I see that discussion has progressed.

From what I've read, including what I linked to in the initial post in this thread, D3 seems to have a longer life/sticks around longer. Secondly, it's more potent, so you need less.

Now, I think there's little doubt that they both work and studies show they both work. There are people who take D3, I've met a few, including family, whose numbers also don't go up. I think it's all quite a bit more complex.

In the end, if you find something that works for you, and it's natural (ideally), then whether it's D2 or 3, really doesn't matter, I think.

But as you both mention, it's important and interesting to see how long it lasts. Honestly, given it's importance, I wouldn't not take any for 3 months in the dead of winter. If you want to see if D2 works without tainting the results with D3, then take some D2 supplements, no? I will say that I'm curious what your numbers will be like in 3 months and don't think your upswing is due to lab error. That doesn't seem very plausible, but that it's not possible.

As for this:

"I have to ask you: If you are afraid of coming off the D3 for just 3 weeks, doesn't that indicate that it would, in fact, be only a short term fix? Certainly, D3 should last longer than that. If it doesn't, then that would confirm exactly what my doctor stated...that it only increases numbers quick and short term...not long term. I know that D2 is Rx and NOT taken every day/week/month, etc...because it's supposed to last in the body (or cells, maybe, as he stated)."

It's worth emphasizing that I'm only taking 1500-2000 IU per day of D3, so nowhere near the numbers I should be taking, because despite using the cream and getting past the GI issues, I'm still getting insomnia, and last night was the worst. The amount of energy and alertness that I get is too intense for me to take higher doses. Clearly I'm sensitive. Once possibility is that I'm not getting enough magnesium, so starting tonight I'm going to up that and see whether the insomnia goes away. If it does, I'll up the dose of the cream by a 1000 IU or so, maybe up to 5000. Let's see. If the insomnia continues, I'll have to switch to D2, since I can't not sleep with my SFN.