ohhhhhh *that's* why he put you on D2. omg. i'm pretty confident there's a typo in there and that the "D3" fraction should have (1,25-hydroxy) after it, not the same as the "D2" fraction above it.
here's the problem i think is going on here. once your body makes D3 in the skin, it has three metabolites in your blood
2. 25 hydroxycholecalciferol (sometimes known as calciDIol)
3. 1,25 dihydroxycholecalciferol (aka calciTRIol)
there's more than that, i am over-simplifying, but that's all we need for this discussion at the moment.
anyway the active metabolite of D3 (1,25-dihydroxycholecalciferol) is tightly regulated. 25-hydroxycholecalciferol or calciDIol is your stockpile for making D3. that's what was really depleted in your feb results. that's my strong suspicion at least.
supplemental vit D2 is not 25-hydroxycholecalciferol. it is ergocalciferol, a plant sourced supplement. supplemental vit D3 is sourced from lamb's wool (or in marketing parlance i've heard 'from the sunny meadows of new zealand').
The case against ergocalciferol (vitamin D2) as a vitamin supplementhttp://www.ajcn.org/content/84/4/694.full
"Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification."
i think we should never refer to 'vitamin' D as '2' or '3' at all. it's pretty easy to be clear about supplemental forms and serum forms. in fact i think i will make some changes to some of my summary posts.
we need to be very clear that what we're dealing with are not vitamins. i tend to think of vit D now, in almost the same way i've come to think of uric acid or glutathione peroxidase etc etc etc. except that it is possible to eat foods containing 25-hydroxyvitamin d3 to add to our stores.
so anyway. you are interested primarily in 25-hydroxyvitamin D3, the one that they're calling 'D2' (even though that's so likely to be confused with ergocalciferol).
if your diet is maxed for zinc, calcium and magnesium content, and your serum zinc status stays up and you're taking lots of natural calm, etc etc, plus time in the sunshine, i think 2000IU per day should be plenty for supplemental D3.
i would think, supplement regardless. your level of 26.7, i'm assuming that the units are ng/mL, is still too low to even prevent osteoporosis. 26.7 converts to 66 nmol/L and you want to aim for more like 60 ng/mL or 150 nmol/L. make sure you get more follow up bloodwork in say, august. to see where you're at.