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Ways to measure D3


Hi all, 

I have a question on D3 lab tests.

I had my vit D3 checked for two consecutive trimesters, and I'm confused on how to correlate the results.

I had a test in November, where I was tested for 25(OH) vitamin D3. The normal range indicated by my lab is between 20-100 ng/ml. My count was 33.

Then I had a test in February, but this time I was tested for 1.25(OH)2 vitamin D3. The normal range is indicated as 18-65 pg/ml. My count was 40.9.


How can I correlate the results? Is 40.9 good enough?



Btw, regarding why 1.25(OH)2 was ordered instead of 25(OH), I just think it was just a mistake of my doctor's secretary.

See Link below:

"Lab Best Practice: Although IoM recommendations using 25-OH vitamin D are clear, the inappropriate ordering of 1,25 dihydroxyvitamin D is quite common.1,2 The root causes for inappropriate 1,25 dihydroxyvitamin D ordering include: (a) clinicians not understanding the biological role of 25-OH versus 1,25 dihydroxyvitamin D, or (b) 1,25 dihydroxyvitamin D showing up as the “first” orderable test on electronic medical record (EMR) systems. At UC Davis Medical Center, the EMR list for vitamin D has been modified to show 25-OH vitamin D first, rather than 1,25 dihydroxyvitamin D to encourage proper utilization. All 1,25 dihydroxyvitamin D’s are also reviewed for appropriateness. In brief, while 1,25 dihydroxyvitamin D is the most potent vitamin D metabolite, 25-OH vitamin D levels more accurately reflect vitamin D status since it is not influenced by PTH and other hormones. In unique cases such as renal disease, 1,25 dihydroxyvitamin D levels may be used to better determine vitamin D status."

So to answer your question, you had two different tests which are not directly comparable. The 1.25 test was a mistake. You need to re-test with 25(OH) so you can compare.

Hi Scuba,

Thanks, I had found this reference myself, that's why I thought I would ask. 

I suspected that it was a mistake, because this almost happened the previous time as well (the secretary prepares the lab orders), and at last minute my doctor corrected her to change it to 25(OH)...

Thanks anyway for the info!



Just had mine checked at MD Anderson with blood work .  I was too high and plan on cutting back another 1-2 IU.  Tested at 107.  I think it could be that I took the pill a few hours before the test.  I take a 5,000 ui then dinner time 3,000 ui.  I now work inside so I need to find my balance.  I will have to inquired the type of test after reading this string.

I had that happen once where I tested at 100 (transition from winter to spring). What I did was stop taking vitamin D3 completely for 3 weeks and re-test.

It takes about 60 days for 1/2 of vitamin D to get used up on average. And sure enough, I dropped to around 60 after that time. I then resumed my summer program of 5,000 per day as well as not take any on days I was out in the sun (scuba diving!). Be sure they are testing 25(OH) version of D.

ok I will go to 5,000 ui per day.  I am a bit afraid to stop completely since working at a airport now I come into contact with many people.  I miss the solitude of my old career.  Never around many people but I do think the chemicals i worked in may be a factor in my dx.  Any thoughts on the 5k amount Scuba?



Hi Steff,

Stopping is o.k. - it takes months for vitamin D to drop only by half - and it takes months to build. Make sure you are taking vitamin K2 every day as well (200 mcg). K2 uses D as it moves calcium around. Hard to overdo vitamin D when there is plenty of K2 around. Good for your bones too!

 Thanks and yes I use k2....Full Spectrum puts out a k2 with mk4 and 7.  I was taking k2 twice a day same as the d3.