Having blood test in 2 weeks do I need to stop taking B12and B complex before test?

I have Graves , had Rai 7years ago. After bad start managed to get meds right till aug last year dr said Tsh too low so dropped levo,it made me hypo.am fed up with dr and NHS ,so am getting private bloods done,want to know what my t3 is dr says this is irrelevant,also having all the vits etc checked as I take B12and bcomplex do I need to stop these before taking test any advice would be greatly appreciated

13 Replies

  • Raventhorpe,

    You want to see whether you are taking sufficient Levothyroxine and B12 so continue taking them but take them after your blood draw which should be early in the morning when TSH is highest.

  • Thanks clutter have booked NHS appointment for 8.30am and am going to do private one at same time next day .

  • Raventhorpe You would need to be off B12 for 4 months to get an accurate level, when supplementing with it the results will not be accurate. As for any other supplements, just don't take them before your blood draw, take them later.

    You need to do your blood test as early as possible in the morning, no later than 9am is best, fast overnight (water only) and leave off thyroid meds for 24 hours.

  • Hi seaside Susie is it worth me doing the test for B12 then? Sorry if being an idiot as quite new to this as always just let dr do what they want before and ended up really ill

  • Is it a Blue Horizon test. If it's part of the test bundle then carry on with it. It will probably show a high level. Are you supplementing because a previous test didn't show an optimal level? You could do Active B12 which is sometimes mentioned here but I don't know anything about it.

  • Did have it tested in Oct it 563 (191-663) not too bad I think? But having such bad pains in joints bad brain fog and depression that thought it could help to up it a bit

  • Mine was similar when I tested. I used a sublingual methylcobalamin lozenge 1000mcg daily, retest showed about 990 so now I supplement 1000mcg 4 days a week as a maintenance dose. you won't overdose, it gets pee'd out.

    Might be an idea to test Vit D as you have joint pains. Google City Assays, they do a fingerprick blood spot test for £28, or do the blue horizon Thyroid Plus Eleven which includes Vit D.

  • Raventhorpe,

    SeasideSusie is right to say that you need to stop supplementing for 4 months if you want a baseline B12 result but if you want to see whether your B12 dose is sufficient your B12 blood test will be accurate.

  • Yes, I worded it badly, thanks Clutter.

  • Thanks clutter, so glad I found this site

  • When you look at your B12 result do remember that only around 20% of the B12 circulating in the blood is available to be transported to the cells where it is needed. This is due the B12 in the blood being both bound and unbound. The Active B12 Test only measures one - the B12 that is available to be transported to the cells. ( Sorry can never remember if it is the bound or unbound that goes to the cells :-) )

  • Did you see this posting today about biotin. Biotin is in most B complexes


    It would seem a good idea to stop B complex at least 4 days before test, in case it affects the thyroid test result

  • Hi slow dragon had seen post, thanks for info will not take my B vits for 4 days before my blood test, I'm so glad I joined this group as wouldn't have known about this

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