Common causes of vitamin<unk>  deficiency include insufficient dietary intake, as well as diseases and iatrogenic procedures causing problems in absorption. It is common in individuals adhering to vegetarian or vegan diets without external supplementation, due to primary sources including animal products such as meat, eggs, and dairy.
Vitamin B12 deficiency causes
Folate deficiency causes
Iron deficiency anemia causes
Lead poisoning causes
Vitamin D deficiency causes
Lymphocytopenia causes
Hypocalcemia causes
Meningitis causes