What are some underlying causes of vitamin deficiency? I'm d, b-12 deficient and have a high fetrin level.

Different causes. Vitamin d deficiency is mainly due to lack of sunlight (although could also increase skin cancer risk). Vitamin B12 deficiency is more nutritional although it's also associated w/gastric disorders leading to loss of intrinsic factor. High ferritin suggests either infection or lots of iron. Best to check w/your family or whoever ordered these tests. Replacement of B12 & d is inexpensive & easy.