Prep advice for optimum blood results

[SleepingDisco]

Hi, apologies if I'm asking a repeat question but I can't find the info in other posts, unfortunately.

I was diagnosed as under active just over a year ago and I'm due check up blood tests for thyroid function and vitamin levels. I remember reading about an alternative supplement that's safe to take in the week before B12 blood test? I currently take Thorne Basic B but will stop taking for 1 week prior to blood draw (I think this is the right approach?) I feel wiped out after a few days of not having this supplement - what can I take instead, temporarily?

And I take my levo dose at night - before bed. Is a pre 9am, fasting blood test the best time to get all bloods drawn? I switched from AM to PM levo after my last blood test (3/4 mths ago) so haven't had one this way round and wondered if I should still do as early as poss. I usually take my levo at 10.30pm ish.

Thanks lots for any help you can offer x

[TiggerMe Ambassador]

Hi, I'll give this a bump as you have slipped through.... you are right some do swap to separates, the knowledgeable will drop in soon 🤗

RedApple SlowDragon

[SleepingDisco in reply to TiggerMe]

Thank you so much! 😘

[TiggerMe Ambassador in reply to SleepingDisco]

Surprised they’ve not picked up I’ve added a couple of tag ins 😉

[Bearo]

will stop taking for 1 week prior to blood draw (I think this is the right approach?)

Kind of. Lots of people say “a week” to be on the safe side and because it’s easy to remember. But I’ve read on here that three or four days should be enough time to leave off B complex/biotin, which is useful to know if you don’t have an alternative with no biotin in it.

[SleepingDisco in reply to Bearo]

Thanks for taking time to reply. I'm at a bit of a loss so have just stopped taking the B complex as my test is a week today. Fills me with dread as I know I'll feel awful in a few days time! But need the tests results so has to be done! Thanks again

[SeasideSusie Remembering]

SleepingDisco

I wasn't around yesterday to see your post and haven't been here much today either.

I remember reading about an alternative supplement that's safe to take in the week before B12 blood test? I currently take Thorne Basic B but will stop taking for 1 week prior to blood draw (I think this is the right approach?) I feel wiped out after a few days of not having this supplement - what can I take instead, temporarily?

If you normally take a B Complex this needs to be left off for 3-7 days before any blood test due to the biotin it contains giving false results. 3 days should be enough for the small amount in a B Complex, eg 400-500mcg, the 7 days is for the large amount in a stand alone biotin supplement or hair/nail supplement, eg 5mg-10mg.

If you take a B12 supplement you can continue this and the result will show what your dose is achieving. If you want to know how much B12 you are holding on to then you need to be off B12 for about 4 months.

If you find that your folate level plummets in the few days without the B Complex you can take a separate methylfolate supplement on those days.

And I take my levo dose at night - before bed. Is a pre 9am, fasting blood test the best time to get all bloods drawn? I switched from AM to PM levo after my last blood test (3/4 mths ago) so haven't had one this way round and wondered if I should still do as early as poss. I usually take my levo at 10.30pm ish.

This depends on whether or not your GP adjusts dose purely by TSH. If s/he does then you need the highest possible TSH to avoid a reduction in dose or when you are looking for an increase. TSH is highest early morning and lowers throughout the day, see graph below. So the best time to test is 9am.

If your GP uses FT4/FT3 to adjust dose (which s/he should) then it's not crucial to have an early morning test.

For those members who take their thyroid meds at night, we suggest that just for the test they adjust time so that the last dose of Levo is 24 hours before the blood draw.

So let's say you're going for a 9am test on Monday morning then you'd adjust as follows

Saturday night - delay this Levo dose and take it Sunday morning

Sunday night - delay this dose until after your test on Monday morning

Monday night - take your dose as normal that night

If you don't make these time changes and you take your night time dose as normal then do the test at 9am then you'll get a false high FT4 (and probably FT3) result. If you leave longer than 24 hours you will get false low results.

TSH

[SleepingDisco in reply to SeasideSusie]

Thank you so much SeasideSusie - this is so useful - I will adhere to the PM levo transition for the blood test next thursday. Unfortunately, my GP seems to think TSH is everything and has dismissed my request for T4 and T3 to be included on my blood form - even though I managed to get it included for my previous test, 3/4 months ago. I'll persist and ask for them to include it - but such a frustrating battle to have to undertake every time - as so many members on here have also experienced!

Thanks again