I am on it permanently, (100mg 6 days, 150mg 1 day) started when pregnant with DD and am pretty sure it came down very quickly, blood tests were quite frequent 2 weeks sounds about right. Now I still have checked every 4 months or so - I can normally tell if am taking too much or too little now but took about a year to get to that point. ( I have Hashimotos so thyroid antibodies )