Low Urea: Causes, Symptoms, Tests, Treatment and Tips

It is a waste product of the digestive system after eating protein.

The BUN (blood urea nitrogen) or urea nitrogen test shows the amount of urea in your blood.

Urea is generally a safe way to remove excess nitrogen from the body. Urea comes from dietary protein and tissue protein turnover.

Human bodies produce approximately 12 grams of urea per day in a regular diet.

However, most of the area, which equates to approximately 10 grams per day, is flushed out by the kidneys. A small amount of urea can also be lost through the intestine, skin, and lungs.

For example, a large amount of urea can be removed through your sweat when you exercise.

When doctors test your BUN numbers, they look for the balance between urea production in the liver and the breakdown of urea in the kidneys.


That is why these tests are done to assess the health of your kidney and liver. In some cases, testing creatinine levels is a better indicator of kidney function.

This is because BUN is more likely to be affected by dietary and physiological conditions that are not necessarily related to kidney function.

The liver releases urea into the bloodstream and carries it to the kidney, concentrated in the urine for excretion by the kidney.

High serum urea level indicates that the kidney is not working correctly, leading to impaired kidney function and decreased urinary urea excretion, leading to increased serum urea level.

However, low urea is generally not something to worry about.

Causes of low urea

The causes of low urea levels are:

  • Starvation.
  • Low protein diet.
  • Malnutrition.
  • Overhydration – Overhydration thins the blood, causing urea concentrations to drop and ions.
  • Low protein intake: Proteins are our primary nitrogen source, as they are made up of amino acids, starting with a group containing nitrogen.
  • Steroids
  • Pregnancy.
  • Old age.
  • I was having too much antidiuretic hormone (called ADH). This again causes the blood volume to increase due to water retention.
  • Liver disease: Urea is produced by multiple processes, including transamination (when amino acids are converted to others).

Most human transamination occurs in the liver, where many enzymes are found. When the liver is damaged somehow, transamination occurs less or more slowly.


Urea nitrogen is an element that can allow the diagnosis of possible kidney infection if this is the case.

Symptoms that can be signs that something is wrong with your kidneys are:

  • Change in the amount of urine.
  • Urine that is foamy, bloody, discolored, or brown.
  • Pain when urinating
  • Swelling in the arms, wrists, legs, ankles, around the eyes, face, or abdomen.
  • Restless legs during sleep.

Treatment of low urea

A proportion below the normal range of urea nitrogen could mean liver disease, malnutrition, or another cause; therefore, treatment will be applied based on the underlying cause or condition.

It is, therefore, crucial that when a low level of urea nitrogen is detected, the doctor is consulted to be treated and receive the indicated treatment.

BUN tests

Why is the BUN test done?

Blood urea nitrogen (BUN) and creatinine tests can be used together to find the BUN-creatinine ratio. A BUN to creatinine ratio can help your doctor detect problems, such as dehydration, that can cause abnormal BUN and creatinine levels.

A blood urea nitrogen (BUN) test is done to:

  • See if your kidneys are usually working.
  • See if your kidney disease is getting worse.
  • See if your kidney disease treatment is working.
  • Check for severe dehydration: Dehydration usually causes higher BUN levels than creatinine levels. This causes a high ratio of BUN to creatinine.

How do I prepare for the test?

Before the blood test, tell your doctor what medications you are taking. If any of them can alter the test result, your doctor may ask you to stop taking them for some time.

If you only get a BUN test, you can eat and drink. But if you have other blood tests, your doctor may give you instructions that may include fasting before the test.


The BUN (blood urea nitrogen) will return to normal with rehydration if the underlying kidney function is normal. In other words, if you have a regular BUN and are dehydrated long enough, the BUN will go up, and then the BUN will go down if you restore regular hydration.

If you have regular hydration and consume more water, the BUN and, more importantly, sodium can be removed, which can affect your brain and cause seizures.