Critical values highlighted. 35+ labs across 6 categories.
| Test | Normal Range | Critical Low | Critical High | Key Nursing Point |
|---|---|---|---|---|
| WBC | 4,500–11,000/mm³ | <2,000 | >30,000 | Low = infection risk (neutropenic precautions); High = infection or leukemia |
| RBC (Male) | 4.5–5.5 million/mm³ | <3.0 | >6.5 | Low = anemia; High = polycythemia |
| RBC (Female) | 4.0–5.0 million/mm³ | <3.0 | >6.5 | Low = anemia; High = polycythemia |
| Hemoglobin (Male) | 14–18 g/dL | <7 | >20 | Low = fatigue, tachycardia; transfuse if <7 or symptomatic |
| Hemoglobin (Female) | 12–16 g/dL | <7 | >20 | Low = fatigue, tachycardia; transfuse if <7 or symptomatic |
| Hematocrit (Male) | 40–54% | <25% | >60% | Low = bleeding/anemia; High = dehydration or polycythemia |
| Hematocrit (Female) | 36–48% | <25% | >60% | Low = bleeding/anemia; High = dehydration or polycythemia |
| Platelets | 150,000–400,000/mm³ | <50,000 | >1,000,000 | Low = bleeding precautions; <20,000 = spontaneous bleeding risk |
| Test | Normal Range | Critical Low | Critical High | Key Nursing Point |
|---|---|---|---|---|
| Sodium (Na+) | 136–145 mEq/L | <120 | >160 | Low = confusion, seizures; High = thirst, dry mucous membranes |
| Potassium (K+) | 3.5–5.0 mEq/L | <3.0 | >6.0 | CRITICAL: Cardiac dysrhythmias at both extremes. Check ECG. |
| Chloride (Cl-) | 98–106 mEq/L | <80 | >115 | Follows sodium; Low in vomiting (metabolic alkalosis) |
| CO2/Bicarb (HCO3) | 22–26 mEq/L | <15 | >40 | Low = metabolic acidosis; High = metabolic alkalosis |
| BUN | 10–20 mg/dL | <5 | >100 | High = dehydration or renal failure; check with creatinine |
| Creatinine | 0.6–1.2 mg/dL | — | >4.0 | Best indicator of renal function. Rising = kidney injury |
| Glucose (Fasting) | 70–100 mg/dL | <40 | >400 | Low = give 15g carbs (15-15 rule); High = assess for DKA/HHS |
| Calcium (Ca²+) | 8.5–10.5 mg/dL | <6.0 | >13.0 | Low = Trousseau/Chvostek signs, tetany; High = cardiac arrest risk |
| Magnesium (Mg²+) | 1.5–2.5 mEq/L | <1.0 | >4.0 | Low = tremors, seizures; High = hyporeflexia, respiratory depression |
| Phosphorus | 2.5–4.5 mg/dL | <1.0 | >7.0 | Inverse relationship with calcium. Low = muscle weakness |
| Test | Normal Range | Critical Low | Critical High | Key Nursing Point |
|---|---|---|---|---|
| PT | 11–13.5 seconds | — | >20 | Monitors warfarin therapy. Elevated = bleeding risk |
| INR | 0.8–1.1 (2.0–3.0 on warfarin) | — | >4.5 | Warfarin target: 2.0–3.0 (mechanical valve: 2.5–3.5) |
| aPTT | 25–35 seconds | — | >70 | Monitors heparin therapy. Target: 1.5–2.5× control |
| D-Dimer | <500 ng/mL | — | >500 | Elevated = clot breakdown (DVT, PE, DIC). Sensitive not specific |
| Fibrinogen | 200–400 mg/dL | <100 | — | Low in DIC. Critically low = massive hemorrhage risk |
| Test | Normal Range | Critical Low | Critical High | Key Nursing Point |
|---|---|---|---|---|
| Troponin I | <0.04 ng/mL | — | >0.4 | GOLD STANDARD for MI. Rises 3-6h, peaks 12-24h |
| BNP | <100 pg/mL | — | >900 | Heart failure marker. Higher = worse HF severity |
| CK-MB | <5 ng/mL | — | >10 | Cardiac-specific CK isoenzyme. Rises 4-8h after MI |
| CK (Total) | 30–170 U/L | — | >10,000 | Very high = rhabdomyolysis. Hydrate aggressively |
| Test | Normal Range | Critical Low | Critical High | Key Nursing Point |
|---|---|---|---|---|
| AST (SGOT) | 10–40 U/L | — | >1,000 | Liver AND heart/muscle. Very high = acute hepatitis |
| ALT (SGPT) | 7–56 U/L | — | >1,000 | Most specific liver enzyme |
| Albumin | 3.5–5.0 g/dL | <2.0 | — | Low = malnutrition, liver disease. Edema risk |
| Bilirubin (Total) | 0.1–1.2 mg/dL | — | >12 | Elevated = jaundice |
| Ammonia | 15–45 mcg/dL | — | >100 | High = hepatic encephalopathy. Give lactulose |
| Test | Normal Range | Critical Low | Critical High | Key Nursing Point |
|---|---|---|---|---|
| TSH | 0.5–4.0 mIU/L | <0.01 | >10 | HIGH TSH = hypothyroid; LOW TSH = hyperthyroid |
| Free T4 | 0.8–1.8 ng/dL | <0.4 | >4.0 | Low = hypothyroid; High = hyperthyroid |
| Free T3 | 2.3–4.2 pg/mL | <1.0 | >8.0 | Most active thyroid hormone |
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