A UCD (which is a shortened name for a ‘Urea Cycle Disorder’) is a condition that affects how your body breaks down protein, from foods such as meat, eggs and dairy (like milk or cheese), or for example during high-intensity exercise, or when fasting.

All the food you eat gets broken down in our digestive system, and the body gets to benefit from vitamins, carbohydrates, minerals, protein and more. For example, when you eat something with a lot of protein like a sausage, the body breaks it down into something called amino acids. 

ammonia build-up diagram

The amino acids travel around our body via the bloodstream and get delivered to cells where they have lots of important functions.

This process creates waste, which the body disposes of accordingly. When protein gets broken down, your body produces ammonia. In people who don’t have UCD, ammonia is removed from the body through what we call the ‘Urea cycle’. When you have UCD, one of the steps in the urea cycle doesn’t work and your body is not able to remove the ammonia. The ammonia then builds up which can be harmful.

If you have a UCD, you may need to take steps to manage your ammonia levels and symptoms. Finding the right treatment plan can allow you to live your life to the fullest. 


A UCD is what we call a genetic disease, this means it is something you are born with. You inherit different genes from your mother and father. Some carry the information that determines the colour of your hair or eyes, whilst other genes have information which may be related to a genetic disease. UCDs can be passed down in families when a parent passes the defective gene to the child. UCDs can also be the result of a spontaneous genetic mutation, which means it happens regardless of the parents’ genes.