Thyroid UK
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Could someone interpret these readings for me?

My daughter was prescribed Levothyroxine in October (50 mg) raised to 75mg when she went back in January. More blood tests follow this month but as this is new to us I don't understand the readings which were as follows:

Oct 2012: Serum TSH Level 5.9mu/L 0.27 - 4.20mu/L

Serum Free T4 level 14.0pmol/L 13.60 - 23.20pmol/L

Any information gratefully received!

6 Replies

Hi and welcome :)

Your daughter needs another increase in her thyroxine by the look of these tests. Her TSH (thyroid stimulating hormone) is still quite high which means that her body is sending for her thyroid to make more hormones (including thyroxine) because it doesn't have enough. This test should only be used as a guide and symptoms should really be taken into account when finding the right dose. Most people feel best when their dose of thyroxine reduces their TSH to below 1 (or even suppress it in some cases).

The second test, Serum Free T4 level, is the amount of thyroxine in her blood. This is currently right near the bottom of the range, indicating that she needs another increase in her thyroxine dose. Most people who take thyroxine find that they feel best when their T4 is near or at the top of the range.

How old is your daughter? If she is a child, the ranges are different than for adults and it is important that the correct ranges are used.

It does look like she needs a further increase in her dose of thyroxine.

I hope that helps without confusing the issue too much.

Carolyn x


I meant to say that, if your daughter still doesn't feel right when she appears to be on the optimum dose (TSH below 1, T4 at top of range) please come back to us. There are other things to look at that can affect how well the body uses thyroxine and it may be that these need to be looked at. Low stored iron or vitamin B12 are two issues that can prevent someone from feeling totally better on thyroxine.

And she should make sure she takes her thyroxine away from any food or drink other than water. Some people do better taking it at night rather than in the morning.

Carolyn x


Many thanks for such a quick response. Much appreciated. x


This is a link which is sef-explanatory. Some GP's keep the TSH (thyroid stimulating hormone) around the normal range, but we should aim to have the TSH 1 or below.


rosa, this is a wonderful website that answers almost any question reliably.


Thank you - really appreciate it.


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