Vitamin D is I think wrongly named as a vitamin. It is, in fact, a hormone and the vitamin D receptors are in every organ of the body.
We tend to think of it as just affecting bones, but it is vital for many processes in the body and recently, of course, the immune system and prevention of respiratory tract infections.
In winter, and really depending on where you live (the
further north you reside), the ability to make vitamin D on your skin decreases. If you are indoors all the time then you will more than likely be deficient.
Therefore, taking vitamin D supplements particularly in the winter is essential.
How do you dose it, you may be asking?
First of all, you may be getting vitamin D on a prescription, if you are taking medicine for bones and osteoporosis. So, check with your pharmacist. Also, watch you are taking D3 -
colecalciferol and not D2.
As far as doses are concerned 400iu or 10mcg is the
recommended dose, but I feel that is too low for adults.
We give babies of 1 day old 400iu in the form of drops, so an adult needs more. 1000/2000iu per day is my recommended amount, but please discuss dosage with a healthcare professional.
Testing levels of vitamin D is generally not needed but you can get a private test if you feel you want to know.