A CMP, or comprehensive metabolic panel, is a blood test that measures 14 different substances in your blood to give a broad snapshot of how well your body is functioning. It checks your blood sugar, kidney health, liver health, electrolyte balance, and protein levels all at once. Doctors order it routinely during annual checkups and also use it to monitor chronic conditions like diabetes or kidney disease.
What a CMP Measures
A single blood draw provides results for all 14 markers. These fall into a few natural groups based on what part of your body they reflect:
- Blood sugar: glucose
- Electrolytes: sodium, potassium, chloride, and bicarbonate (sometimes listed as CO2)
- Kidney markers: blood urea nitrogen (BUN) and creatinine
- Liver markers: alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate aminotransferase (AST), and bilirubin
- Proteins: albumin and total protein
- Mineral: calcium
No single number on this panel tells the full story. Your provider looks at patterns across the results, because one abnormal value can mean very different things depending on what the other values show.
Kidney Health: BUN and Creatinine
Your kidneys constantly filter waste from your blood. BUN and creatinine are two waste products that healthy kidneys clear efficiently. When kidney function declines, these levels rise because the waste is no longer being removed at the normal rate.
BUN can also increase from dehydration, a high-protein diet, or certain medications, so it’s not specific to kidney disease on its own. Creatinine is a more reliable indicator of how well your kidneys are filtering. When both are elevated together, it’s a stronger signal that kidney function needs a closer look. Your provider may calculate an estimated filtration rate from the creatinine result to get a clearer picture of overall kidney performance.
Liver Health: Enzymes and Bilirubin
Three liver enzymes appear on a CMP: ALP, ALT, and AST. These are proteins your liver produces in small amounts under normal conditions. When liver cells are damaged or inflamed, they release more of these enzymes into your bloodstream, causing levels to spike. Elevated ALT and AST together often point to liver inflammation, which can result from infections like hepatitis, fatty liver disease, alcohol use, or certain medications.
ALP is a bit different. It’s made in the liver but also in bone, so a high ALP level could signal either liver problems or bone conditions like Paget’s disease. Context from the other liver markers helps narrow down the cause.
Bilirubin is a yellowish waste product created when your body breaks down old red blood cells. Your liver processes and removes most of it. High bilirubin can indicate liver disease, bile duct blockages, or conditions that cause red blood cells to break down too quickly. Very high levels produce jaundice, the visible yellowing of skin and eyes.
Electrolytes and Fluid Balance
Sodium, potassium, chloride, and bicarbonate are electrically charged minerals that regulate how much water your body retains, how your nerves fire signals, and how your muscles contract. Even small imbalances can cause noticeable symptoms.
Low potassium, for example, can cause muscle weakness, cramps, or an irregular heartbeat. High sodium often reflects dehydration, while low sodium can result from drinking too much water or from certain hormonal disorders. Bicarbonate reflects your blood’s acid-base balance. If it’s off, your body may be compensating for a lung problem, kidney issue, or metabolic condition like uncontrolled diabetes. These four values together paint a picture of how well your body is managing its internal environment.
Blood Sugar
The glucose reading on a CMP tells you how much sugar is circulating in your blood at the time of the draw. If you’ve been asked to fast before the test, a normal fasting glucose generally falls between 70 and 100 mg/dL. Values between 100 and 125 suggest prediabetes, and 126 or above on two separate tests points toward diabetes.
Even without fasting, a very high glucose value is a red flag. A CMP isn’t the definitive test for diagnosing diabetes (that usually requires a fasting glucose or an A1C test), but it frequently provides the first clue that blood sugar management needs attention.
Proteins: Albumin and Total Protein
Your blood carries two main types of protein: albumin and globulins. The CMP measures albumin individually and also gives a total protein count that includes both types.
Albumin is made in the liver and has a surprisingly important job: it keeps fluid inside your blood vessels and acts as a transport vehicle for hormones, vitamins, and medications. Low albumin can signal liver disease, kidney disease, malnutrition, thyroid problems, or severe burns. Because it’s produced by the liver and lost through damaged kidneys, albumin sits at the crossroads of several organ systems.
Total protein levels that are too low may indicate malnutrition or conditions where the gut can’t absorb nutrients properly, like celiac disease or Crohn’s disease. Unusually high total protein can sometimes point toward chronic infections or, less commonly, blood cancers like multiple myeloma.
Calcium
About 99% of your body’s calcium lives in your bones and teeth. The 1% circulating in your blood is what the CMP measures, and that small fraction is critical. Blood calcium keeps your heart beating in rhythm, your muscles contracting, your nerves signaling, and your blood vessels functioning.
High blood calcium can be a sign of overactive parathyroid glands, bone disease, or certain cancers. Low calcium may point to kidney disease, vitamin D deficiency, or parathyroid problems. One thing the calcium number on a CMP cannot tell you is how strong your bones are. That requires a separate bone density scan.
CMP vs. Basic Metabolic Panel
You may see a basic metabolic panel (BMP) on your lab order instead of a CMP. A BMP includes 8 of the 14 markers: glucose, calcium, the four electrolytes, BUN, and creatinine. It covers blood sugar, kidney function, and electrolyte balance but leaves out the liver enzymes, bilirubin, albumin, and total protein.
A CMP adds those six extra markers to give a fuller picture that includes liver function and nutritional status. Providers typically order a CMP when they want a broader baseline or when they’re monitoring conditions that affect the liver. A BMP is often sufficient for simpler follow-ups, like checking kidney function in someone taking blood pressure medication.
Preparation and What to Expect
Your provider will likely ask you to fast for 10 to 12 hours before the blood draw, primarily because eating affects your glucose reading. Water is usually fine during the fasting period. Some medications can also influence results, so let your provider know what you’re taking.
The test itself is a standard blood draw from a vein in your arm. It takes a few minutes, and results are typically available within one to two business days. There’s very little risk beyond minor bruising or soreness at the puncture site.
Reading Your Results
Lab reports list each of the 14 values alongside a reference range, which represents what’s considered normal for most healthy adults. If a number falls outside that range, it’s flagged as high or low. A single out-of-range value doesn’t necessarily mean something is wrong. Mild deviations can result from what you ate, how hydrated you were, medications, or even intense exercise the day before.
What matters most is the pattern. A cluster of abnormal liver markers tells a different story than one slightly elevated enzyme. Consistently abnormal kidney values over multiple tests carry more weight than a single borderline result. Your provider interprets the panel as a whole and compares it against previous results to spot trends rather than reacting to any one number in isolation.