I do a finger-stick blood draw at home, using a kit from ZRT Labs that costs about $70 with postage. If you go to Dr. Cannell’s site to order it, he gets a cut, which is a good thing because he’s probably doing more than anyone to sort through all the old and the more recent studies and then updating everyone on the results.
Here’s the link to his site page with the test: http://www.zrtlab.com/vitamindcouncil/
There’s also a ton of info on his site, including his specific advice to avoid getting your D3 in the form of cod liver oil. The vitamin A in the form of retinol in cod liver oil will frustrate the uptake of the D3, he says.
Someone said they take 10-20,000 per day. Unless you weigh 300-400 pounds or more, you’d better get tested a few times to make sure you’re not heading into the 150-200 ng/ml level that would constitute overdosing. We don’t excrete the excess vitamin D3, like we do with water soluble vitamins. It just builds up in the fat tissue and can get too high.
And here’s a site that links to several videos of presentations by the current crop of vitamin D3 researchers. If you’re really interested in learning more about the direction the research is taking, the videos will be helpful, though they are long.
http://www.ontrackreading.com/dyslexia-puzzle/vitamin-d3-and-disease
I just wanted to ask where you’ve heard of Vitamin D overdosing? I’ve only heard of it in levels near the millions of IU. From everything I’ve read (from the Vitamin D Council, included) 50,000IU is acceptable each day. I’m not saying that you’re incorrect, because I have heard of problems with calcium for those who take extreme amounts (100k’s IU ranges, but not anything below several 100K), so I am just trying to get more information. I have looked up on the NIH and CDC websites, and not yet found any information on what exactly constitues a vitamin D overdose, but it is something that has been on my mind. I’ll look more into the blood level, I do want to get tested. Thank you again for all of your help.
One quote I found:
“The lack of adverse effects in clinical trials that used intake up to 1250 micrograms [50,000 IU] vitamin D per day and the lack of adverse effects at lower doses inspires a high level of confidence in the data from the strongly designed clinical trials that used 250 micrograms [10,000 IU] vitamin D per day,” said the reviewers.
The researchers also note that for practically all the reported cases of vitamin D toxicity have involved doses that were in excess of those studied in the clinical trials. “Newer clinical trial data are sufficient to show that vitamin D is not toxic at intakes much higher than previously considered unsafe,” said the reviewers.”
-J.N. Hathcock, A. Shao, R. Vieth, R. Heaney. Risk assessment for vitamin D. American Journal of Clinical Nutrition; January 2007, Volume 85, Pages 6-18.
http://www.rejuvenation-science.com/n_vitamin-d-upper-limit.html