Ammonia levels, risks, and hyperammonemic crises

What can cause high ammonia levels?

Any increase in ammonia levels can be dangerous

Your body makes ammonia as a waste product when it digests protein. Usually, your body changes ammonia to something called urea, which leaves the body as part of urine. In people with UCDs, a part of the urea cycle that changes ammonia into urea is missing or does not work properly. This causes ammonia to build up in the bloodstream, which can be life-threatening.

The normal blood ammonia range is 11 to
32 µmol/L, but normal ranges may vary slightly depending on the laboratory performing the test.

The normal blood ammonia range is 11 to
32 µmol/L, but normal ranges may vary slightly depending on the laboratory performing the test.

Why is too much ammonia bad?

Gauging ammonia levels is key to UCD treatment

Any increase in ammonia, also known as hyperammonemia, is serious and can lead to brain damage over time. Ammonia is toxic, and having too much in the body can have serious consequences. Increased ammonia levels can affect memory, behavior, learning abilities, brain development, and ability to think clearly, and they can lead to life-threatening hyperammonemic crises (HACs) if not managed. An HAC requires immediate medical attention and can cause coma and even death if not treated appropriately.

Learn about important key terms in ammonia level management.>

What are the symptoms of increased ammonia levels?

Orange brain graphic with purple circles

Symptoms can range from mild to severe depending on the type of UCD, the level of ammonia, and how long ammonia has been elevated. People with UCDs may experience any of these signs and symptoms of increased ammonia:

  • Confusion and/or feeling dizzy
  • Headaches or migraines
  • Little or no appetite
  • Trembling or shaking out of control
  • Mood or behavior changes
  • Seizures
  • Hallucinations
  • Emotional or personality changes

If you or a loved one experiences any of these symptoms, talk to a doctor as soon as possible.

Other serious issues that can occur when ammonia levels have remained increased over
time include:

  • Learning difficulties
  • Brain damage
  • Coma
  • Death

Sometimes, people with UCDs and increased ammonia levels do not have any symptoms, which can be dangerous. While HACs are known for their clear and damaging effects, it’s important to know that even slightly raised ammonia levels with no symptoms can also lead to brain damage. Work with your or your loved one’s healthcare team to manage ammonia levels. Learn more about current UCD treatment strategies.>

If you or a loved one is experiencing symptoms or needs help managing a UCD, talk to a doctor as soon as possible.

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Sources

  1. 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.
  2. National Library of Medicine, National Institutes of Health and Human Services. Ammonia blood test. Accessed February 25, 2022. https://medlineplus.gov/ency/article/003506.htm#:~:text=The%20normal%20range%20is%2015,of%20your%20specific%20test%20results
  3. Weiner ID, Mitch WE, Sands JM. Urea and ammonia metabolism and the control of renal nitrogen excretion. Clin J Am Soc Nephrol. 2015;10(8):1444-1458.
  4. Enns GM, Porter MH, Francis-Sedlak M, Burdett A, Vockley J. Perspectives on urea cycle disorder management: results of a clinician survey. Mol Genet Metab. 2019;128(1-2):102-108.
  5. Gropman AL, Prust M, Breeden A, Fricke S, VanMeter J. Urea cycle defects and hyperammonemia: effects on functional imaging. Metab Brain Dis. 2013;28(2):269-275.
  6. Gerstein MT, Markus AR, Gianattasio KZ, et al. Choosing between medical management and liver transplant in urea cycle disorders: a conceptual framework for parental treatment decision-making in rare disease. J Inherit Metab Dis. 2020;43(3):438-458.