How can i have a vitamin d deficiency when i'm often outdoors?

Yoru skin: Needs exposure to sunlight. This said - most people are vit d deficient.

Three steps : There are three important steps of vitamin d metabolism. Sources are food, supplementation and sunlight. Conversion must occur in the liver to get biologically active forms of vit d. Vit d is fat soluble, so small amounts daily are sufficient. See nih article < http://ods.Od.Nih.Gov/factsheets/vitamind-healthprofessional/.