There are simple reasons, and not so simple reasons. Erythrocytes are produced in the bone marrow, and certain cancers inhibit the ability to produce these cells. The answer is not as simple as "probably anemia", or "taking B-12". Chronically low hemoglobin levels mean that the patient needs a thorough workup at a competent teaching hospital to evaluate all possibilities.
hi Broozer 555,
Low hemoglobin can be caused by iron deficiency anemia, bleeding too much during a period, or polyps, hemorroids, or many other things. Have you donated blood a lot? You need to find out why. Have your Iron and Iron percent saturation done, and maybe a B12 too along with a chemistry profile to start. Do you have any other information? If not your doctor should be testing you to find out what is going on. Are you extremely tired or have any other symptoms?
mkh9
Broozer555, I attended a clinic at a hospital as mine got low after child birth and they advised that there are a number of reasons it can happen, but not all reasons are as obvious as mine sometimes it cant be explained why it happens.
Hope this helps you.