I have Vit D deficiency took them five years to diagnose it and it was only after I heard a radio program listing the symptoms and a light came on,that's it. I was being treated for ME at the Maudsley at the time.My problem is a bit different my body doesn't process it well so I need a higher intake.
The calcium and Vit D (horse) tablets they provide on the NHS are crap the Vit D is too low (I know it's possible to have too much Vit D but those levels are at least twenty times higher than most people take) there is a German brand which has 20,000 iu per capsule but it's off prescription but that only means the doctor needs to know about it and then they can still prescribe it.
The knowledge about Vit D deficency amongst most GP,s is appalling they just don't know about it.For instance most people would benefit from 4,000 iu a day (keeping in mind probably 70% of people in a line above Vancouver,NY and London are probably deficient).
I'd suggest your friend looks at the Vit D council website (yank) and get in touch with them if they have questions.( I'm saying that because of their circumstances and also because it's necessary to take other supplements at that same time to ensure you get the most benefit)