Latest labs, advice required please: Hi all... - Thyroid UK

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Latest labs, advice required please


Hi all,

After an increase from 75mcg to 100mcg Levothyroxine, I had my 6 weeks blood test, which I fasted and avoided medication for over 24 hours for. I picked up my latest labs this morning, I'm disappointed to see that the doctor didn't run T3 as she had said she would though so I won't get all the answers I was hoping for but what was tested is as follows:

TSH 0.27 (0.35-3.5)

FT4 13 (8-21)

Using the same ranges, 2 months ago my thyroid levels were:

TSH 1.75

FT4 13

FT3 4.1 (3.8-6)

So, my FT4 hasn't increased at all, despite the increase in dose and decrease of TSH. The doctor wants to call me, presumably due to the below range TSH (which we all know is pretty meaningless) so no doubt wants to lower my medication again! I will point out my FT4 result if they do try to, but I would love some advice on why my FT4 hasn't increased. I wasn't aware of the avoiding medication thing for my first test though, so that's probably the cause, I take my medication at night and had the blood test at 9.30am, so it had probably been a gap of around 10-11 hours. I still have symptoms, mostly brain related but also numb fingers, so would appreciate some advice on where to go next.

The doctor seems to have run some other general blood work and my serum potassium levels have been flagged as being too low (3.4 with a range of 3.6-5). Any ideas what could cause this and whether it is an issue for anything thyroid related?

Thank you all for the wonderful advice from this forum so far!

3 Replies

Also, I forgot to add I asked for a vitamin D test which came back at 74 with adequate levels having a range of 50-120. Is adequate enough or should I increase my supplements? What is the ideal range?

SeasideSusieAdministrator in reply to foxrabbit

foxrabbit The Vit D Council recommends a level of 100-150nmol/L.

Have you had ferritin, folate and B12 tested?

It probably wasn't your GP's fault the FT3 test wasn't carried out. Even when requested it seems to be the lab that decides if it will be done.

If your GP wants to reduce your dose then tell her that with such a low FT4 you're not prepared to.

From ThyroidUK's main website under 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."

The book is written by Dr Anthony Toft, past president of the British Thyroid Association and leading endocrinologist. It is available from pharmacies and 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)."

You can obtain a copy of the article by emailing , print it off and highlight question 6 to show your GP.

Thank you so much for all of your helpful comments, I will definitely get a copy of the article.

My folate and b12 levels are good, my ferritin is low though but you responded to my question on iron supplements with some great suggestions yesterday so I'm working on raising that.

I'll increase my vit d supplements by a bit for a while then to get to a better level.

Thanks again SeasideSusie!

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