Vitamin D is used by the body to process calcium for the bones.
It's naturally occurring when you're in the sunlight.

I strongly suggest that you take a walk after you eat right before sunset.

Make sure that you eat calcium containing products (milk, cheese) as well as items from all the food groups (vegetables, meat, dairy).

If you are lactose intolerant, try taking calcium supplements.
It's best if u allow your body to produce vitamin D naturally instead of taking medication.