http://www.vitamindcouncil.org/blog/activated-vitamin-d-vs-25ohd-levels-what-should-you-measure/
Unlike 25(OH)D, calcitriol in the blood is an adaptive hormone; it is inversely related to the amount of calcium in the intestine. If there is no calcium in the intestine, calcitriol levels go up to remove calcium from bone making osteoporosis worse. If calcium is present in sufficient quantities in the intestine, that calcium is absorbed and activated vitamin D levels fall.
Calcitriol in the blood, for just one draw in one patient, has little relationship to 25(OH)D levels. In fact, 25(OH)D levels are often low when calcitriol levels are high. The reference range for calcitriol is usually 17–75 ng/L for healthy adults.
A few months ago, I got a letter from a woman who mistakenly had her calcitriol levels measured. Her calcitriol levels were high even though her 25(OH)D levels were low. I recommended that she take extra calcium in her diet and also take a supplement that contained calcium, magnesium, K2, and zinc. I also recommended that she take 5,000 IU/day of vitamin D even though her activated vitamin D levels were high. Below is her follow up letter.
Hi Dr Cannell:
I wanted to keep my promise and follow up with you regarding the high calcitriol that had everyone so concerned.
You instructed me to start taking at least 1000 mg of Calcium/Mg/ZN daily. I also began taking 5,000 IU/day of D3. I have begun drinking milk again and my calcium intake has come closer to 2000 mg daily over the last two months.
- On 10-12-2012 the calcitriol level was 128 ng/L.
- On 11-12-2012 the level was 95.0
- On 21-21-2012 the level was 62.0.