SophieBella I don't think your GP knows what he is doing. If he started you on 50mcg then increased it to 100mcg after a week then that shows his ignorance. You should stay on the starting dose for 6-8 weeks then retest, it takes 6 weeks for the full impact of Levo to take place.
The aim of a treated hypo patient generally is for TSH to be 1 or below or wherever it is needed for FT4 and FT3 to be in the upper part of their respective reference ranges.
So if your TSH is 2.5, as you haven't given the reference range I am assuming that you are about half way through the range. You have a fair way to go. You should have an increase of 25mcg then retest after 6-8 weeks and see how you are, then increases/retesting every 6-8 weeks until you feel well.
I do OK on Actavis but not everyone does. Ask for a different brand and see if it suits you better. They all have different fillers so there may be something in the Actavis that doesn't agree with you.
From ThyroidUK's main website > About the Thyroid > Hypothyroidism > Treatment Options:
"According to the BMA's booklet, "Understanding Thyroid Disorders", many people do not feel well unless their levels are at the bottom of the TSH range or below and at the top of the FT4 range or a little above."
That book is available on Amazon for about £4.95.
"Dr Toft states in Pulse Magazine, "The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l.
In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance.
But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l.
This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l)."
Dr Toft is past president of The British Thyroid Association and leading endocrinologist. You can obtain a copy of the article by emailing email@example.com , print it off and highlight question 6 to show your GP if he is unwilling to increase your Levo.