Comprehensive Metabolic Panel (CMP)

What is a comprehensive metabolic panel (CMP) blood test?

A comprehensive metabolic panel (CMP) is a blood test that measures 14 different substances — like proteins and electrolytes — in your blood. It’s a routine test that can give your healthcare provider a picture of your overall physical health. It can help diagnose, screen for or monitor certain health conditions.

CMP tests can measure or monitor:

• How well your liver and kidneys are working.
• Your blood sugar levels.
• Your fluid and electrolyte balance.
• Your body’s response to treatments.

What tests are in a comprehensive metabolic panel?

The 14 substances measured in a CMP include:

• Alanine transaminase (ALT).
• Albumin.
• Alkaline phosphatase (ALP).
• Aspartate aminotransferase (AST).
• Bilirubin.
• BUN (blood urea nitrogen).
• Calcium.
• Carbon dioxide (bicarbonate).
• Chloride.
• Creatinine.
• Glucose.
• Potassium.
• Sodium.

These include enzymes and waste products that indicate how well your liver and kidneys are working, and minerals, sugars and other substances that your body needs to be in balance to stay healthy.

CMP liver function tests

These CMP tests check how well your liver is working:

• Bilirubin. This is a waste product that’s made from the breakdown of red blood cells.
• Albumin. This is a protein that your liver makes. It transports important substances through your bloodstream and keeps fluid from leaking out of your blood vessels.
• Liver enzymes. ALP, ALT and AST are liver enzymes, proteins that help certain processes in your body happen.
• Total protein. This is a measurement of the total amount of albumin and globulins, proteins in your blood.

CMP kidney function tests

These CMP tests check how well your kidneys are working:

• BUN (blood urea nitrogen). This is a measurement of urea nitrogen, which is a waste product that your kidneys help remove from your blood.
• Creatinine. This is a byproduct of muscle activity. It’s a waste product that your kidneys filter and remove from your blood.

CMP electrolyte tests

Electrolytes in your blood control nerve and muscle function. They also maintain the acid-base balance (pH balance) of your blood, maintain the fluid balance in your body and more. Electrolytes measured as part of a CMP include:

• Sodium. Most of your sodium comes from the food you eat. Your kidneys help regulate your body’s sodium levels.
• Potassium. Potassium comes from the food you eat and is present in all tissues of your body.
• Bicarbonate. Bicarbonate indicates the amount of carbon dioxide (CO₂) in your blood. CO₂ is a waste product that’s transported from your tissues, through your blood to your lungs, where you breathe it out of your body.
• Chloride. Chloride functions along with sodium, potassium and bicarbonate to control many processes in your body.

Other CMP tests

A CMP also measures your levels of glucose and calcium:

• Glucose. This is a type of sugar that provides energy for your body and brain. Glucose is also known as blood sugar.
• Calcium. Calcium is one of the most important and common minerals in your body. While most of your calcium is stored in your bones, you need calcium in your blood as well. Blood calcium is essential for proper functioning of your nerves, muscles and heart.

What is a comprehensive metabolic panel used for?

Your provider might order a CMP for:

• Diagnosis. A CMP can help your provider diagnose certain medical conditions.
• Screening. “Screening” means attempting to find health issues in the early stages, before you have symptoms. Providers often use a CMP as a part of routine health checkups.
• Monitoring. If you have certain medical conditions, a CMP can help your provider determine if your treatment is working. CMPs can also help check for side effects of certain medications, especially those that affect your liver or kidneys.

Why do I need a comprehensive metabolic panel?

A healthcare provider might order a CMP if:

• You’re experiencing symptoms related to kidney, liver and/or metabolism issues.
• You’re experiencing a general symptom, such as fatigue. A CMP can help determine or rule out certain causes of a common symptom.
• You had a prior test result that was abnormal. Your provider may want to test again to see if there’ve been any changes.
• You’re taking a treatment for a medical condition. Your provider may test to see if the treatment is working.
• You’re starting a new medication that can affect your kidney or liver function.

How does a comprehensive metabolic panel work?

For a CMP test, your healthcare provider collects a sample of your blood and sends it to a pathology lab for testing. The lab measures levels of proteins, enzymes, electrolytes, minerals and other substances in your blood.

Do I need to fast for a comprehensive metabolic panel (CMP)?

Maybe. Sometimes, providers ask you to avoid eating or drinking (fast) for 10 to 12 hours before a CMP. It might be helpful to schedule your test first thing in the morning, so you can eat right afterward. Your healthcare provider will give you specific instructions when they order the test for you.

What should I expect during a CMP blood test?

To get a blood sample for a CMP test, you’ll have a blood draw at your provider’s office or a lab. You’ll sit in a chair and a phlebotomist will:

1. Check your arms for an easily accessible vein. This is usually in the inner part of your arm on the other side of your elbow.
2. Clean and disinfect the area.
3. Insert a small needle into your vein to take a blood sample. This may feel like a small pinch.
4. Collect a sample of blood in a test tube.
5. Remove the needle and hold a cotton ball or gauze on your arm to stop any bleeding.
6. Place a bandage over the site.

The entire procedure usually takes about five to 10 minutes.

What are the risks of a comprehensive metabolic panel blood test?

There’s usually very little risk involved in getting blood tests, which is why they’re so common. There’s always a slight risk of infection any time something pierces your skin. You may have slight tenderness or a bruise at the site of the blood draw. This usually clears up in a few days to a week.

How do I read the results of a comprehensive metabolic panel (CMP)?

Once your CMP results are back, your provider will share them with you, or they might appear in your electronic health record. The results may appear as a list or a table.

These might seem like a confusing list of numbers and abbreviations. But if you know what you’re looking at, it can make it easier to read. In general, comprehensive metabolic panel results usually provide:

• The name of the blood test or what was measured in your blood (like BUN, calcium or ALT).
• The number or measurement of your blood test result.
• The unit of measure for that test, for instance, mg/dL (milligrams per deciliter). This is how much of the substance there is in a certain volume of blood.
• The normal range for that test. These can differ slightly by lab, so be sure to only compare your number to the one given on your results for that specific test.
• A flag or note if your result is higher or lower than the expected range. Sometimes, your result will appear in red if it’s out of the expected range. It may also note if it’s in the normal range.

When should I know the results of a comprehensive metabolic panel?

In most cases, you should have your CMP test results within one to two business days, though it could take longer.

What happens if the results of a CMP are abnormal?

If any of the CMP results are out of the range given by the lab, it could indicate:

• Liver disease.
• Kidney disease.
• Diabetes. Elevated fasting blood glucose is often a sign of Type 2 diabetes. Very high glucose levels, whether fasting or not, usually indicate Type 1 diabetes.
• High blood pressure (hypertension).

Keep in mind that if one of your CMP results is abnormal, it doesn't necessarily mean that you have a medical condition that’s causing it. Other factors, such as diet, certain medications and health conditions, can affect your test results.

If you have an abnormal result, your healthcare provider might order additional tests to confirm or rule out a specific diagnosis. If you have questions about your results, don’t be afraid to talk to your provider.

When should I call my doctor?

Contact your healthcare provider if you have any questions about a CMP test or its results.