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The basics of urea cycle disorder.

Urea cycle disorders (UCDs) are a group of inherited rare conditions where dangerous levels of ammonia build up in your body. Ammonia is very harmful, especially to the brain.

To understand UCD, it’s helpful to know about the normal urea cycle and how the body gets rid of ammonia.

  • You get protein into your body from the foods you eat.
  • The protein breaks down and your body uses what it needs.
  • When protein breaks down, nitrogen is released.
  • Nitrogen turns into ammonia.
  • Ammonia turns into urea in the liver.
  • Urea goes into the urine and the body gets rid of it.

With UCD, a protein that turns ammonia into urea doesn’t work the way it should. If ammonia can’t turn into urea, it stays in the body. The amount of ammonia builds up and is very harmful (toxic), especially to the brain.

There are a few different types of UCDs. UCD may be diagnosed in a newborn infant. A few days after birth, the baby may become very sluggish and lethargic. The baby may not feed well, throw up and have trouble breathing. This is an emergency. Doctors will check the level of ammonia in the baby’s blood. Sometimes UCDs aren’t found until a person is an adult. These are usually milder forms.

Hyperammonemia crisis

Ammonia levels can rise quickly with little warning. When they get too high, you can have a hyperammonemia crisis. This is always an emergency. Hyperammonemia crisis can lead to a coma and even death. Talk to your doctor about signs of hyperammonemia crisis. If you’re having any signs, go to an emergency room right away. It’s a good idea to call and let them know you are coming if you can. This gives them time to be ready for you. They’ll draw your blood and start treating you right away.

Ammonia levels can increase and lead to hyperammonemia crisis due to:

  • Viral infections
  • Physical or emotional stress 
  • Being dehydrated
  • Trauma or accident
  • Menstruation (having periods) for girls and women
  • Big changes in diet

Remember, any level of elevated ammonia, even if it’s not high enough to cause symptoms or a hyperammonemia crisis, can cause brain damage.

There is no cure for UCD, but by following a careful diet and keeping other healthy lifestyle habits, you can help control your UCD. Your doctor may also prescribe medications that help keep your ammonia levels lower

For more support and information, reach out to your CVS Specialty CareTeam or the following resources:

National Urea Cycle Disorders Foundation:

UCD Family:

Global Genes:

Rare Diseases Clinical Research Network:

UCD in Common:

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