Hi Andy,
Because the data is limited, I have to make some assumptions in order to calculate your vitamin D parameters, so here it is:
How long was vitamin D taken: 8 months = ca. 240 days
(since half of October till half of June)
The dose: 2 000 iu/daily
Total dose: 384 000 iu
= 240 days * (2 000 iu/daily - 400 iu daily usage)
Increase in vitamin D level in blood: (A) 10- (B) 15 ng/ml
Comment: if your level is 19 ng/ml, it is very likely that it was initially (A) 9- (B) 4 ng/ml.
4 ng/ml is however less likely, because it is extremely low.
IUs needed to raise vitamin D level by 1 ng/ml:
(A): (384 000 iu / 10 ng/ml) = 38 400
(B): (384 000 iu / 15 ng/ml) = 25 600
This means that in order to raise your level to say 49 ng/ml, you need to take:
(A) (49 ng/ml - 19 ng/ml) * 38 400 = 1 152 000 iu
(B) (49 ng/ml - 19 ng/ml) * 25 600 = 768 000 iu
How many days you will have to supplement (at dose of 3000 iu):
(A) 1 152 000 iu / (3000 iu daily - 400 iu daily usage) = 443 days (ca 15 months)
(B) 768 000 iu / (3000 iu daily - 400 iu daily usage) = 295 days (ca 10 months)
This means you will have to deal with unpleasant effects of vitamin D deficiency for another year or longer... Even if we assume that these unpleasant effects start to subside at 30 ng/ml (and it seems very likely that they will although this may be not optimal level), this still means half a year of supplementation.
Maybe it's me, maybe I am impatient, but I wouldn't want to wait for so long. So...
How many days you will have to supplement (at dose of 10000 iu):
(A) 1 152 000 iu / (10 000 iu daily - 400 iu daily usage) = 120 days (ca 4 months)
(B) 768 000 iu / (10 000 iu daily - 400 iu daily usage) = 80 days (ca 2,5 months)
It is still kind of long, but to reach this 30 ng/ml level when symptoms subside it will take 1,5 months on average.
Why do doctors do not usually prescribe such a dose? Because they are afraid that the patient may get hypercalcemia (due to secondary hyperparathyroidism), but this fear is quite unwarranted:
http://www.vitamindcouncil.org/vitaminDToxicity.shtml(green crosses on this page are references to relevant scientific research)
To be on the safe side, calcium level should be tested a few times during therapy, and the doctors do not want remember about that, so this results in lower doses prescribed.
And as it showed recently, magnesium can supress parathyroid hormone, and this allows for using the higher dose.
However I know for a fact that some doctors in the U.S. prescribe this high, or even higher doses.
The calculations above look quite complicated, but they are not.
I calculated quite similar values for myself, however I do not remember the exact number, I only remember that at dose of 10 000 iu (on average) it took me 6 months to get to 42 ng/ml.
These calculations always look similarly, as the absorbtion rates of vitamin D are similar and weight is also not that different among different people - so these calculations above apply to almost anybody ie. they show how very long you have to supplement vitamin D...
One exception to this would be people who get a lot of sunshine, but these people will not get vitamin D deficient in the first place -> if someone thinks that he/she gets a lot of sunshine, and has vitamin D deficiency, this means he/she does not get so much sunshine afterall, it only seems so.
and thinking about finding a magnesium supplement
I forgot to mention magnesium before. I am taking it and I am getting less grumpy as I write, but still...
One more thing about itching - have you checked your vitamin B12 status?
I had vitamin B12 deficiency too - effect of not eating too much meat, I suppose.
OK, that's all for now.
B.