A comprehensive metabolic panel, or CMP, is a set of 14 blood tests run from one tube. It checks your blood sugar, your electrolytes and fluid balance, how well your kidneys are filtering, and how well your liver is working. It is the single most common chemistry panel in US medicine, ordered at annual physicals, before surgery, and to monitor medicines that affect the liver or kidneys. Most labs ask you to fast, mainly for the glucose reading.

The 14 tests, in four groups

A CMP blood test looks long on paper, but the 14 values sort into four questions.

Blood sugar is one test: glucose. Drawn fasting, it screens for prediabetes and diabetes.

Electrolytes and minerals are five tests: sodium, potassium, chloride, bicarbonate (often listed as CO2), and calcium. Together they show hydration, acid-base balance, and the minerals your nerves and heart rhythm depend on.

Kidney function is two tests: blood urea nitrogen and creatinine, both waste products the kidneys clear. From creatinine, your age, and your sex, the lab calculates eGFR, the number used to stage kidney function.

Liver function and proteins are six tests: ALT and AST, enzymes that rise when liver cells are injured; alkaline phosphatase, which rises with bile duct and bone problems; bilirubin, the pigment the liver clears; and albumin and total protein, which the liver makes. Our guide to what tests are in a CMP goes through each line.

The metabolic panel is the workhorse of routine blood work for a reason: no other single tube covers sugar, kidneys, liver, and electrolytes at once.

Who should get a comprehensive metabolic panel

Most adults get one at an annual checkup, which is reasonable, because several of the conditions it catches are silent. Early kidney disease has no symptoms. Fatty liver, now the most common cause of abnormal liver enzymes in the US, usually has none either. A mildly high fasting glucose is the first sign of prediabetes, often years before anything is felt.

It is also the standard monitoring test for medications. Statins, many blood pressure drugs, diuretics, metformin, and most long-term prescriptions can affect the liver, kidneys, or potassium, so a comprehensive metabolic panel test before starting and periodically afterward is routine. The same applies to people with diabetes, kidney disease, high blood pressure, or liver disease, where the panel tracks the condition.

Symptoms that prompt one include unexplained fatigue, nausea, leg swelling, changes in urination, or abdominal discomfort. After an illness with vomiting or diarrhea, the electrolyte section shows whether you have recovered.

How to prepare

Fast for 8 to 12 hours if your order asks you to. MedlinePlus advises not eating or drinking for at least 8 hours before, and the reason is glucose: a meal raises it for hours and would make the fasting reading meaningless. The other 13 values barely move with food, so if you forgot and ate, the rest of the panel is still valid.

Water is encouraged. Dehydration concentrates the blood and nudges sodium, creatinine, and BUN upward, which is a common reason for a flagged kidney value in someone whose kidneys are fine.

Skip hard exercise the day before, since it raises ALT and AST. Take your usual medicines unless told otherwise, and ask about diabetes medicines if you will be fasting.

Reading your result

Every lab prints its own reference range, and that is the one to use. One flagged value on a 14-test panel is expected: ranges cover the middle 95 percent of healthy people, so by chance alone a long panel often flags something in someone who is well.

High glucose, if you fasted, means prediabetes or diabetes if it holds up on a repeat or an HbA1c. If you were not fasting, it means you ate.

High creatinine and BUN together usually mean dehydration or reduced kidney filtering. eGFR tells you which: a value of 90 or above is normal, 60 to 89 mildly reduced, and under 60 on two tests three months apart defines chronic kidney disease. High BUN with a normal creatinine is more often dehydration or a high-protein meal.

High ALT or AST means liver cells are irritated, most often from fatty liver, alcohol, medications, or a recent workout. Values many times the upper limit need prompt attention. High alkaline phosphatase and bilirubin together point to bile flow rather than liver cells.

Abnormal potassium or sodium matters more than most lines, because large deviations affect heart rhythm; small ones are often dehydration or a medication effect. Low albumin can reflect liver disease, kidney protein loss, inflammation, or poor nutrition.

Three related values moving together is a signal. One mild outlier usually is not.

What a comprehensive metabolic panel cannot tell you

It does not include cholesterol, thyroid function, blood counts, or vitamins. People sometimes call it a complete metabolic panel and assume it covers everything, but a lipid panel, a TSH, a CBC, and vitamin D are separate tests, which is why routine blood work usually bundles them with the CMP.

It also leaves out magnesium, despite magnesium being an electrolyte, and HbA1c, the three-month blood sugar average that a single fasting glucose cannot give. And it is a screen, not a diagnosis. A flagged liver enzyme says look closer; it does not say why.

CMP versus BMP

The basic metabolic panel is the first eight tests, without the six liver and protein tests. Hospitals use it to check electrolytes and kidneys quickly. For routine blood work, the comprehensive version is the usual choice because the price difference is small and the liver section is where fatty liver and medication effects show up. Our BMP vs CMP guide covers when each makes sense.

How to get tested

You can order one yourself. August's lab tests include a complete metabolic panel on its own and inside routine and metabolic panels, at one price that covers the draw. A phlebotomist comes to your home for a morning draw, which makes a metabolic panel drawn fasting simple, or you visit a nearby lab. Results post the next day in most cases, and a clinician reviews every one before you see it, so a flagged value comes with context. Critical values are escalated the same day. August Care members get up to 50 percent off next-day lab tests and a first consultation included.

Not sure whether a CMP is the right test for your symptoms? Describe them to August, a free AI health assistant, to help decide. It is a starting point, not a diagnosis.

Frequently Asked Questions

Fourteen things: fasting glucose, five electrolytes and minerals, two kidney markers, and six liver and protein markers. Together they screen blood sugar, hydration and acid-base balance, kidney filtering, and liver health. The lab also calculates eGFR from the creatinine value, which is the number used to stage kidney function.

Usually yes, for 8 to 12 hours, because glucose is on the panel and a meal raises it for hours. Water is fine and encouraged. If you eat by mistake, the glucose reading is unreliable but the other 13 values are still valid, so tell the lab rather than cancel.

No. A BMP is the first eight tests: glucose, calcium, four electrolytes, BUN, and creatinine. A CMP adds albumin, total protein, alkaline phosphatase, ALT, AST, and bilirubin, which assess the liver. For routine blood work the CMP is the usual choice, since the extra six are where fatty liver and medication effects appear.

It depends on which value and by how much. One mild flag on a 14-test panel is common and often reflects dehydration, a recent meal or workout, or a medication. Several related values out together, or a value far outside the range, warrant follow-up. A clinician reads the pattern rather than any single line.

No. Cholesterol is on a lipid panel and thyroid function is a TSH test, both separate. A CMP also leaves out blood counts, vitamins, HbA1c, and magnesium. Routine blood work usually pairs a CMP with a CBC and a lipid panel to cover those gaps.

Estimated glomerular filtration rate, a calculation of how well your kidneys filter, based on creatinine, age, and sex. Ninety or above is normal; 60 to 89 is mildly reduced and common with age; under 60 on two tests at least three months apart defines chronic kidney disease.

The most common reasons are fatty liver, alcohol, medications and supplements, or hard exercise in the previous day or two. A mild elevation is usually repeated after a few weeks of avoiding alcohol and heavy workouts. Persistent elevation leads to a closer look at the liver.

Yes. An August phlebotomist draws the sample at home, ideally in the morning after an overnight fast, and a certified lab runs the same analysis a clinic would. Results post the next day in most cases, each value shown against the lab's range, with a clinician's review.