Ok so I am suffering from underactive thyroid, I had a blood test and the doctor increased my dose of levothyroxine stating that my levels are normal but would like to get them within optimal range??? What is normal range and what is optimal range I'm confused. I also wanted to know what she ment by there's two things they check when they check my thyroid the levels from the brain to the gland and the levels from the gland to the rest of the body. I might be stupid but I'm really confused. My levels from the gland to the rest of the body have always been normal just the levels from the brain to the gland have not been. Does someone know anything which might clear my confusion. Please help!