Hello Sarah and welcome to the site
Concerning your question,you are right thalassemia major is diagnoised after few months from birth.
But there are two other classifications of thalassemia which are thalassemia intermedia and thalassemia minor. Intermedia is when you have two muted genes but still your body can produce some good hb and the hb in intermedia ranges between 6 to 10 and it can be diagnoised at a later stage in life.
While thal minor is having one muted gene, meaning you are a carrier of the disease, in other words you can pass the
disease to your children IF your partner is a carrier too (25% chance ). Usually thal minor cases ranges from having anemia with some symptoms to not having any symptoms at all.
But first you should eliminate the possibility of having iron deficiency anemia ( different kind of anemia that differes from thalassemia) which is determined by having a full iron study to check your levels.
Blood Electrophoresis test, is the name of the test that determines whether you are a carrier of thalassemia or not.
Sarah, how much is your HB level??
You can also read more about thal in these links
http://www.thalassemiapatientsandfriends.com/index.php?topic=1571.0http://www.thalassemiapatientsandfriends.com/index.php?topic=1575.0Please feel free to ask what ever you want
manal