Leonard wrote:
Supplementation may help. I do not exclude the possibility that 7 x 3000 IE (daily intake) is better than 25,000 I.E. once per week.
This was suggested as well in one of the above postings..
When we know perfectly well that the human body creates 10,000~20,000iu the moment it's given the chance of full body skin exposure to UVB it amazes me that anyone keeps on promoting the myth that amounts significantly under that level will have any significant impact on 25(OH)D levels?

We can all see what happens in real life situationsAs in practice it takes up to 10,000iu daily to get most of the population above 40ng/ml 100nmol/l we simply have to use that amount of vitamin d daily to achieve sensible results.
We have to use whatever it takes to raise 25(OH)D to effective levels 50~60ng/ml or 125~150nmol/l
Cityassays vitamin D blood spot test do £25 vitamin D tests £30 for international postage.
Suggesting amounts that are ridiculously low compared to what occurs naturally and what actually can be seen to be ineffective in practice is simply perpetuating the current situation.
Is that really what you intend?
Insanity: doing the same thing over and over again and expecting different results. Albert Einstein.