What Is Azotemia?

Medically Reviewed by Carmelita Swiner, MD on April 30, 2023
Written by WebMD Editorial Contributors
4 min read

Azotemia is a common health condition among older adults and people who are in the hospital. Around 8% to 16% of hospital admissions are due to azotemia. 

This condition occurs when your kidneys have been damaged by injury, disease, or medications, and they're unable to get rid of enough nitrogen waste in your body.

Your body forms urea (a waste product that's a major component of urine) when elements such as carbon, hydrogen, and oxygen combine with the nitrogen that’s produced by your liver. The urea then travels through your blood from the liver to the kidneys.

Your kidneys filter the blood, removing extra fluid and waste from your body to make urine. They also remove acid produced by your cells and help maintain your body’s balance of minerals, salts, and water.

Your kidneys receive about a quarter of the blood that your heart pumps in one minute (this is called cardiac output). This means they can be sensitive to any decrease in blood pressure.

If the pressure of the blood flowing through your kidneys drops, they filter less blood, or none at all. When this happens, waste products stay in the body. This buildup of blood urea nitrogen (BUN) and creatinine in the blood is called azotemia.

There are three types of azotemia:

1. Pre-renal azotemia. This is the most common form of azotemia. It’s the result of decreased blood flow to the kidneys. There are several conditions and diseases that can lead to slower blood flow:

  • Blood loss
  • Heart attack or heart disease
  • Liver failure
  • Severe dehydration
  • Infection
  • Use of some drugs like aspirin or ibuprofen 
  • Severe burns

2. Intrinsic azotemia. This type of azotemia typically occurs because of damage to the structure of your kidneys. The diseases and conditions that may result in damage to your kidneys include:

3. Post-renal azotemia. This usually happens when there's a blockage in the drainage tubes (known as ureters) that urine flows through. This could be due to diseases and conditions including:  

You may not notice symptoms of kidney problems like azotemia until it’s in a late stage. Some people have no signs or symptoms at all. Your doctor may learn that you have this condition while doing lab tests for other reasons.

Some possible symptoms of azotemia include:

  • Not urinating often (occasionally the amount of urine is normal, though)
  • Feeling tired
  • Feeling like you’re going to throw up (nausea)
  • Confusion
  • Weakness
  • Shortness of breath
  • Chest pain or pressure in your chest
  • Swelling in your legs, feet, or ankles because of fluid retention
  • Irregular heartbeat
  • In severe cases, coma or seizures

The toxic effects of nitrogen waste can lead to uremia. Uremia is the buildup of urea in the blood. This can cause:

  • Itching
  • Nausea
  • Vomiting
  • Damage to the brain
  • Weakness or numbness in your hands and feet ‌

It’s important to treat azotemia so that it doesn’t result in acute kidney failure or tissue death (acute tubular necrosis). Acute kidney failure can lead to:

  • Fluid buildup in your lungs, leading to shortness of breath
  • Chest pain, which happens if the lining that covers your heart becomes inflamed
  • Muscle weakness because your body’s fluids and electrolytes are not in balance
  • Permanent kidney damage, which requires either a kidney transplant or permanent dialysis
  • Death 

The blood urea nitrogen (BUN) test is a common blood test. Before the test, tell your doctor about any medications you’re taking. You might have to stop taking any that might affect the outcome of the BUN test. If your blood is only being tested for blood urea nitrogen, you won’t need to fast before the test. 

A healthcare professional will take a blood sample from a vein in your arm. The sample will be sent to a lab to be analyzed. A normal result is about 7 to 20 milligrams per deciliter. These ranges can vary depending on age and the reference range your lab uses. In azotemia, the BUN test result will be greater than 21 milligrams per deciliter.

High blood urea nitrogen can also be due to several other reasons, including:

Other tests that your doctor may recommend include:

It’s important to treat the condition before kidney damage happens. This usually requires a hospital stay. 

Your doctor will work to identify the underlying condition that’s causing your kidney problems. This may include the following treatments:

  • Intravenous (IV) fluids to increase fluid and blood volume
  • Medications to control potassium in your blood or to restore blood calcium levels
  • Dialysis to remove any toxins in your blood. This uses a machine to pump blood out of your body to filter it. The blood is then returned to your body.