I believe it was anywhere from a couple weeks or a month maybe. I switched to Armour after that.
I personally wouldn't start with an NDT product like that. I think it will probably just be confusing to figure out what's going on without the ability to be precise. If your temp and pulse are both low and you want to look into thyroid as a tool to get it up, I'd definitely use something like Armor, or Cynomel/Cynoplus.
If you haven't seen this article by Danny, it's very helpful.
There's a lot of good info on this page as well.