When my TSH got down to 3. You have to know and watch your own numbers and get to know when you feel best. I’m best between 2–3. Most endocrinologist like patients between 1–2.
When you first start they will try you on a dose, retest in 6–8 weeks, and then change the dose again if need be. Then they should test you again in 6–8 weeks to see where you are and if you need your dose changed again. Once you are between 1–4 they will either leave the dose the same, or maybe change by one pill one day a week to move you just slightly one direction or the other based on how you feel and other symptoms. In my opinion then you should be tested again in 6–8 weeks. Then you can try every 3–6 months, and if you are very stable every 6 months to a year. They also should check your T3 and T4 free.
Anyway, how you feel has everything to do with where your hormone level is at, and for many people it takes 2–6 months to get it right, and some longer. It partly depends how high your TSH was to begin with, and how aggressive your doctor is with the starting doses.
Some people are not very symptimatic, so they don’t feel much different.
My TSH was very very high when I was diagnosed, around 95, and within a month of medication my heart rate was faster (which was good, it had been too slow) I felt like I could take in more oxygen, my blood pressure went back to normal, and a lot of my spacey feeling went away. But, feeling tired and needing more sleep took 3–4 months, until my TSH went down below 4.