In all forms of thalassemia, there is a varying degree of turnover of red blood cells, as the defective RBCs produced are filtered out by the spleen. This creates an increased demand for certain nutrients, especially folic acid which is necessary for producing RBCs, and this is why I recommend it for all thals.
It is essential to understand why testing is needed. Alpha thal major results in death of the fetus, so alpha minors with two genes deleted in the same cluster always need to have partners tested before having kids, because if the partner is the same, there is a 25% chance of having a major that cannot survive pregnancy and is a danger to the mother's life. Because alpha thal minor is not always easily diagnosed, it may be necessary to do DNA tests to determine if one carries alpha thal.