There is absolutely huge controversy about vitamin D. There is a very good recent BMJ debate which is worth digging out.
Here is some of it
The vast majority of people who present with symptoms which might be due to vitamin D deficiency feel absolutely no better after they have received it and do not have altered health outcomes.
There are some exceptions to this, people with recent fractures, osteoporosis and renal problems.
The studies on which recommendations are based are poor. And some things which seem intuitively sensible, like increasing calcium intake with supplements actually increase cardiac risk
So, please, don’t everyone flock to your GP seeking a vitamin D test.