Thyroid UK
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Helping my understand blood test results for Underactive Thyroid

Hi guys,

I have just got back from the doctors. She said my levels are normal and she wants to keep me on 50mg for 3 months and I should see a return of my period.

When I had my first blood tests my Free T4 level was 8.9 and TSH 8.63

Now they are Free T4 14.4 and TSH 1.15

Could someone tell me what the normal levels range are. I have googled but a little confused.

Also I am still feeling awful, I am willing to give it another month on 50mg but if things haven't improved I will go back to the doctor. I am feeling frustrated that my levels are meant to be 'normal' again but I am not feeling 'normal' yet and still no period! It's been 6 months now :(

2 Replies

Unfortunately, we simply CANNOT tell you. The reference ranges vary from one lab to another. You simply have to get them from your GP surgery (along with your results), call the lab, or, if you are lucky, find your lab's laboratory handbook on the internet and look there (be careful, it could be out of date, so always check carefully).



Your GP is keeping you at 50mcg as your TSH is come down to 1.5 which is within the reference range. It is better to ask for a copy/print-out from the surgery as it includes the ranges and request one each time you have a blood test for your own records. You can also post if you have a query.

As you are still feeling unwell, I think she could have raised your dose slightly. It is always better to have gradual increases. The problem with the reference ranges, they don't tell how the patient is feeling and her/his clinical symptoms.Female problems are common in hypothyrodism as well as many other clinical symptoms.

Some of us feel better when our TSH is below 1. Dr Toft of the BTA says:-

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.


If you go to the date April 22, 2007 to read the answer to this question.

The guidelines of the British Thyroid Association state that only levothyroxine is to be prescribed.


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