I tried the natural thyroid extracts before I tried actual T4 and T3 therapy. It should work pretty much instantly. What I felt from the natural thyroid extract supplements was rapid heartbeat and sweating, which is akin to taking too much thyroid hormone. I would rather you get prescription T4 and go from there since there is no way of quantifying the amount of T4 or T3 in the over the counter thyroid extract supplements. For example when I take T4...if I take 50 micrograms my hands and feet are warmer, I have energy and can think clearly, but if I go to 75 micrograms I am sweating profusely and completely intolerant of heat. I will have to lower the thermostat to 60 degrees F and still be sweating. So thyroid meds definitely require an exact dosing in my opinion. On top of that the extracts are similar to armor thyroid in that they contain T3 + T4, so that makes it even harder to dose because the T3 hits instantly. Some doctors think that you can take as much T4 as you want and not all of it will convert but that is certainly not my experience. Some people can't convert adequate amounts of T4 to T3 so they do better on combination T4+T3 therapy. T3 is too short acting for me and I don't seem to have that problem. I like T4 because I take it once in the morning on an empty stomach and am good the rest of the day. I had horrible results on those thyroid extract supplements and they probably do more harm than good since hyperthyroidism can produce the same fatigue of hypothyroidism. If the dose is right it should work instantly at least for some of the symptoms of deficiency. The brain can only use T4 and not T3 to produce energy so I think solo T3 therapy is also a bad idea. I would get on T4 if possible and then test your T4 and T3 levels and if you still have low T3 after increasing the T4 dose then add T3 to the T4 under the supervision of a doc. Thyroid replacement is one thing that is really hard to screw up as a doctor since there are so many diagnostic parameters - the hardest part in your case sounds like just finding a new doctor to treat you. My thyroid was completely normal on labs most of my life but most of my life I had chronically cold hands and feet that would have benefited immensely. My doctor is of the opinion that everyone needs thyroid hormone in my area especially since they removed iodine from a lot of salt.