A comprehensive metabolic panel (CMP) is a common group of blood tests that provides basic information about your health.
A comprehensive metabolic panel gives basic information about many health problems, including acute (short-term) or chronic (long-term) conditions. For this reason, a CMP can be a helpful diagnostic or monitoring tool.
A doctor might order a CMP as part of a routine physical. They may also order one if you have or they suspect you have any of the following conditions:
- Heart failure and/or heart rhythm problems
- Dehydration
- Diabetes
- Kidney disease
- Liver disease
- Seizures
- Problems with your glands, including your thyroid, parathyroid, or adrenal glands
- Nutritional deficiencies
The comprehensive metabolic panel measures the blood levels of 14 substances. The substances are:
- Glucose: Also called blood sugar, glucose is the primary fuel for most of your body’s cells. Levels that are too high or low can cause serious problems.
- Sodium, potassium, bicarbonate, and chloride: These four components are all electrolytes, which are charged mineral particles in your body. They play important roles in fluid regulation and muscle and nerve function.
- Calcium: The mineral is a major component of your bones. When dissolved in your blood, calcium is also an electrolyte important for muscle and nerves.
- Blood urea nitrogen (BUN) and creatinine: Urea and creatinine are two normal waste products your body produces. They are normally filtered out through the kidneys and into the urine, so they can be used to assess kidney function.
- Albumin and total protein: The main protein in your blood is albumin, a protein made in the liver. Total protein includes both albumin and some additional proteins made in your liver. Both tests are sometimes used to assess liver function, as well as some other issues.
- Alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate aminotransferase (AST), and bilirubin: ALP, ALT, and AST are all proteins made primarily in the liver, and bilirubin is a waste product of old red blood cells mainly broken down in the liver. These also give some basic information on the liver and sometimes other organs.
Your doctor may request a comprehensive metabolic panel during an in-office exam. If your provider wants you to have the CMP before or after your scheduled appointment, they’ll let you know when and where you can have the test done.
The doctor will typically ask you to fast before having your CMP. That means you can’t eat and can only drink water, usually at least eight hours before the test.
You can do the following to be prepared ahead of your blood test:
- Drink plenty of water before the test to make it easier for the person drawing the blood to find a vein.
- Check with your doctor to see if you should change any of your medications before the test. Most people can usually continue taking their medication as usual.
- Wear a short-sleeved shirt or a shirt with loose sleeves that will be easy for you to roll up for easy access to the veins in your arm.
- Bring your insurance card, if you have one, and your picture ID.
- Bring your doctor’s prescription for the test if you’re having it done at a test site rather than during an in-office exam.
A doctor or phlebotomist (a medical professional trained to draw blood) collects a small sample of your blood in a vial, which is then sent to a lab for analysis.
During the Test
You’re usually sitting in a chair for a blood test. It takes just a few minutes to complete.
Here’s how the blood draw usually works:
- The provider will wrap a tight band around your arm to help look for a good vein for the blood draw. You may need to pump your fist to help the vein pop out. Often, blood is drawn from a vein around the inside of your elbow, but other locations, like the back of your hand, can be used if needed.
- The provider will clean the area.
- The provider will insert the needle. You may feel a slight sting when the needle enters and exits your skin.
- The provider will collect the blood in a vial or tube. Depending on whether or not you’re having additional blood tests done, the provider might collect multiple samples.
- Once they’ve collected enough blood, your provider will remove the needle and cover the site with a small bandage.
After the Test
After the test, some people might feel a little dizzy, so try not to stand until ready. You should then be able to go about your everyday activities as usual.
Getting a comprehensive metabolic panel is generally safe. There may be some bleeding at the site, and sometimes a small bruise may form at the entry site. In rare cases, a blood vessel can burst and lead to a hematoma, which is when the skin becomes spongy and tender.
Infection rarely happens and shouldn’t be a risk factor if your provider uses proper techniques while collecting your blood. You should let your provider know where to avoid drawing blood, such as in scarred areas or areas with an active skin infection, to lower your risks.
Your blood sample will be sent to a laboratory for analysis. You should get your test results within a few days. The results may be available through an online patient portal or your doctor may call you about the results.
If any of your results come back too high or low, your doctor may want to do additional testing.
Interpreting Results
The results will list the findings of each of the 14 substances. Your doctor will assess them using established reference ranges. For example, a normal blood level range for potassium is between 3.5-5.0 milliequivalents per liter, but for sodium, the range is 136-145 milliequivalents per liter.
If your value is higher or lower than the expected range, it might indicate a problem, but not always. The following are some examples of some abnormalities you might see on a CMP:
- Glucose: If you fasted before the CMP and your glucose level is high, it might indicate diabetes. Glucose might be too low in someone who takes too much medication, like insulin, to treat diabetes.
- Sodium and potassium: Low levels of these can occur from diarrhea, kidney disease, or heart failure. Less commonly, sodium or potassium can be too high from dehydration or conditions related to the adrenal glands (glands located above the kidneys). If levels are very far from normal in either direction, it can cause life-threatening abnormal heart rhythms.
- Calcium: Too low or too high calcium levels might indicate bone disease, parathyroid (glands near the thyroid gland) disorders, and kidney disease. Extremely low calcium can cause symptoms like seizures and arrhythmias (irregular heart rhythms).
- BUN and creatinine: High levels might be a sign of kidney disease, though they might also indicate issues such as dehydration. These tests can be helpful in screenings for people at risk of kidney disease, such as people with diabetes.
- Albumin and total protein: If low, these might indicate issues like liver or kidney disease.
- ALT, AST, ALP, and bilirubin: If one or more of these is high, it may indicate liver damage, possibly from liver infection or liver cancer. High bilirubin might also indicate gallbladder disease or difficulty breaking down too many red blood cells.
Interpretation Challenges
Because the CMP measures so many substances, interpretation can be tricky. Some results might be quite straightforward, but other times it might be harder to know what to make of an abnormal value.
It’s important not to jump to conclusions if you see a number on a CMP that is out of the expected range. Sometimes, these reflect laboratory errors, such as a problem with how the blood sample was taken. If your results seem unusual, you might need to get retested to rule out any errors.
Other times, a certain value might be a little out of the normal range but not actually indicate a problem. Your doctor can help you interpret your tests based on your overall health.
A comprehensive metabolic panel (CMP) is a group of blood tests a doctor may order as part of a routine check-up or to help diagnose conditions. A CMP measures 14 substances in your blood, including glucose, calcium, and albumin. While levels that are too high or too low may indicate temporary or long-term medical conditions, not every value outside the “normal” range indicates a problem. Your healthcare provider can help you interpret your test results.
