Thyroid UK
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Blood test timing

Hi everyone

I have a blood test this Wednesday and I have just realised its not until 1.30pm. I know not to take Levo before a blood test in case in skews the results but I also recall reading on here that it should be done as early as possible during the day. Is this right? Will it make a lot of difference to my reading as long as I don't take any Levo before?

Many thanks

2 Replies

Having your blood test done later in the day will produce a lower TSH result than a test done first thing in the morning.

Since many? most? doctors decide your dose on the basis of TSH you may get your dose reduced because of it. Having your test early reduces the risk of this happening, so you should rearrange your test.

Assuming you usually take your levo in the morning, delay taking it until after the blood is taken, then take your levo immediately after.

If you normally take your levo at night then miss out your dose the night before the test, then take the missed dose immediately after the blood draw. Then take your evening levo as usual.


Thanks for that. I will rearrange my test as definitely don't want my dose decreased!!


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