A comprehensive metabolic panel, or CMP, is a blood test that measures 14 different substances in your blood to give a broad picture of how well your kidneys, liver, and metabolism are functioning. It’s one of the most commonly ordered lab tests in medicine, often included in routine checkups and used to monitor chronic conditions like diabetes or liver disease. A single blood draw provides results for all 14 markers at once.
What the 14 Markers Tell You
The CMP covers four general categories: blood sugar, electrolytes, kidney function, and liver function. Each marker reflects something different about your body’s chemistry.
- Glucose: Your blood sugar level, used to screen for or monitor diabetes.
- Calcium: Important for bones, nerves, and muscle function. Abnormal levels can point to issues with the parathyroid glands, kidneys, or bones.
- Sodium, potassium, chloride, and bicarbonate: These four electrolytes control fluid balance, nerve signaling, and the acid-base balance of your blood.
- BUN (blood urea nitrogen) and creatinine: Two waste products your kidneys filter out. When levels rise, it suggests your kidneys may not be working efficiently.
- Albumin and total protein: Proteins made largely by the liver. Low levels can signal liver disease, kidney disease, or nutritional deficiencies.
- ALT, AST, and ALP: Three enzymes that rise when liver cells are damaged or bile flow is blocked. ALP can also increase with certain bone conditions.
- Bilirubin: A yellow substance produced when red blood cells break down. Your liver processes it for removal. High bilirubin can cause jaundice and often points to liver or bile duct problems.
Kidney Markers: BUN and Creatinine
Both BUN and creatinine are waste products your body produces naturally. BUN forms when your body breaks down protein from food, while creatinine comes from normal muscle activity. Healthy kidneys filter both out through urine, so elevated levels in the blood are a red flag that your kidneys may be struggling.
A small amount of each substance in the blood is completely normal. Your results become concerning only when levels are consistently higher than the reference range. Temporary spikes can happen from dehydration or eating a very high-protein meal, which is one reason your provider may ask you to fast or repeat the test before drawing conclusions. If kidney disease is suspected, your provider will typically order additional testing beyond what the CMP alone can reveal.
Liver Markers: Enzymes, Protein, and Bilirubin
The CMP includes five markers related to liver health. Three of them, ALT, AST, and ALP, are enzymes normally contained inside liver cells. When those cells are damaged by infection, medication, alcohol, or fatty liver disease, the enzymes leak into the bloodstream and show up as elevated numbers on your results.
ALT is the most liver-specific of the three. AST also exists in muscle tissue, so a high AST with a normal ALT could reflect muscle injury rather than a liver problem. ALP is found in both liver and bone, so elevated ALP alone doesn’t necessarily mean liver damage.
Albumin and total protein round out the liver picture. Albumin is the most abundant protein in your blood, and your liver manufactures it. Persistently low albumin can indicate chronic liver disease, kidney disease that causes protein loss in urine, or poor nutrition. The ratio between albumin and other blood proteins (called globulins) can also offer clues. A low ratio has been associated with autoimmune conditions, liver cirrhosis, and kidney disease, while a high ratio is less common and may warrant further evaluation.
Bilirubin is the byproduct of old red blood cells being recycled. The liver processes bilirubin so it can leave the body in stool. When the liver is inflamed or a bile duct is blocked, bilirubin backs up into the blood. Mildly elevated bilirubin is relatively common and not always a concern, but significantly high levels can turn the skin and eyes yellow.
Electrolytes and Blood Sugar
Sodium, potassium, chloride, and bicarbonate work together to regulate how much water your cells hold, how your nerves fire, and whether your blood is too acidic or too alkaline. Even small shifts in potassium, for instance, can affect heart rhythm. Bicarbonate (sometimes listed as CO2 on your results) reflects your body’s acid-base status and can flag respiratory or metabolic problems.
Glucose is a straightforward measure of blood sugar at the time of the draw. A fasting glucose above 126 mg/dL on two separate tests is one of the standard criteria for diagnosing diabetes, while values between 100 and 125 mg/dL fall into the prediabetes range. Because eating raises blood sugar, you’re typically asked to fast before the test so the reading reflects your baseline.
CMP vs. Basic Metabolic Panel
You may also see a “BMP,” or basic metabolic panel, on lab orders. A BMP measures eight of the same substances: glucose, calcium, the four electrolytes, BUN, and creatinine. A CMP includes all eight of those plus the six liver and protein markers (ALT, AST, ALP, bilirubin, albumin, and total protein). If your provider only needs to check kidney function and electrolytes, a BMP is sufficient. If they also want a look at your liver, they’ll order the full CMP.
How To Prepare
Most providers ask you to fast for 10 to 12 hours before a CMP. Water is fine, but food and beverages other than water can affect your glucose reading and, to a lesser extent, some of the other markers. The test itself is a standard blood draw from a vein in your arm, and results are typically available within one to two business days.
If you’re ordering a CMP on your own through a direct-to-consumer lab, expect to pay in the range of $50 to $55 without insurance. With insurance, a CMP ordered by your provider is usually covered as part of routine care with little to no copay.
Reading Your Results
Your lab report will show each of the 14 values alongside a reference range. These ranges can vary slightly between labs, so always compare your number to the range printed on your specific report rather than a number you found online. A result flagged as “high” or “low” doesn’t automatically mean something is wrong. A single out-of-range value could reflect dehydration, a recent meal, intense exercise, or a medication side effect.
Patterns matter more than isolated numbers. A provider looking at your CMP is reading it like a story: elevated BUN and creatinine together suggest a kidney issue, while elevated ALT and AST together point toward the liver. A single mildly abnormal result in an otherwise normal panel is often rechecked before any further workup. If multiple markers in the same category are off, or if a value is far outside the normal range, that typically prompts additional targeted testing to pinpoint the cause.