Before trying to answer your question, please give us some background information. Have you been diagnosed with Hashimoto's Thyroiditis? What tests were done at time of diagnosis? Have you been tested for the biologically active thyroid hormones, Free T4 and Free T3, which are not the same as Total T4 and Total T3. If so, please post results and reference ranges shown on the lab report. In assessing a thyroid patient's status and treatment symptoms are even more important than test results. So please tell us about any symptoms you have?
Why are you considering self-medication? Are you under a doctor's care?