A vitamin is an organic compound and an essential nutrient, or micronutrient, that an organism needs in small amounts. An organic chemical compound (or related set of compounds) is called a vitamin when the organism cannot make the compound itself, (either at all, or in sufficient quantities) and it must be obtained through the diet. Different organisms have different vitamin needs. For example, vitamin C is needed in the diet by humans and other primates, but other animals can synthesize it. Vitamin D is a needed micronutrient when its synthesis, initiated by skin exposure to ultraviolet light, is insufficient due to a lack of adequate skin exposure to sunlight.
Vitamin deficiency anemia can occur if you don’t eat enough folate, vitamin B-12 or vitamin C. Or vitamin deficiency anemia can occur if your body has trouble absorbing or processing these vitamins. Not all anemias are caused by a vitamin deficiency. Other causes include iron deficiency and certain blood diseases.