Every unit of blood contains about one fifth of a gram of iron, so a thalassaemic person who receives 20 units of blood a year, also receives about 4 grams of iron a year. There is no natural way of getting rid of this iron, so it has to be stored.At first the extra iron is stored in the liver. The liver seems able to store away about 20 grams of iron without much difficulty. Most thalassaemic children are able to store all the iron they receive safely, up to about I I years of age. Your liver may enlarge a little to fit it all in, so it may be a bit easier to feel the liver edge in thalassaemics than in other people. There is no harm in this. However, after about I I years of age, the stores are full, and the iron begins to accumulate in places like the heart...In principle, new patients should start after they have received about 20 units of blood.