Reference — Lab
BMP & CMP Reference for Nurses
Basic Metabolic Panel and Comprehensive Metabolic Panel — electrolytes, renal markers, glucose, albumin, and liver enzymes with normal ranges, clinical significance, and interpretation pearls.
Educational use only. Reference ranges vary by institution. Always interpret labs in clinical context. BMP includes the first 7 components; CMP adds the 6 liver/protein markers. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Basic Metabolic Panel (BMP)
Sodium, Potassium, Chloride, Bicarbonate (electrolytes) + BUN, Creatinine (renal) + Glucose
| Test | Normal | Low (↓) | High (↑) | Clinical Note |
|---|---|---|---|---|
| Sodium (Na⁺) | 135–145 mEq/L | Hyponatremia — SIADH, diuretics, HF, cirrhosis, water excess | Hypernatremia — free water deficit, DI, inadequate intake | Primary water balance indicator; correct ≤ 10–12 mEq/L per 24h |
| Potassium (K⁺) | 3.5–5.0 mEq/L | Hypokalemia — diuretics, vomiting, NG suction, alkalosis | Hyperkalemia — AKI/CKD, ACE inhibitors, acidosis, hemolysis | Never IV push K⁺; monitor ECG; correct Mg first if K remains low |
| Chloride (Cl⁻) | 98–106 mEq/L | Hypochloremia — vomiting, NG suction, diuretics, metabolic alkalosis | Hyperchloremia — dehydration, metabolic acidosis, NS excess | Follows Na; low Cl often accompanies hyponatremia and metabolic alkalosis |
| Bicarbonate (HCO₃⁻ / CO₂) | 22–29 mEq/L | Metabolic acidosis — DKA, lactic acidosis, diarrhea, renal failure | Metabolic alkalosis — vomiting, diuretics, corticosteroids, antacid excess | Serum CO₂ on metabolic panel reflects bicarbonate — not the same as PaCO₂ on ABG |
| BUN (Blood Urea Nitrogen) | 7–20 mg/dL | Liver failure (impaired urea production), malnutrition | Pre-renal azotemia (dehydration, reduced perfusion), AKI, CKD, high protein intake, GI bleeding | BUN:Cr ratio > 20:1 = pre-renal; < 10:1 = intrinsic renal or liver disease |
| Creatinine | 0.6–1.2 mg/dL (M); 0.5–1.1 mg/dL (F) | Low muscle mass (elderly, malnourished) — not clinically significant | AKI, CKD — rises when ~50% of nephrons are lost; less sensitive to early kidney dysfunction | More reliable than BUN alone for renal function; trend is more important than any single value |
| Glucose | 70–99 mg/dL (fasting); < 180 mg/dL (non-fasting) | Hypoglycemia — insulin excess, sulfonylureas, adrenal insufficiency, fasting | Hyperglycemia — DM, stress response, steroids, TPN, infection | Critical low: < 50 mg/dL — treat immediately. Random glucose > 200 mg/dL = diagnostic for DM |
CMP-Only Additions (Liver Panel + Proteins)
Comprehensive Metabolic Panel = BMP + ALT, AST, ALP, Total Bilirubin, Albumin, Total Protein
| Test | Normal | Clinical Significance | Key Note |
|---|---|---|---|
| ALT (Alanine Aminotransferase) | 7–56 units/L | Most specific liver enzyme — rises in hepatocellular damage, viral hepatitis, NAFLD, drug-induced liver injury | ALT > AST ratio suggests hepatocellular cause; AST > ALT ratio suggests alcoholic hepatitis |
| AST (Aspartate Aminotransferase) | 10–40 units/L | Rises in liver damage, but also with muscle injury (MI, rhabdomyolysis, myositis) | Less liver-specific than ALT — elevated AST with normal ALT may indicate muscle injury |
| ALP (Alkaline Phosphatase) | 44–147 units/L | Elevated in cholestatic liver disease (bile duct obstruction, primary biliary cholangitis), bone disease, pregnancy | Isolated ALP elevation with normal ALT/AST points to cholestasis or bone — check GGT to differentiate |
| Total Bilirubin | 0.2–1.2 mg/dL | Elevated in liver disease, hemolysis (indirect), bile duct obstruction (direct). Jaundice visible at > 2–3 mg/dL | Direct (conjugated) vs indirect (unconjugated) ratio helps identify cause: indirect = hemolysis; direct = obstruction or hepatitis |
| Albumin | 3.5–5.0 g/dL | Marker of nutritional status and hepatic synthetic function. Low in malnutrition, liver disease, nephrotic syndrome, inflammation | Corrects serum calcium: corrected Ca = measured Ca + (0.8 × [4 − albumin]). Low albumin = falsely low Ca |
| Total Protein | 6.0–8.3 g/dL | Sum of albumin + globulin. Decreased in malnutrition, liver failure, nephrotic syndrome; increased in dehydration, multiple myeloma | Use albumin-to-globulin ratio for further differentiation — elevated globulin fraction suggests inflammatory or autoimmune process |
BUN:Creatinine Ratio
| Ratio | Interpretation | Common Causes | Nursing Priority |
|---|---|---|---|
| > 20:1 | Pre-renal azotemia | Dehydration, hypovolemia, heart failure, reduced renal perfusion, GI bleeding (blood digested = urea load) | Fluid resuscitation; assess volume status; identify bleeding source |
| 10–20:1 | Normal | Normal renal function with adequate perfusion | Continue monitoring |
| < 10:1 | Intrinsic renal disease or liver failure | Glomerulonephritis, ATN, rhabdomyolysis, liver disease (impaired urea synthesis), malnutrition, SIADH | Assess for kidney damage, hold nephrotoxins; consult nephrology |
NCLEX Focus Points
Anion gap: Na − (Cl + HCO₃) = normal 8–12 mEq/L. High anion gap metabolic acidosis = MUDPILES (Methanol, Uremia, DKA, Propylene glycol, Isoniazid, Lactic acidosis, Ethylene glycol, Salicylates).
Serum CO₂ vs PaCO₂: The CO₂ on a metabolic panel is bicarbonate (HCO₃⁻), not the PCO₂ on an ABG. Students commonly confuse these.
Albumin correction for calcium: Critical NCLEX application — always adjust serum Ca when albumin is low.
Creatinine and eGFR: Serum creatinine alone is a late indicator — eGFR (estimated GFR) is more sensitive for detecting early CKD. Normal eGFR ≥ 60 mL/min/1.73m².
Liver enzymes pattern: Hepatocellular injury → elevated ALT/AST (ALT > AST for most causes; AST > ALT for alcoholic hepatitis). Cholestatic → elevated ALP and bilirubin with relatively normal ALT/AST.
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with Standard laboratory reference ranges · Clinical & Laboratory Standards Institute (CLSI). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →