BUN stands for blood urea nitrogen. Urea nitrogen is what forms when protein breaks down.
A test can be done to measure the amount of urea nitrogen in the blood.
Blood urea nitrogen
How the test is performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
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, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to prepare for the test
Many drugs affect BUN levels. Before having this test, make sure the health care provider knows which medications you are taking.
Drugs that can increase BUN measurements include:
- Amphotericin B
- Aspirin (high doses)
- Chloral hydrate
- Polymyxin B
- Thiazide diuretics
Drugs that can decrease BUN measurements include:
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
The BUN test is often done to check kidney function.
7 - 20 mg/dL. Note that normal values may vary among different laboratories.
What abnormal results mean
Higher-than-normal levels may be due to:
- Congestive heart failure
- Excessive protein levels in the gastrointestinal tract
- Gastrointestinal bleeding
- Heart attack
- Kidney disease, including glomerulonephritis, pyelonephritis, and acute tubular necrosis
- Kidney failure
- Urinary tract obstruction
Lower-than-normal levels may be due to:
- Liver failure
- Low protein diet
Additional conditions under which the test may be done include:
- Acute nephritic syndrome
- Alport syndrome
- Atheroembolic kidney disease
- Dementia due to metabolic causes
- Diabetic nephropathy/sclerosis
- Digitalis toxicity
- Generalized tonic-clonic seizure
- Goodpasture syndrome
- Hemolytic-uremic syndrome (HUS)
- Hepatokidney syndrome
- Interstitial nephritis
- Lupus nephritis
- Malignant hypertension (arteriolar nephrosclerosis)
- Medullary cystic kidney disease
- Membranoproliferative GN I
- Membranoproliferative GN II
- Type 2 diabetes
- Prerenal azotemia
- Primary amyloidosis
- Secondary systemic amyloidosis
- Wilms' tumor
What the risks are
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.
Other risks are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
For people with liver disease, the BUN level may be low even if the kidneys are normal.
Molitoris BA. Acute kidney injury. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 121.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. ©1997-2013 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
Cortisone Injections for Tendonitis: A Good Idea?
What's Really Causing Your Foot Pain?
What Migraine Stage Are You Experiencing?
Chelation Therapy for Arthritis: Get the Facts
How to Treat 5 Different Types of Migraines
Sign Up for Free Newsletters
Ask Your Doctor the RIGHT Questions!
the most from your doctor visit.
Emailed right to you!
The Ask Your Doctor email series
may contain sponsored content.
18+, US residents only please.
Explore Original Articles About...
Get the MOST from QualityHealth
- Top Searches
- 1. Arthritis Management: Nature Heals
- 2. 5 Digestive To-Dos
- 3. Men: Should You Shave It or Leave It?
- 4. Today's Top Fitness Trends
- 5. Sugar and Osteoarthritis : The Link
- 6. Can't Afford Your Hospital Bills?
- 7. Stay Energized All Day Long
- 8. Phobias: Who Has Them and Why?
- 9. What If Your EpiPen Fails?
- 10. 5 Costly Medical Billing Mistakes
- 1. Ice Falls Can Cause Serious Injuries
- 2. Can Inactivity Act Like a Disease?
- 3. Kale Snack Recipe for Diabetics
- 4. How Running Affects Arthritis
- 5. Sugar and Your Immunity System
- 6. Do Weight Loss Supplements Work?
- 7. 5 Super Foods for Spring
- 8. The Hazards of Reusable Bags
- 9. How to Avoid Ingrown Hairs
- 10. Health Tip: Constantly Change Shoes
- 1. 4 Common Treatments for Epilepsy
- 2. What Does a Urogynecologist Do?
- 3. GERD Without Heartburn? It's Possible
- 4. Graston Technique: Can It Work on You?
- 5. Music Therapy Can Help Autism
- 6. 8 Ways to Fight MS-Related Fatigue
- 7. Can You Still Bleed After Menopause?
- 8. Be Your Own Health Care Advocate
- 9. Why Is Syphillis on the Rise?
- 10. Ideal Weight vs. Happy Weight
The material on the QualityHealth Web site is for informational purposes only, and is not a substitute for medical advice, diagnosis, or treatment provided by a physician or other qualified health provider. See additional information.