TSH test today after taking Lthyroxin

[Meditationconvert]

Hello, I'm 7 weeks pregnant and have Hashimotos so whilst at GP today wanted to ensure this would be monitored well throughout the pregnancy. She decided to do bloods today, not first thing and I had taken my 100microgram dose in the morning.

I know ideally you should have bloods first thing in the morning and not take thyroxin that morning before the test. Can anyone tell me what impact it may have on the results?

I've been working hard with my Endocrinologist for the last 8 months to keep the TSH levels between 1 and 2.

Thanks

[Mama196]

Is it worth asking GP to note this on file and ask lab to comment?

I’ve only just found about doing test before taking thyroxine in AN I had no idea timing made any difference!

[greygoose]

What time was the blood draw? And what time did you take your levo? And, what was tested? Just TSH or FT4 as well?

We say to have your blood draw early in the morning because that's when the TSH is highest. Doctors don't seem to understand that, and think it's ok to do blood draws at any old time. But, if they're not taken at the same time every time, you cannot compare them. Probably why you're having a hard time keeping it between 1 and 2 - although why you would want it that high, beats me. Most hypos need it below 1 to be well.

Taking your levo in the 24 hours before the blood draw will affect the FT4 (not the TSH) and will be a false high - how high depends on when you took your levo. But, very few doctors understand that!

So, your results all depend on that.

[Meditationconvert in reply to greygoose]

It was Endocrinologist who said ideally between 1 and 2 for fertility purposes.

I took the Levo approx 6.50am on empty stomach with no food or drink for an hour. Blood draw was approx 11.20am.

If that helps? As far as I understand only testing for TSH and fT4

[greygoose in reply to Meditationconvert]

OK, so as it was only about 6.5 hours, you're going to have a false high FT4, and as it was late in the morning, your TSH will be low.

It's so stupid this TSH business. Because the TSH itself has no effect on pregnancy. They should be looking at the FT4 more than the TSH, because that's the one that needs to be optimal. It's T4 that passes the blood/placenta barrier, not the TSH. The TSH level just reacts to your FT4/3 levels - but not always. So, it doesn't matter if your TSH is lower than one, as long as your FT4 is good.

But, if they can't make up their minds what time they're going to do blood draws, then they are never going to be able to stabilise the TSH. You can't just do it any old time of day and expect the TSH to be the same. I don't understand why they don't understand that. And TSH drops after eating.

[Meditationconvert in reply to greygoose]

OK thanks what ideally should T4 levels be?

[greygoose in reply to Meditationconvert]

That's a difficult question to answer, but up over mid-range.