I am writing this on behalf of a friend.
She was diagnosed with borderline underactive thyroid after having M E for 15 years. Was put on 25mcg of Thyroxine and later told to slightly increase it to 37.5 but then her blood pressure went up and her doctor told her to reduce the dose to 25 again. Why do you think her BP went up?
I would ask your friend to get her minerals and vitamins checked - Vitamin B12, folate, vitamin D, and ferritin. Blood pressure can be affected by low nutrients.
Do some research on "vitamin deficiency high blood pressure". Vitamin D deficiency gets lots of mentions. And I found this link too, which seemed interesting :
www4.dr-rath-foundation.org...
It might be that your friend has been ill so long that she won't cope with levo - it seems to be a common problem on this forum. She might need NDT or T3. But getting the minerals and vitamins to optimal levels should help, and certainly won't do any harm.
I agree with the post from humanbean. As your friend has been ill for so long - and quite possibly Hypo all that time - it will take a long time to become well. Her vitamins and minerals are probably rock bottom due to a poorly performing thyroid slowing things down. With GOOD levels of B12 - Ferritin - Folate - VitD - the Levo she has been prescribed will not be well metabolised in the body and may nto be converting into the ACTIVE thyroid hormone T3.
I don't expect they tested her FT3 did they ? There can also be allergies to the fillers in T4 which can cause palpitations. In my case it was due to a need for more T3.
The doctor might have to prescribe liothyronine. At least he should add some T3 to the T4 and if that doesn't work NDT (which I doubt they will prescribe) or T3 only.
No I doubt it. Thanks Shaw
Increase Dose (but not telling GP) 
Increased dose and crazy head
BP and HR on Dose Increase
increased thyroxine dose symptoms?
