Thyroid UK
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How long before blood tests should I stop taking supplements?

I am currently self-supplementing with 1000iu vitamin D and 1000mcg vitamin B12 daily, alongside a daily vitamin B complex from Boots. If I have my bloods tested again to see if there's any difference to my levels, should I stop taking my supplements prior to testing again and, if so, how long before? Or should I keep taking them all the way to the test?

Many thanks


3 Replies

If you want to know how well the supplements are doing, I would just continue to your test.

Someone who has already done this will also respond.


I don't take supplements, food or drink (other than water) prior to the test in the morning.


When I had my Vit D tested first time I had a long discussion about how long it would take to clear my system and how far in advance I should stop taking my supplement, in the end the person I ordered it from said to carry on taking my supplement and see what the results were. As it was even having supplemented and come back from three weeks in the south of France I was nowhere near the upper limit.

Same with B12, I was tested before I started to supplement, I was just inside the lower limit of the range and my endo was quite happy with that but I have a family history of PA so I bought myself some Jarrows Methylcobalamin and supplemented. I am higher in the range now but even supplementing every day hadn't pushed me over the top of the range when I was tested again although I was at the upper end that time. So if I were you I would just carry on taking them, as the Vit D lady said, if my Vit D was too high I could cut back.


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