Stupid Modern Medicine

So, after upping my dosage of thyroid medicine, I had my TSH level checked last week. My doctor called today, and my level has now moved into slightly hyperthyroid on my current dosage of thyroid replacement medicine. She asked me if I was feeling jittery or if my heart was racing or anything, and I told her I feel the best I've felt since my surgery. Despite that, she decided to lower my dosage, and "we'll see how [I] feel in May and go from there."

Shouldn't there be a better way to determine these things than trial and error?