July 2016 = tsh 25 >put on 25mg synthroid>tsh been going down steadily>feb 2017 = tsh 5.85>dr increased dose to 38mg>2 months later tsh shot up to 18?

Retest TSH & Free T4: Your scenario is unusual. Are the test results valid? hence a retest is reasonable. Are you taking your medicine as prescribed? If the answer to both of the above is yes, then perhaps the potency of the medicine you are taking is suspect.

Thyroidologist: A thyroidologist or endocrinologist is best qualified to evaluate you and regulate your treatment. In some patients synthroid is processed differently and other agents may be prescribed. In other patients generic synthyroid may not give predictable responses of blood levels competed to brand name synthroid. If you aren't seeing a thyroid specialist, discuss this with your pcp.

Thyroid hormone: It may take a little while to get your levels right. If you are taking the medicine correctly which means by itself in the am one hour before breakfast then maybe you still need time to truly adjust to the meds. You will obviously need a higher dose and see what the TSH does after that dose. It takes 4 to 6 weeks to adjust the doses so hang in there. It is the long term trend that matters.