Welcome Hattie
We all have to start on a low dose and adjust to that before having it stepped up, as a step up of 100mcg or more could be dangerous, if I have understood correctly. You'll need to keep going back. Also, before settling on the right prescription, you will need a blood test to check your thyroid function is within range. Usually the dose arrives at something lower the smaller you are and the lower yor TSH.
We can compare results, but we will need to know lab ranges or the numbers are meaningless. The same blood sample can be sent around the country and come back with a different number, depending on the callibration of the testing equipment in each laboratory (but it should have the same result of coming from someone who is hyper/within range/hypo, despite what is said about 'normal ranges'.)
When I went to get tested, I was feeling terrible, crying lots over the silliest things, couldnt stop putting on weight, feeling extremely cold, etc. and when tested (before treatment) i was 5.8 range: ('mild hypothyroidism, shouldnt need much thyroxine.') I am also 5'1" and weigh about 9st 7.
I was impatient to get more thyroxine and feel well again, so when prescribed 50mcgs again, after 8 weeks, I asked for some extra 25s so I could raise the dose a bit at a time before the next appointment. I gradually raised it to 100, was feeling great, tried 125 and that was far too much. (I had a horrible pain in my chest). This was not wise! I realise now that I could have given myself a heart attack. I was trying to cut down on the number of appointments I would need and see a doctor less and nearly ended up needing emergency care. I hope my cautionary tale helps others understand the risks involved. But also, help give an idea of safety margins. The next blood test I was taking 100mcgs per day and I was hyperthyroid. 0.02, range: So am now taking 50mcgs and awaiting tests. I don't feel like 50 is enough, but want to see what the next blood test result says. (Doctor only wants to prescribe 50mcgs now).