Uganda blood transfusion clinical trial begins
14 August 2015 Last updated at 07:46 BST
In sub-Saharan Africa, 60% of blood transfusions go to children – many of whom have severe anaemia.
However, there has never been any large-scale research to find out which of these children really need blood and how much they should be given.
Catherine Byaruhanga went to the Ugandan city of Mbale where a world-first clinical trial is trying to find answers.