Metabolic Panel (BMP and CMP): What Each Value Means

Basic Metabolic Panel (BMP):

• Sodium — fluid balance, neurologic function.
• Potassium — cardiac and muscle function; tightly regulated.
• Chloride — fluid and acid-base balance.
• Bicarbonate (CO₂) — acid-base balance.
• Blood urea nitrogen (BUN) — protein metabolism waste; kidney clearance.
• Creatinine — kidney filtration (with eGFR calculated).
• Glucose — fasting or random.
• Calcium — sometimes included in BMP, always in CMP.

Comprehensive Metabolic Panel (CMP) adds:

• Total protein, albumin — synthetic liver function and nutritional status.
• Bilirubin (total) — liver excretory function and hemolysis.
• Alkaline phosphatase (ALP) — liver/bile and bone.
• AST and ALT — liver injury markers.

The CMP costs about the same as a BMP at most labs and is the more useful panel in routine bloodwork.

Typical adult ranges (ranges vary slightly by lab and assay):

• Sodium: 136–145 mEq/L
• Potassium: 3.5–5.0 mEq/L
• Chloride: 98–107 mEq/L
• Bicarbonate (CO₂): 22–29 mEq/L
• BUN: 7–20 mg/dL
• Creatinine: 0.59–1.35 mg/dL (sex-dependent)
• eGFR: >60 mL/min/1.73m² is normal
• Glucose (fasting): 70–99 mg/dL
• Calcium: 8.6–10.3 mg/dL
• Total protein: 6.0–8.3 g/dL
• Albumin: 3.5–5.0 g/dL
• Bilirubin (total): 0.1–1.2 mg/dL
• ALP: 44–147 U/L
• AST: 8–48 U/L
• ALT: 7–55 U/L (lab); 7–33 men, 7–25 women (newer healthier-population cutoffs)

A handful of patterns drive most clinical decisions:

• BUN/Creatinine ratio above 20 + low bicarbonate → dehydration or prerenal kidney injury.
• BUN and creatinine both elevated, eGFR below 60 sustained → chronic kidney disease.
• High glucose on a fasting sample → impaired fasting glucose (100–125) or diabetes (≥126, confirmed).
• Low sodium (below 135) → typically dilutional (heart failure, kidney/liver disease, SIADH); rarely true sodium loss.
• High sodium (above 145) → almost always volume depletion or inadequate water intake.
• High potassium (above 5.0) → kidney disease, ACE inhibitors, ARBs, spironolactone, hemolyzed sample (most common cause of mildly elevated values), rhabdomyolysis.
• Low potassium (below 3.5) → diuretics, GI losses, refeeding.
• Low bicarbonate with elevated anion gap → metabolic acidosis (DKA, lactic acidosis, kidney failure, certain ingestions).
• High calcium (above 10.5) → hyperparathyroidism (most common in outpatients), malignancy, vitamin D excess, certain medications.
• Low albumin + abnormal liver enzymes → chronic liver disease.
• Low albumin + edema + protein in urine → nephrotic syndrome.
• High AST and ALT together → liver injury; AST > ALT favors alcohol or muscle, ALT > AST favors fatty liver or viral hepatitis.
• High ALP with normal AST/ALT → bile duct or bone pathology; check GGT to discriminate.
• High bilirubin with normal liver enzymes → Gilbert's syndrome (benign, common) or hemolysis.

• Hemolyzed samples falsely raise potassium, AST, and LDH. If only those values are abnormal and the lab notes hemolysis, repeat the draw.
• Dehydration distorts the entire panel — concentrating BUN, creatinine, sodium, hemoglobin, and others. Rehydration often resolves mild abnormalities.
• Recent food can elevate glucose and triglycerides; always fast for an accurate fasting glucose.
• Albumin correction for calcium: corrected calcium = measured calcium + 0.8 × (4.0 − albumin). Always correct calcium for albumin before interpreting.
• Mild isolated abnormalities are often noise; the same value off the same panel a month later usually returns to normal. Pursue patterns and trends, not single flags.

The metabolic panel is one of the highest-value tests to track over time. Patterns that warrant attention:

• Slow eGFR decline — even within the normal range, a drop of 5+ mL/min/year is the signature of progressive kidney disease.
• Drift toward higher fasting glucose — preceding diabetes by years, often with HbA1c rising in parallel.
• Persistent mild ALT elevation — most often metabolic-associated fatty liver disease (MASLD); track FIB-4 alongside.
• Falling albumin — chronic illness, malnutrition, or kidney protein loss.

• Potassium below 3.0 or above 6.0 — cardiac arrhythmia risk; immediate evaluation.
• Sodium below 125 or above 155 — neurologic risk; immediate evaluation.
• Glucose above 400 with symptoms — possible DKA or hyperosmolar state; emergency evaluation.
• Bicarbonate below 15 with elevated anion gap — significant metabolic acidosis; emergency evaluation.
• Acute creatinine doubling — acute kidney injury; investigate urgently.
• AST or ALT above 1000 — fulminant liver injury; emergency evaluation (consider acetaminophen toxicity, ischemic hepatitis).
• Calcium above 12 or below 7 — symptomatic in either direction; urgent evaluation.

• HbA1c — three-month glucose average; companion to fasting glucose.
• Lipid panel — usually ordered with the metabolic panel for cardiovascular risk.
• Urine albumin/creatinine ratio — kidney damage marker; pairs with creatinine and eGFR.
• Magnesium and phosphorus — additional electrolytes useful in advanced kidney disease and severe illness.
• GGT — discriminates liver vs. bone source of high alkaline phosphatase.
• Direct (conjugated) bilirubin — distinguishes obstructive from hemolytic hyperbilirubinemia.
• Thyroid panel — thyroid disease affects multiple metabolic values.