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Thyroid UK
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What do all the TSH, t3 and T4 levels mean?

I was diagnosed as hypothyroid about 6 weeks ago and have been on a dose of 100mcg. I go back for more tests to check the levels in a couple of weeks, but don't know what any of it means. I didn't know to ask for the results when I was first diagnosed and so don't know what they were originally. I know that TSH is thyroid stimulating hormone, but don't know what T3 and T4 means and what the right levels should be. Can anyone explain what they all mean and what I should be looking for?

Thank you

7 Replies

I suggest you have a read of the main Thyroid UK site - maybe start here:


Also, you could go to your surgery and ask for previous results. See here:



1 like

I quite agree with Rod. You can ask for your results and should certainly do so. I find it quite appalling however that your doctor gave you this diagnosis and replacement thyroid hormones without explaining anything to you. Jane x


I didn't think about it at the time, but yes, there was a lack of explanation. It was suggested that I look hypothyroidism up online, which is how I found this site. I don't understand the numbers and would like to know what are normal levels of TSH, T3 and T4, so that I can tell just how far out I was/am.


Each laboratory has its own reference ranges. You simply cannot use general "normal" levels but have to consider the results against the reference ranges that should accompany results. The ranges tend to be broadly similar but with sufficient variation that it is very possible to make a mistake if you do not do so.

Please ask your surgery for your results - and make sure they include the reference ranges.

Lack of explanation is so common we pretty much expect it. Not good, not at all good.

By the way, if you click on Reply to this your reply gets indented below the response you are replying to - and the person gets an alert that you have responded. Don't worry - everyone misses that to begin with. :-)



you can phone up the dr's and they should give you the TSH and T4 results over the phone, mine just did, although they didn't test t3 for me, will ask them to next time I go. i've also just been diagnosed hypo, after new surgery health check and blood tests. Dr also didn't say very much, but i had already looked things up online as they repeated my thyroid tests, i think she could see that i was fairly well informed, but she didn't seem keen to discuss it.


Hi PJ - have a look at the main website and also the support group here.

It is strange that on one hand, we are told that most of what's on the internet is rubbish, yet doctors say look it up!

Ranges vary per lab - here's mine in Shropshire - just to give you some idea....

TSH - a test of the pituitary signal to the thyroid - range (0.35-5.50) mU/L - high usually means the thyroid is struggling, low is better if HYPOthyroid.

Free T4 (T4 is the storage Thyroid hormone - free means what's available to use) range here (11-23) pmol/L

Free T3 (T3 is the active Thyroid hormone but rarely measured if TSH in range) range here (3.5-6.5) pmol/L

There's a book available at most Chemists called 'understanding Thyroid disorders' by Dr Anthony Toft - this may help explain a few things (also available from Thyroid UK - who created this support group with HU). However, blood ranges are only an indicator - it really depends on how you're feeling J :D


Hi sparring, just a quickie, as I have no thyroid now isn't TSH pointless for me? The only T4 in my system is my levo


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