Thyroid UK
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Re-testing Vit D - do I need to leave off supplement, if so for how long?

Title pretty much says it all. I'm hypo, currently taking Vit D amongst many other things, have been doing so for months, and want to re-check my levels. I was taking 5000 i.u. for around 3 months at the end of last year, then switched to 1000 i.u. daily this year. My Vit D was quite low back in August '16, pre-supplementation. My result was:66.1 <50 adequate, <220 high so I had a fair bit of room for improvement. I don't get out in the sunshine much or if I do, I cover up.

Should I quit taking the supplement before I do the blood spot test, and if so, for how long beforehand?

4 Replies

Jadzhia You don't need to leave D3 supplements off for any length of time, just don't take it on the morning of the test, maybe the day before as well.

City Assays has a video about the test and I think towards the end it tells you

Recommended level is 100-150nmol/L.


Thanks SeasideSusie, yes they do indeed say just don't take Vit D on the morning of your test, so that's cleared that up. :)


I wouldn't take it 24 hours before the test just to be on the safe side.

I have had one false reading for a vitamin D test but I was on a very high dose.

1 like

Thanks bluebug, will do! :)


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