Analysis of blood chemistry can provide important information about the function of the kidneys and other organs. This common panel of blood tests measures levels of important electrolytes and other chemicals, including the following.
Glucose, or blood sugar, is broken down in the body's cells to provide energy. Elevated levels may be caused by diabetes or medications such as steroids.
Sodium levels in the blood represent a balance between sodium and water intake and excretion. Abnormal blood levels of sodium may indicate heart or kidney dysfunction or dehydration.
Potassium plays a vital role in regulating muscle activity, including contraction of the heart. Kidney failure as well as vomiting or diarrhea may lead to abnormal levels.
Chloride levels may rise and fall in parallel with sodium levels to maintain electrical neutrality. Several disorders may alter chloride levels, including kidney dysfunction, adrenal disease, vomiting, diarrhea, and congestive heart failure.
Carbon dioxide (CO2) acts as a buffer system to help maintain the acid-base balance of the blood. Respiratory disease, kidney disorders, severe vomiting, diarrhea, and very severe infections can produce abnormal levels.
Blood urea nitrogen (BUN) provides a rough measurement of the glomerular filtration rate, or the rate at which blood is filtered across small blood vessels in the kidney. A high BUN level may indicate kidney dysfunction.
Creatininewhich is a breakdown product of creatine, an important component of muscleis excreted exclusively by the kidneys. The serum creatinine level is considered the most sensitive blood test of kidney function.
Purpose of Blood Chemistry Screen
- To provide general information about how your body is functioning
- To screen for a wide range of problems, including kidney, liver, heart, adrenal, gastrointestinal, endocrine, and neuromuscular disorders
- To monitor people who have hypertension (high blood pressure) or hypokalemia (low levels of potassium)
- To detect problems with the way your body is working
- To measure chemical substances in the blood
Who Performs Blood Chemistry Screen
- A doctor, a nurse or a lab technician draws the blood sample.
Special Concerns about Blood Chemistry Screen
- A variety of medications can alter levels of electrolytes, blood urea nitrogen, and creatinine and interfere with the results of this test.
- Excessive ingestion of licorice or accidental consumption of ethylene glycol or methyl alcohol can affect acid-base balance and alter carbon dioxide levels.
- A diet rich in meats can cause transient elevations of serum creatinine.
- A high-protein diet, gastrointestinal bleeding, or dehydration elevates blood urea nitrogen levels, while a low-protein diet or overhydration tends to lower them.
Before Blood Chemistry Screen
- Report to your doctor any medications, herbs, or supplements you are taking. You may be advised to discontinue certain of these agents before the test.
- Avoid a diet rich in meats before a blood urea nitrogen test.
- No special precautions are needed before testing for sodium, potassium, chloride, carbon dioxide, or creatinine.
- Do not drink alcohol before this test.
What You Experience
- A sample of your blood is drawn from a vein, usually in your arm, and sent to a laboratory for analysis.
Risks and Complications of Blood Chemistry Screen
- There are no risks or complications associated with this test.
After Blood Chemistry Screen
- Immediately after blood is drawn, pressure is applied (with cotton or gauze) to the puncture site.
- Resume your normal diet and any medications that were withheld before the test, according to your doctor’s instructions.
- Blood may collect and clot under the skin (hematoma) at the puncture site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
Blood Chemistry Screen Results
- Your blood sample is sent to a laboratory for analysis. The doctor will review the results for evidence of kidney disease or another disorder.
- A blood chemistry screen is commonly used as an initial test to indicate potential health problems. Abnormal results often necessitate additional tests to establish a diagnosis.
- If an abnormality is found and the doctor can make a definitive diagnosis, appropriate treatment will be initiated.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media