxification and encephalopathy trend. Ammonia clouds the brain. | High: Confusion, Asterixis, Lethargy | Assess airway/safety and lactulose response when ordered. |
| Troponin | Lab-specific; normally very low/undetectable | Myocardial injury marker. | High: MI/ACS concern, Other myocardial strain/injury contexts | Pair with symptoms and ECG. Escalate chest pain plus elevated/rising value. |
| BNP | Lab-specific; often <100 pg/mL used as a low-risk reference | Heart stretch and heart failure support marker. | High: Heart failure exacerbation context, Volume/pressure overload | Assess dyspnea, edema, weight, and lung sounds with the value. |
| ABG pH | 7.35-7.45 | Overall acid-base direction. | Low: Acidosis High: Alkalosis | Use pH first to decide acid versus alkalotic state. |
| PaCO2 | 35-45 mm Hg | Respiratory acid controlled by ventilation. CO2 equals respiratory. | Low: Respiratory alkalosis direction High: Respiratory acidosis direction | Assess ventilation, airway, and breathing when PaCO2 drives the problem. |
| HCO3 | 22-26 mEq/L | Metabolic base controlled mainly by kidneys. HCO3 equals metabolic. | Low: Metabolic acidosis direction High: Metabolic alkalosis direction | Look for DKA, renal failure, GI losses, or vomiting based on direction. |