Chem 7: Blood Chemistry Tests

What Your Basic Metabolic Panel Test Results Mean

Blood chemistry tests are often ordered prior to surgery to evaluate the general health status of a person. The panel of tests, commonly referred to as a Chem 7 because it looks at seven different substances in the blood, is also routinely performed after surgery to make sure the person is well in the days following their operation.

Vials in lab
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This test is known by multiple names—including a sequential multi-channel analysis with computer 7 (SMAC7) or metabolic 7—but most medical professionals refer to it as either a Chem 7 or basic metabolic panel (BMP). A comprehensive metabolic panel (CMP) similar but includes six additional tests.

The seven tests that comprise the Chem 7 panels are (by alphabetical order): 

  • Blood urea nitrogen (BUN)
  • Carbon dioxide
  • Creatinine
  • Glucose
  • Serum chloride
  • Serum potassium
  • Serum sodium

What to Expect

Your doctor may order the Chem 7 test several days before your procedure or just prior to undergoing surgery. For the test, blood will be drawn from a vein or taken from an intravenous (IV) line. The lab can usually return results very quickly.

When the results are returned, the lab report will provide reference ranges for each of the seven substances being tested. A result is considered normal if it falls between the high and low values in the range.

Anything below or above the reference range is considered abnormal, although there is some flexibility in the interpretation of the results based on your age, general health (including chronic medical conditions), and even location.

If values are "deranged" (meaning excessively high or excessively low), you may not be able to undergo surgery or require medical intervention before you can.

Depending on where you live in the world, the test results may be described differently.

In the United States, blood test results are typically described in standard metric values, such as milliliters (mL) or milligrams per deciliter (mg/dL). Internationally, they are often described in metric concentration values, such as millimoles per liter (mmol/L) or micromoles per liter (umol/L).

Blood Urea Nitrogen (BUN)

Blood urea nitrogen (BUN) is a measure of kidney function. It measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is made when protein is broken down by the kidneys. A high level may indicate that the kidneys are functioning less than normal.

The normal BUN values in adults are between:

  • 8 to 23 mg/dL (U.S.)
  • 2.9 to 8.9 mmol/L (international)

Carbon Dioxide (CO2)

This test measures the amount of carbon dioxide in the blood. Most carbon dioxide is present in the form of bicarbonate, which is regulated by the lungs and kidneys. The test result is an indication of how well the kidneys, and sometimes the lungs, are managing the bicarbonate in the blood.

The normal CO2 values for adults are between:

  • 22 to 28 mEq/L (U.S)
  • 22 to 29 mmol/L (international)

Creatinine

Creatinine is produced by the body during the process of normal muscle breakdown. High levels may indicate kidney impairment, low blood pressure, high blood pressure, or another condition.

Some medications can also cause a higher than normal level of blood creatinine. Low levels may be caused by late-stage muscular dystrophy, myasthenia gravis, or overhydration.

The normal creatinine values for adults are between:

    • 0.6 to 1.2 mg/dL (U.S.)
    • 7.0 to 17.6 umol/L (international)

Glucose

The blood glucose test is a measure of your blood sugar (glucose). High levels of glucose can indicate the presence of diabetes or another endocrine disorder.

Keep in mind that some medications and the timing of the test in relation to meals can radically alter the results. This is why the glucose test is usually done in a fasting state, particularly before surgery.

The normal glucose values for adults are between:

  • 70 to 110 mg/mL (U.S.)
  • 3.9 to 6.1 mmol/L (international)

Serum Chloride

The serum chloride (Cl) test measures the level of chloride in your blood. Chloride binds with electrolytes such as potassium and sodium and plays a role in maintaining the proper pH balance of the blood.

Chloride levels can vary widely if a person is dehydrated or overhydrated. It can be a sign that the kidneys are not functioning properly. Heart failure and endocrine problems can also contribute to abnormal Cl results.

The normal serum chloride values in adults are between:

  • 96 to 106 mEq/L (U.S.)
  • 96 to 106 mmol/L (international)

Serum Potassium

The serum potassium (K) test shows the level of potassium in the blood. Potassium plays an important role in muscle contractions and cell function. Both high and low levels of potassium can cause problems with the rhythm of the heart, so it is important to monitor the level of potassium before and after surgery.

People who take diuretics regularly may require regular blood tests to monitor potassium levels, as some diuretics can cause the kidneys to excrete too much potassium.

The normal serum potassium values for adults is between:

  • 3.5 to 5.0 mEq/L (U.S.)
  • 3.5 to 5.1 mmol/L (international)

Serum Sodium

The serum sodium (Na) test measures the amount of sodium in the blood. The kidneys work to excrete any excess sodium that is ingested in food and beverages. Sodium levels can fluctuate with dehydration or overhydration, diarrhea, endocrine disorders, trauma, bleeding, and other causes.

The normal serum sodium values for adults are between:

  • 136 to 142 mEq/L (U.S.)
  • 135 to 145 mmol/L (international)

A Word From Verywell

Chem 7 is an invaluable blood panel that poses little risk. You may have slight pain or bruising at the site where blood is drawn, but most symptoms go away quickly. If the test is ordered several days in advance of surgery, you may be required to fast. If unsure, double-check with your doctor.

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