A blood sample is needed. Most of the time blood is typically drawn from a vein located on the inside of the elbow or the back of the hand.
How to prepare for the test
You should not eat or drink for 8 hours before the test.
How the test will feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the test is performed
This test is done to evaluate:
Blood acid/base balance
Blood sugar levels
In some cases, the test also is used to check blood levels of calcium and a protein called albumin.
The following are normal ranges for the blood chemicals tested:
BUN: 7 to 20 mg/dL
CO2 (carbon dioxide): 20 to 29 mmol/L
Creatinine: 0.8 to 1.4 mg/dL
Glucose: 64 to 128 mg/dL
Serum chloride: 101 to 111 mmol/L
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
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What abnormal results mean
Abnormal results can be due to a variety of different medical conditions, including kidney failure, breathing problems, diabetes or diabetes-related complications, and medication side effects. Talk to your doctor about the meaning of your results from each test.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.