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CHEM-7


Alternative names

CHEM-7 is a group of 7 chemical tests performed on serum (the portion of blood without cells).

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:
The area is cleaned with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test

Fast for 8 hours before the test.

Infants and children:
The preparation you can provide for this test depends on your child's age, previous experience, and level of trust. For general information regarding how you can prepare your child, see the following:
  • Infant test or procedure preparation (birth to 1 year)
  • Toddler test or procedure preparation (1 to 3 years)
  • Preschooler test or procedure preparation (3 to 6 years)
  • Schoolage test or procedure preparation (6 to 12 years)
  • Adolescent test or procedure preparation (12 to 18 years)

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

Blood chemistry measures the levels of a number of chemical substances that are released from various tissues in the body. The amounts of these chemicals in the blood may reflect abnormalities in the tissues secreting them.

Normal Values

The measured chemicals with their normal reference intervals are:
  • BUN (blood urea nitrogen): 7 to 20 mg/dl
  • Serum chloride : 101 to 111 mmol/L
  • CO2 (carbon dioxide): 20 to 29 mmol/L
  • Creatinine : .8 to 1.4 mg/dl
  • Glucose test : 64 to 128 mg/dl
  • Serum potassium : 3.7 to 5.2 mEq/L
  • Serum sodium : 136 to 144 mEq/L

Key to abbreviations:

  • L = liter
  • dl = deciliter = 0.1 liter
  • mg = milligram
  • mmol = millimole
  • mEq = milliequivalents

What abnormal results mean

See the individual tests.

What the risks are

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)
  • Multiple punctures to locate veins

Special considerations

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Update Date: 8/7/2003

Irfan A. Agha, M.D., Department of Medicine, Renal Division, St. Louis University, St. Louis, MO. Review provided by VeriMed Healthcare Network.

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Last updated: Tue, 06 Jan 2009 00:20:03 GMT
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