u can use it longer than 6 weeks...just stay at same dose, or ramp up, BUT be sure to always ramp down for a couple weeks at end...just my opinion and the way i have used it. i usually use it 8-10 weeks, starting w/ 50mcg, increasing every 2 days till i get to 100 or 150mcg, staying there, then ramping down much slower at end until i'm at only 25mcg for last couple days...