Blood Urea Nitrogen (BUN) Test

The Blood Urea Nitrogen (BUN) test is a laboratory test used to measure the levels of urea nitrogen in the blood. Urea nitrogen is a waste product that occurs in the blood when the body breaks down protein.

Purpose of the Test

The BUN test is used to:

• Evaluate kidney function and diagnose kidney disease or damage
• Monitor the effectiveness of dialysis in patients with kidney failure
• Check for dehydration or bleeding in the gastrointestinal tract
• Monitor the effects of certain medications on the kidneys

How the Test is Performed

A blood sample is drawn from a vein, usually in the arm. The sample is then sent to a laboratory for analysis.

What the Results Mean

The normal range for BUN levels is typically between 6 and 24 milligrams per deciliter (mg/dL). Abnormal results may indicate:

• Kidney disease or damage, which can cause elevated BUN levels
• Dehydration, which can cause elevated BUN levels
• Bleeding in the gastrointestinal tract, which can cause elevated BUN levels
• Malnutrition or starvation, which can cause low BUN levels

Risk Factors and Complications

Risk factors for abnormal BUN results include:

• Kidney disease or damage
• Dehydration
• Bleeding in the gastrointestinal tract
• Certain medications, such as antibiotics and diuretics

Complications of the BUN test are rare but may include:

• Bleeding or bruising at the needle site
• Infection at the needle site
• Fainting or dizziness due to blood loss

Preparation and Aftercare

No special preparation is typically required for a BUN test. However, patients may be asked to:

• Fast for a certain period before the test
• Avoid certain medications or foods that can affect the results

After the test, patients can usually resume their normal activities. The results of the BUN test are typically available within a few hours to a few days.