Blood tests results, can they be misleading?

[Katrina70]

I have had a Serum TSH level of around 0.05 for five years but blood test show its an abnormal level but i felt fine, my doctor has now reduced my levothyroxine by 25micrograms, my bloods came back at 0.55 which is normal but i feel rubbish. Is this normal?

[SeasideSusie Remembering]

Katrina70

Your GP is dosing purely by your TSH level which is wrong. Do you have results, with reference ranges, for FT4 and FT3? Those are the actual thyroid hormones, the FT3 being the most important result. If that is in range then you aren't overmedicated.

By reducing your Levo because your TSH had gone below range, your FT4 and FT3 will have risen and now got to a point where you have started to feel unwell.

In your shoes I would want my dose increased back to 100mcg.

Dr Toft, past president of the British Thyroid Association and leading endocrinologist, wrote in Pulse magazine (the magazine for doctors):

"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)."

You can obtain a copy of the article by emailing Dionne at

[e-mail]

print it and highlight question 6 to show your doctor and say you want FT4 and FT3 tested.