I had a blood test 3 years ago and I was told I would need to be retested every year. I never spoke to the doctor after that first test but the receptionist told me that there was a problem with my T4 levels (not sure what that means). I had another test last August and have had 2 more in the last couple of days. I managed to speak to my doctor this time and all he said was I have an under active thyroid. He said that the results last August where 5.8 and now this time it is 4.7, what does that mean? And do you know why I have had 2 lots of blood tests done with in a week of each other. I should get the results back before Friday, but if anyone could give me some information, I would really appreciate it, as I don't have a clue.