Under active thyroid was on same dosage for 3 yrs and now all of the sudden the last 5 months the dr cant find right dose?

Hypothyroidism: Hi. As residual endogenous thyroid function falls, dosage adjustments may become necessary. Just don't check too often. Be on a dose for 8 weeks before testing the labs and make sure you're taking your dose everyday. If labs are checked after too short an interval, the body is not yet equilibrated to that dose, and then a change is being made; the labs can jump all over the place. Be patient.