What Is a Comprehensive Metabolic Panel (CMP)?

A Comprehensive Metabolic Panel — commonly called a CMP — is one of the most ordered blood tests in medicine. It gives your doctor (or you) a snapshot of how your body's major organ systems are functioning, all from a single blood draw.

If you have had a routine physical, there is a good chance a CMP was part of it. But what exactly does it measure, and what do the results mean?

A CMP measures 14 different markers grouped into four categories:

• Glucose — your blood sugar level at the time of the draw. Elevated fasting glucose can indicate prediabetes or diabetes.

• BUN (Blood Urea Nitrogen) — a waste product filtered by the kidneys. High levels suggest the kidneys are not filtering efficiently.
• Creatinine — another waste product. Elevated creatinine is a reliable indicator of reduced kidney function.
• BUN/Creatinine Ratio — the relationship between these two markers helps distinguish kidney disease from dehydration or other causes.
• eGFR (Estimated Glomerular Filtration Rate) — calculated from creatinine, age, and sex. It estimates how well your kidneys are filtering blood per minute.

• ALT (Alanine Aminotransferase) — an enzyme that leaks into the blood when liver cells are damaged. Elevated ALT is one of the earliest signs of liver stress.
• AST (Aspartate Aminotransferase) — another liver enzyme. Elevated AST alongside ALT strongly suggests liver damage.
• ALP (Alkaline Phosphatase) — elevated levels can indicate liver disease, bile duct obstruction, or bone disorders.
• Total Bilirubin — a byproduct of red blood cell breakdown processed by the liver. High bilirubin causes jaundice and can indicate liver or bile duct problems.
• Total Protein — measures albumin and globulin together. Low levels can indicate liver disease, kidney disease, or malnutrition.
• Albumin — the most abundant protein in blood, made by the liver. Low albumin suggests chronic liver disease or poor nutrition.

• Sodium — regulates fluid balance and nerve function. Abnormal levels can indicate dehydration, kidney problems, or hormonal issues.
• Potassium — critical for heart and muscle function. Both high and low potassium can cause dangerous heart rhythm problems.
• Carbon Dioxide (CO2/Bicarbonate) — reflects the body's acid-base balance. Abnormal levels can indicate kidney or lung problems.
• Calcium — important for bone health, nerve function, and muscle contraction. Abnormal calcium can indicate parathyroid disorders, vitamin D deficiency, or cancer.
• Chloride — works with sodium to maintain fluid balance. Usually interpreted alongside sodium and CO2.

A Basic Metabolic Panel (BMP) includes 8 of the same markers — glucose, BUN, creatinine, sodium, potassium, CO2, chloride, and calcium — but skips the liver function tests (ALT, AST, ALP, bilirubin, total protein, albumin).

If your doctor is primarily monitoring kidney function, blood sugar, or electrolytes, a BMP may be sufficient. If they want a broader picture that includes liver health, a CMP is the better choice.

For most annual wellness screenings, a CMP provides more useful information for a modest price difference.

Yes — for the most accurate glucose reading, you should fast for 8–12 hours before a CMP. Water is fine. Black coffee and medications are generally acceptable, but check with your ordering provider if you are unsure.

If you eat before the draw, your glucose result will reflect your post-meal blood sugar rather than your fasting baseline, which makes it harder to screen for diabetes or prediabetes.

A CMP can flag early signs of:

• Type 2 diabetes or prediabetes (elevated fasting glucose)
• Chronic kidney disease (elevated creatinine, low eGFR)
• Liver disease or damage (elevated ALT, AST, ALP, or bilirubin)
• Dehydration (elevated BUN, abnormal sodium)
• Electrolyte imbalances (abnormal sodium, potassium, calcium)
• Malnutrition (low albumin or total protein)
• Medication side effects — many common medications (statins, NSAIDs, blood pressure drugs) can affect kidney or liver markers

A CMP is appropriate for almost anyone doing routine health monitoring. It is especially valuable if you:

• Are over 40 and have not had bloodwork in the past year
• Take prescription medications that can affect the liver or kidneys
• Have a family history of diabetes, kidney disease, or liver disease
• Drink alcohol regularly
• Have been experiencing fatigue, swelling, or unexplained weight changes
• Are managing high blood pressure or high cholesterol

Each lab provides reference ranges alongside your results. A result outside the reference range does not automatically mean something is wrong — ranges are based on population averages, and a single abnormal value often needs context.

What matters more is the pattern:

• A mildly elevated ALT in isolation may be nothing. ALT elevated alongside AST and ALP is more significant.
• A slightly low eGFR in a well-hydrated young person is different from the same result in a 65-year-old with high blood pressure.

If any of your results fall outside the reference range, follow up with a physician who can interpret them in the context of your full health history.

You do not need a physician's order to get a CMP in most states. At Reliable Exams, you can order a CMP online and have your blood drawn at any of 4,500+ LabCorp or Quest Diagnostics locations nationwide — no appointment needed.

Results are typically available within 1–2 business days and sent directly to you.

Order a Comprehensive Metabolic Panel — or explore our wellness panels that include a CMP alongside other key markers for a more complete picture of your health.