Hello, Cannot say in your particular case, but generally, the categories are blood loss or not making blood. Looking at either the age of the red cells (are there young/new ones) or the amount of the iron around would be able to differentiate between these causes. There can also be autoimmune disease or other causes of blood cells being destroyed by the body. This is rare and the level of iron scavenging protein would tell if this is occurring because all the scavenging protein would get used up if there is blood destruction. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Matt Wachsman, Addiction Medicine Specialist