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.

In a normal diet, human bodies produce approximately 12 grams of urea per day.

However, most of the urea, 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, when you exercise, a large amount of urea can be removed through your sweat.

When doctors test your BUN numbers , they are looking 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, which means that it is concentrated in the urine for excretion by the kidney.

High serum urea level indicates that the kidney is not working properly, 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 level are:

  • Starvation.
  • Low protein diet.
  • Malnutrition.
  • Overhydration – Overhydration thins the blood, causing not only urea concentrations to drop, but also ions.
  • Low protein intake: Proteins are our main source of nitrogen, as they are made up of amino acids, starting with a group that contains nitrogen.
  • Steroids
  • Pregnancy.
  • Old age.
  • 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 of human transamination takes place in the liver, where many enzymes are found. When the liver is damaged in some way, transamination takes place less or more slowly.


Urea nitrogen is an element that can allow the diagnosis of a 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

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

It is therefore important 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 working normally.
  • See if your kidney disease is getting worse.
  • See if your kidney disease treatment is working.
  • Check for severe dehydration : Dehydration usually causes BUN levels to rise more 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 a period of 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 normal BUN and are dehydrated long enough, the BUN will go up and then the BUN will go down if you restore normal hydration.

If you have normal hydration and consume more water, the BUN and more importantly sodium can be removed, which can result in affecting your brain and causing seizures.