A blood urea nitrogen test detects and measures the amount of urea nitrogen present in your blood. This test is performed to determine and monitor the overall health and functioning of your kidneys. For the unversed, urea nitrogen is a waste product that gets collected in the liver when your body is done breaking down the proteins. Our kidneys function in a way to filter out this waste from the protein which is then flushed out of our body when we urinate.
The amount of blood urea nitrogen in your blood tends to increase when your kidneys or liver have suffered damage. One of the clear signs of a possible kidney or liver problem is when an unusually high amount of urea nitrogen is measured in the blood.

Blood Urea Nitrogen (BUN) Overview 

A blood urea nitrogen test detects and measures the amount of urea nitrogen present in your blood. This test is performed to determine and monitor the overall health and functioning of your kidneys. For the unversed, urea nitrogen is a waste product that gets collected in the liver when your body is done breaking down the proteins. Our kidneys function in a way to filter out this waste from the protein which is then flushed out of our body when we urinate.
The amount of blood urea nitrogen in your blood tends to increase when your kidneys or liver have suffered damage. One of the clear signs of a possible kidney or liver problem is when an unusually high amount of urea nitrogen is measured in the blood.
 

Why is Blood Urea Nitrogen (BUN) Test Performed?
 

A blood urea nitrogen test is one of the basic tests a doctor orders when they are assessing your overall health. Since it is a common yet potent measure to detect any possible liver or kidney problems, almost every preventive health check-up or basic metabolic check-up has a blood urea nitrogen test included in the package.
 

Your doctor may also order to get a blood urea nitrogen test done if you have or show any of the kidney or liver disease risk factors. Although there are no clear early signs of kidney disease, some risk factors expose you to an increased risk of getting one. Here are the risk factors or conditions where your doctor would advise to go for a blood urea nitrogen test:
 

• Diabetes
• Hypertension
• Coronary artery disease (CAD) or heart disease
• Family history of kidney disorder

Your doctor is highly likely to order a blood urea nitrogen test if you show the following symptoms:
 

• Unexplained fatigue
• Frequent or too little urinatio 
• Passing discoloured urine or having unusual consistency like foamy, bloody, or brown-coloured
• Unusual swelling around eyes, face arms, abdomen, legs, or feet
• Nausea, vomiting, or loss of appetite
• High blood pressure

A blood urea nitrogen test is done in the following cases:
 

• If your doctor is suspicious of your symptoms that point towards a kidney disease ordamage
• If your kidney function needs to be evaluated, particularly in case of chronic health issues like diabetes or high blood pressure
• If you’re undergoing haemodialysis or peritoneal dialysis, a blood urea nitrogen test is performed to measure and monitor the effectiveness of dialysis
• If your doctor wants to assess you for other health conditions like liver damage, urinary infections or obstructions, GI bleeding, and congestive heart failure

How to Prepare for & What to Expect During a Blood Urea Nitrogen (BUN) Test?
 

If you're going to get a blood sample drawn only for the blood urea nitrogen test, there are no fasting or dietary restrictions you need to follow. You can eat or drink normally before going for the rest. If there are any additional tests to be done along with a blood urea nitrogen test, your doctor will advise you on the requirement for fasting. However, consumption of alcohol before the blood test is a strict no.

It is important to tell your doctor if you’re taking any over-the-counter medications or health supplements as some of them may affect your blood urea levels. Telling this information to your doctor will help them review your test results accordingly.

The blood urea nitrogen test is a simple test that only requires a vial of blood to be drawn. Your healthcare provider or the phlebotomist will make you sit in a chair and insert a thin needle into your vein to draw the blood sample into the attached vial. The overall test only takes about 5-10 minutes and there are no aftermaths involved. You will only feel a little needle prick. Any bruises on the arm, if occurred, will go away on their own within a few hours to 1-2 days.
 

Understanding Your Blood Urea Nitrogen (BUN) Test Results
 

Blood urea nitrogen test results are measured in milligrams per decilitre (mg/dl). However, normal BUN values aren’t the same for everyone, they tend to differ based on a person’s age, gender, and existing medical conditions. Also, each laboratory has different sets for normal ranges based on their geographic locations and benchmark values.
 

Generally, normal BUN levels have the following reference ranges:
 

• adult men: 8 to 24 mg/dL
• adult women: 6 to 21 mg/dL
• children 1 to 17 years old: 7 to 20 mg/dL

Higher levels of blood urea nitrogen test are an indicator of the following conditions:
 

• Heart diseases
• Increased risk of a congestive heart failure
• Recent episode of heart attack
• Dehydration
• High protein levels
• GI bleeding
• Kidney disease or failure
• Urinary tract obstruction
• Shock or stress

Also, lower levels of blood urea nitrogen are indicative of:
 

• Liver failure
• Under-nourishment
• Overhydration/water retention
• Severe lack of protein in the diet

Depending on the BUN test results, your doctor may order some more tests like creatinine or GFR (Glomerular Filtration Rate) to reach a diagnosis. However, to attain and maintain healthy BUN levels, adequate hydration is extremely important. Those with higher blood urea nitrogen levels should go for a low-protein diet to bring down the levels. Abnormal blood urea nitrogen levels aren’t always suggestive of kidney disease or failure.

Some factors affecting your urea nitrogen levels without posing a direct threat to your health include dehydration, pregnancy, high or low protein intake, steroids, and ageing.