Manal,
I have thal intermedia and I am 55 years old. I didn't know I had it until I was 20. I was sick a lot as a child, and had leg pain, but I was also fairly active. My doctor knew there was something wrong with my blood, but didn't know it was thalassemia. My hemoglobin never went above 9.0, and was much of the time in the 7 range. In my twenties, I started having more trouble and it would drop to 6.5. I finally got diagnosed with thal intermedia. My spleen got really big and was making me very sick, and I had to have it out when I was 43. I also had my gall bladder out before that.
People with thalassemia intermedia can vary a lot in hemoglobin levels and how well they can function - that's what makes treatment difficult. There is a wide range of ways to deal with intermediate hemoglobin levels, from not needing much of anything except folic acid, etc., to needing regular transfusions and chelation therapy. I didn't start regular transfusions until 3 years ago. I wish I would have started them when I was in my twenties, because I was sick all the time and in pain a lot. I managed to finish college and get my M.S. degree, but it was a struggle. (Those of you who have heard this before, sorry for the repeat!)
I didn't have trouble with growth development, except for pain in my legs. I'm on the shorter side, 5'3", but that's not unusual for a female. I started having much more pain when I was in my twenties. People can function on lower hemoglobin levels, especially when the body is used to it and when they are younger, but I think it eventually takes its toll. My body is working on a much more efficeint and healthy level now with transfusions. I don't get sick like I used to, and I have more energy.
Your son's hemoglobin levels are pretty low. Does he get sick very often? It sounds like your doctor is knowledgeable and is trying some things that may help a little. It is good to go to a thalassemia center that specializes in the condition. I would keep track of his growth and look for any changes in facial bones. Transfusions will definitely help, but then you have to start chelation which is difficult for young children.
Good luck and please keep asking questions. We don't always have the answers, but we can at least tell you about our experiences. I wish the best for your son and your family. Jean