ello ysimm,   Sorry I didn't get back to you right away; however, I was researching your question more thoroughly.   Definitely bring this up to both your son's primary care doctor and his psychiatrist or the other professional who is prescribing the Clozaril.  These doctors should be in contact with each other or at least each should be aware of the other's treatment of your son and his lab test results, and symptoms and medications prescribed should be exchanged between the doctors.   I have Googled "thalassemia Clozaril causes" and come up without results in the first 10 Web sites listed.   But you should log on to medlineplus.gov for info on Thalassemia, which is also called Cooley's anemia:   http://www.nlm.nih.gov/medlineplus/thalassemia.html   People of Mediterranean backgrounds are often at risk for certain types of anemia, including Cooley's.   Put your mind at ease by asking the psychiatrist, and by asking the primary care doctor, too, if the primary care person is not aware your son takes Clozaril (though I suspect the medical doctor does know).   I hope I have at least given you some introductory points to consider.   I wish you the best of everything with your son's health.   Chris