Welcome to this site where you will find the best support from people who are experiencing the same symptoms. I have been on 50mcg for the last two years and from recollection noticed a change after a few weeks. My symptons included extreme fatigue, depression because of my inability to get anything done exercise and gardening, which I love and household chores, which I don't. My illness went undetected for many years and I had numerous other symptoms (heart palpitations, anxiety, panic attacks, very dry skin, enlarged tongue, allergies, hair loss, dry gritty eyes, intolerance of bright light, dizziness low blood sugar etc etc all hypothyroid lovelies
I just had a routine six monthly blood test that showed my TSH had risen to 6.5 (normal range 0.5-5.5) and increased by doctor to 25mcg to 75. I have noticed my energy levels rising again and that was after three weeks. Hope this info helps.
Ask for an iron test and Vit D3 as I was deficient in both and intolerant of dairy, gluten and salycylates as are many thyroid sufferers. A good way of gleaning information is to look at the previous blogs and questions on here and there is a search button too.
Good luck and stay with this site if you can as it's invaluable.