What Is a Comprehensive Metabolic Panel (CMP)?

A Comprehensive Metabolic Panel (CMP) is a blood test that measures 14 substances in your blood to assess your body's chemical balance, metabolism, kidney function, and liver health. It is one of the most commonly ordered lab tests during annual physicals, pre-surgical evaluations, and when monitoring chronic conditions.

What the CMP Measures

Kidney Function

• BUN (Blood Urea Nitrogen) — waste product from protein breakdown; elevated with kidney dysfunction or dehydration.
• Creatinine — waste product from muscle activity; the key marker of kidney filtration rate.
• BUN/Creatinine Ratio — helps distinguish dehydration from intrinsic kidney disease.

Liver Function

• ALT (Alanine Aminotransferase) — enzyme released when liver cells are damaged; specific to the liver.
• AST (Aspartate Aminotransferase) — enzyme found in liver, heart, and muscles; elevated in liver damage and muscle injury.
• ALP (Alkaline Phosphatase) — enzyme related to bile ducts and bone; elevated in biliary obstruction, liver disease, and bone disorders.
• Bilirubin — yellow pigment from broken-down red blood cells; high levels cause jaundice and signal liver or bile duct problems.

Electrolytes

• Sodium — key electrolyte for fluid balance, nerve function, and muscle contraction.
• Potassium — critical for heart rhythm and muscle function.
• Chloride — maintains acid-base balance.
• CO2 (Bicarbonate) — reflects the body's acid-base status.

Proteins & Other

• Albumin — main blood protein made by the liver; low levels indicate liver disease, malnutrition, or kidney protein loss.
• Total Protein — albumin and globulins combined.
• Glucose — blood sugar; screens for diabetes.
• Calcium — mineral regulated by parathyroid hormone; involved in bone health, nerve signaling, and clotting.

CMP vs BMP

A Basic Metabolic Panel (BMP) contains 8 of the 14 tests — it excludes the liver-related measures (ALT, AST, ALP, bilirubin, albumin, and total protein). Your provider chooses a BMP when only kidney function and basic chemistry are needed, and a CMP when liver function also needs to be assessed.

Fasting Requirements

A CMP is typically done after an 8–12 hour fast (water only) because food intake can affect glucose, certain electrolytes, and liver markers. Your provider or testing site will confirm whether fasting is required for your specific test.