http://www.medications.com/effect/view/38551 I have been using Eltroxin 0.05mg for 8 days and feeling worse then before. What is the purpose? This medication should be banned. But what alternative is there for under active thyroid? Wed, 10 Jun 2009 13:41:57 -0400 http://www.medications.com/effect/view/38551?item=20499 It takes 4 to 6 weeks for this medication (or any form of levothyroxine) to build up in your system so it takes a while to see the changes. Be patient. http://www.medications.com/effect/view/38551?item=20499