When I was on Naturethroid for the first few weeks, I felt good. I enjoyed the dissipation of brain fog, and I could actually see my knuckles again. Then after those 2 weeks, I began to feel so tired and could not even climb the stairs in my house. I had the doctor order lab work and was shocked to see how low my labs are.I was on Synthroid 175 prior to switching to NT. I did read that Synthroid lingers in the blood for 2 weeks until total dissipation...I'm wondering if this is what caused the sudden decrease in labs and my extreme tiredness.