All babies have 3 spots of blood collected a few days after they are born. This blood is tested for signs of several different diseases, including galactosaemia. Once a baby has been found to have a high level of this chemical, further tests will be done. These include measuring the enzyme that is missing in galactosaemia and gene testing. All the cells in a person's body contain many, many sets of instructions on how to make the chemicals which make up our bodies.
Mistakes can happen in the gene for the enzyme which is missing in galactosaemia.
A child with mistakes in both copies of the gene will have galactosaemia. Being a carrier has no effect on a person's health. In order for a person to have galactosaemia, both of their parents must be carriers. If a couple, both of whom are carriers of mistakes in the galactosaemia gene, have a child, there are three things that can happen. There is a one in four chance, every time that they have a child, that the child will have galactosaemia.