Timing Of Blood Test

[Sparklingsunshine]

Hi

I've been asked to book in for repeat bloods by my GP following a Levo dose increase. My last lot were 4 October. I see the advice is between 6-8 weeks. I'm trying to book online now as there is always high demand. Is it better to go for 6 weeks or leave it until 8?

And what's the best time. I know you advise before 9am, but is that well before or close to 9am? Appointments start at 8am in my area. Many thanks.

[greygoose]

Whether you should wait 6 or 8 weeks between starting a new dose and the blood test depends very much on how long you've been taking levo, and how much you're taking. If you've only just started levo on, say, 25 mcg then six weeks would be better. But, if you're taking 150 mcg and have been taking it for years, 8 weeks would probably be better. It's not an exact science.

The earlier you get the blood draw, the higher your TSH. And as doctors only tend to look at the TSH, if you want an increase in dose, the earlier the better. So, if you can get a slot at 8 am, I'd go for it, if I were you. The reason we say before 9 am is because the TSH drops quite sharply at 9.

[Sparklingsunshine in reply to greygoose]

Hi

I've been on Levo since June 2020, started on 50mcg then 75mcg, then 100mcg, then last week GP increased dose again to 125mcg.

Following blood tests in early October. So was unsure whether to retest at 6 or 8 weeks. Thanks.

[greygoose in reply to Sparklingsunshine]

Oh, at this stage in the game, I would wait 8 weeks, if I were you.

[SeasideSusie Remembering]

Sparklingsunshine

When I change dose I have found that I need a minimum of 8 weeks for levels to settle, even if I test at 8 weeks then I can still feel a change by week 10.

As for timing, check out this graph of the daily rhythm of TSH (first graph on page, scroll down a bit):

thyroidpatients.ca/2020/07/...

You will see TSH is highest between midnight and 3am, then it lowers then has a little rise at 9am before it starts to lower again. I always do my tests between 8.45 and 9am at home. My surgery doesn't start blood tests until 9am but as my TSH is always suppressed it really doesn't matter what time I have it done there.

[Purplesash in reply to SeasideSusie]

When I change dose I have found that I need a minimum of 8 weeks for levels to settle, even if I test at 8 weeks then I can still feel a change by week 10.

This is really interesting SeasideSusie, I had blood test taken 8-9 weeks after a drop in Levo from 175mcg to 150mcg and the blood tests showed little change, however not long after that last blood test I started feeling much worse, chronic fatigue etc and suspect that when I have my next blood test, the results will be much different. I have been on a Levo for a very long time, around 26 years or so.

I am booked in for blood test next week with GP and have requested they test my FT3 too, doctor has requested this on blood form but said lab may ignore it and they only do it by request of Endo. Makes me mad that the labs can ignore doctors requests and do as they please. Fingers crossed though I get lucky and they do the test as requested.