TSH blood test

[jojojowilts43]

Hi, I have my blood test today at 12. But I didn't take my levothyroxine yesterday.. and usually take it now . So not taken it since Tuesday. Does it affect the test if it's taken prior to bloods?

[bluebug]

Do not take any medication until after the test.

Next time get your blood test first thing in the morning as that is when TSH levels are highest. If they can't give you an appointment around 9am on a particular date, then find another date where they can.

[LtAngua52]

I hope you haven't eaten either.

[humanbean]

Take a look at the graphs on page 2 of this research paper :

press.endocrine.org/doi/pdf...

You can see how the TSH varies over a 24 hour period. To reduce the risk of getting your levo dose reduced you should have your blood tested as early in the morning as possible because this will get you the highest TSH possible.

So, getting the test done early maximises your TSH.

And not taking your levo for 24 hours reduces your Free T4.

If you were to take your levo then have a blood test within a few hours of it then your Free T4 might be very high. If you don't want your levo dose to be reduced then this kind of result needs to be avoided.

[jojojowilts43 in reply to humanbean]

Hi, I cancelled today test for next week instead but earliest appointment was for 10.45am. I usually take my levo at 9am so what do I do ???

[humanbean in reply to jojojowilts43]

Is there any way you can get blood taken by phlebotomists at your local hospital? If that is a practical suggestion for you then take along the blood form with the tests your GP requested and get it done there when the phlebotomy department first opens instead? I can do this where I live - obviously it isn't practical or even possible for everyone to do the same.

If 10.45am is the earliest you can get it done, then I suggest taking your levo the day before as normal.

On the day of the test take your levo after the blood is taken. Taking it a couple of hours later than usual won't have any effect on you.

If you can't get the blood taken any earlier than 10.45am then you will obviously have to eat. It would be a good idea to restrict yourself to a light breakfast and only drink water if possible until after the blood is taken.

It's a shame the blood draw can't be earlier, but we have to live in the real world, sadly, and it isn't always possible to get things done the way we want.

[Glynisrose]

YES! Never take meds 24 hours before a blood test. Take it after.