What Is Urea?

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Urea is an organic compound formed when nitrogen and protein break down and is the main component of human urine. It has many uses, including in fertilizer and other industrial processes and in creams that treat skin disorders, such as psoriasis, eczema, atopic dermatitis, and ingrown nails.

Some individuals have urea cycle disorders that inhibit them from properly disposing of waste, which can lead to neurological symptoms.

Learn more about how the body produces urea, why it is important, its various uses, and the disorders that disrupt its production.

Healthcare provider testing blood for urea

Md Zakir Mahmud / Getty Images

How Is Urea Produced?

Urea is produced through the urea cycle, a biochemical process that the body uses to eliminate waste. Proteins must be broken down regularly from excess protein in the diet or old cells that need replacing. The breakdown of protein creates a toxic substance called ammonia, which humans cannot safely excrete (eliminate).

Instead, we convert ammonia into less toxic urea through a multistep process involving several different proteins. This process occurs in the liver; then, urea is released into the bloodstream, where it travels to the kidneys and is finally excreted as urine.

Blood Urea Nitrogen (BUN)

Blood urea nitrogen (BUN) is a common blood test that can evaluate kidney function. This test measures the amount of nitrogen from urea in the blood, indicating the levels of waste from cell metabolism. Elevated or decreased BUN can signify several conditions, including diseases that affect the kidneys or the liver.

Other factors, such as medications, diet, and hydration, can impact BUN levels. Therefore, it is important to look at BUN levels in conjunction with other tests, such as creatinine (waste level tests), to get an accurate picture of kidney function.

Urea Cycle Disorders

Sometimes, one or more defects can occur in the proteins involved in the urea cycle, resulting in a urea cycle disorder. When this happens, the body cannot properly process the toxic ammonia waste produced from protein breakdown.


Urea cycle disorders are typically diagnosed in infancy or childhood and result from a genetic defect inherited from one or both parents. An individual with a urea cycle disorder may have defects in one of the six enzymes or two transport proteins involved in the urea cycle.


The buildup of ammonia in the body can lead to mild-to-severe symptoms, depending on which enzymes are impacted. The symptoms of urea cycle disorders most often affect the brain and nervous system and may be apparent in infancy or early childhood depending on the severity of the defects. Symptoms that may arise in early infancy include:

  • Sleepiness or lethargy
  • Vomiting or refusal to eat
  • Low body temperature (hypothermia)
  • Seizures
  • Muscle rigidity (posturing)
  • Coma
  • Respiratory failure

In less severe cases, ammonia levels do not rise as quickly, and symptoms may not be apparent until several months or years after birth. In these cases, symptoms may include:

  • Behavioral or psychiatric issues
  • Seizures
  • Avoidance of protein foods
  • Nausea and vomiting


Urea cycle disorders are diagnosed by a healthcare provider, who will review your or your child's symptoms and medical history. One of the hallmark signs of a urea cycle disorder is hyperammonemia (high ammonia levels).

Other blood tests and genetic tests will confirm a suspected urea cycle disorder if hyperammonemia is identified. Some congenital (found-at-birth) defects associated with a urea cycle disorder are tested during routine newborn screening, though not all.


When diagnosed, the high ammonia levels must be removed from the body using dialysis (a blood-filtering procedure). Further treatment depends on the severity of the disorder, age, coexisting medical conditions, and other factors.

Nutrition support and dietary modifications are usually necessary to manage urea cycle disorders long term. Your healthcare provider will likely recommend a low-protein diet to decrease the metabolic waste produced in the body and vitamin and mineral supplements to ensure nutritional adequacy. 

For some, a liver transplant may be an option to cure a urea cycle disorder completely. This will not reverse any existing neurological damage caused by hyperammonemia but can help an individual lead a more normal healthy life.

Urea Uses

Outside the human body, urea has several uses. It is used in agriculture as a fertilizer due to its high nitrogen content. It also has uses in other industries and can be found in animal feed, barbituric acid, cold packs, and other products.

Urea is also widely used in dermatology as a topical cream for treating skin conditions such as eczema, psoriasis, atopic dermatitis, ichthyosis, xerosis, seborrheic dermatitis, and others. This is in part because urea is what’s known as a hygroscopic molecule, meaning it is capable of absorbing water.

Urea also has antimicrobial properties and improves skin barrier function. It is one of the most common moisturizing agents and has few mild side effects, making it a safe option for treating many skin conditions that result in scaly, dry skin.


Urea is an organic compound that is the main component of urine. It is produced from the breakdown of proteins into ammonia to create a less toxic substance that the body can eliminate.

Specific genetic defects can cause urea cycle disorders, causing a buildup of ammonia that can lead to severe symptoms, such as neurological damage. Urea has other uses outside the body, such as in nitrogen-rich fertilizer in agriculture and moisturizing topical cream in dermatology. 

A Word From Verywell

It can be challenging to receive a urea cycle disorder diagnosis for yourself or your child. But know that one can live a long, happy life with proper disease management.

Frequently Asked Questions

  • What are the symptoms of high urea?

    High urea, also known as uremia, can occur in chronic kidney disease and other conditions. Common symptoms may include cognitive issues, fatigue, shortness of breath, muscle cramps, nausea, vomiting, and weight loss. Contact your healthcare provider if you think you may have high urea levels. 

  • What causes urea?

    Urea is produced in the urea cycle, in which excess proteins from the diet or old cells are broken down into waste products. Ammonia is a toxic substance formed from the breakdown of proteins, which the body then converts to less toxic urea that it can eliminate.

  • Where is urea found?

    Urea is found in the urine, blood, and sweat of mammals. It is made in the liver from the breakdown of proteins and is carried through the bloodstream before being excreted as waste. Urea is also used in fertilizer and topical creams for treating skin conditions.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Wang H, Ran J, Jiang T. Urea. Subcellular Biochemistry. 2014:7-29. doi:10.1007/978-94-017-9343-8_2 

  3. Summar ML, Mew NA. Inborn errors of metabolism with hyperammonemia: Urea cycle defects and related disorders. Pediatric Clinics of North America. 2018;65(2):231-246. doi:10.1016/j.pcl.2017.11.004 

  4. Häberle J, Burlina A, Chakrapani A, et al. Suggested guidelines for the diagnosis and management of urea cycle disorders: first revision. J Inherit Metab Dis. 2019;42(6):1192-1230. doi:10.1002/jimd.12100

  5. Piquero-Casals J, Morgado-Carrasco D, Granger C, et al. Urea in dermatology: a review of its emollient, moisturizing, keratolytic, skin barrier enhancing and antimicrobial properties. Dermatology and Therapy. 2021;11(6):1905-1915. doi:10.1007/s13555-021-00611-y

By Rebecca Valdez, MS, RDN
Rebecca Valdez is a registered dietitian nutritionist and nutrition communications consultant, passionate about food justice, equity, and sustainability.