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Vitamin B12 deficiency anemia
Vitamin B12 deficiency anemia is a megaloblastic anemia caused by insufficient cobalamin, arising from poor diet or failed gastric or ileal absorption, and is the leading cause of megaloblastic anemia worldwide.
Vitamin B12-binding protein
Vitamin B12-binding proteins: intrinsic factor, transcobalamin, and haptocorrin, the three mammalian carriers that bind cobalamin with femtomolar affinity, mediate its gastric absorption, blood transport, and cellular uptake.
Vitamin B12-responsive methylmalonic acidemia
Vitamin B12-responsive methylmalonic acidemia is an inherited metabolic disorder in which methylmalonic acid builds up because of defective vitamin B12 metabolism, causing ketoacidotic comas in infancy that improve with vitamin B12 treatment.
Vitamin B12-unresponsive methylmalonic acidemia
Vitamin B12-unresponsive methylmalonic acidemia (mut0, mut-) is an autosomal recessive MUT-gene disorder of methylmalonyl-CoA mutase causing neonatal ketoacidosis, hyperammonemia, renal failure, and metabolic stroke that cobalamin therapy does not improve.
Vitamin B2 deficiency
Vitamin B2 deficiency (ariboflavinosis) is riboflavin insufficiency causing angular stomatitis, cheilosis, and anemia; diagnosed by EGRAC >1.4, treated with oral riboflavin, rare in the US but common in some surveyed populations.
Vitamin B3 deficiency
Vitamin B3 deficiency (niacin deficiency, pellagra) is a systemic disease from lack of niacin or tryptophan, causing dermatitis, diarrhea, dementia, and death if untreated; treated with nicotinamide.
Vitamin B6
Vitamin B6 (pyridoxine and related vitamers) is a water-soluble vitamin and PLP coenzyme in over 100 enzyme reactions; US RDA 1.3 mg/day, EFSA 2023 upper limit 12 mg/day, high doses cause neuropathy.
Vitamin B6 deficiency
Vitamin B6 deficiency (pyridoxine deficiency, ICD-11 5B5D): uncommon nutritional disorder usually occurring with other B-vitamin deficiencies; causes microcytic anemia, dermatitis, glossitis, seizures, and confusion, treated with oral pyridoxine.
Vitamin C
Vitamin C (L-ascorbic acid, C6H8O6) is an essential water-soluble vitamin humans cannot synthesize; needed for collagen, carnitine, and neurotransmitter synthesis, antioxidant and iron absorption; deficiency causes scurvy; RDA 90/75 mg; isolated by Szent-Györgyi.
Vitamin C deficiency
Vitamin C deficiency (ascorbic acid deficiency) causes scurvy, a collagen-related syndrome of bleeding gums, petechiae, and bone pain after weeks of low intake; treated with 500 mg/day vitamin C, rare but seen in restricted diets and refugees.
Vitamin C megadosage
Vitamin C megadosage, or megadosing, is taking gram-or-more doses of vitamin C on the belief it prevents colds and cancer, a practice championed by Linus Pauling in 1970.
Vitamin D
Vitamin D (calciferol): fat-soluble prohormone made in skin by UVB, activated via liver and kidney hydroxylations; forms D2 and D3; prevents rickets and osteomalacia; RDAs 600–800 IU.
Vitamin D and neurology
Vitamin D and neurology: the neurosteroid role of vitamin D (cholecalciferol, calcitriol) in the brain, its links to dementia, MS, Parkinson's disease, and depression, and why trials show limited benefit beyond correcting deficiency.
Vitamin D deficiency
Vitamin D deficiency, also called hypovitaminosis D, is low serum 25(OH)D causing rickets in children and osteomalacia in adults. Distinguished by 25(OH)D thresholds (<30 nmol/L deficient), UVB/dietary causes, and USPSTF findings against routine screening.
Vitamin D deficiency osteomalacia
Vitamin D deficiency osteomalacia (ICD-11 5B57.1), adult soft-bone disease from impaired osteoid mineralization due to severe vitamin D deficiency; bone pain, myopathy, Looser zones, low 25(OH)D, treated with vitamin D and calcium.
Vitamin D deficiency rickets
Vitamin D deficiency rickets (nutritional rickets, ICD-11 5B57.0) is defective growth-plate mineralization in children caused by vitamin D and/or calcium deficiency, treated with vitamin D repletion and prevented by 400 IU daily infant supplementation.
Vitamin D toxicity
Vitamin D toxicity (hypervitaminosis D) is hypercalcemia from excessive supplement intake, with 25(OH)D typically above 150 ng/mL; caused by supplement overuse, manufacturing errors, and fortification mistakes.
Vitamin deficiency
Vitamin deficiency: inadequate intake of one of the 13 essential vitamins (A, C, D, E, K, B vitamins), causing diseases such as scurvy, beriberi, pellagra, rickets, and pernicious anemia; prevented by diverse diets, fortification, and targeted supplementation.
Vitamin E
Vitamin E is a fat-soluble nutrient of eight related compounds, only one of which, alpha-tocopherol, meets human requirements; it is found in nuts, seeds, and vegetable oils.
Vitamin E deficiency
Vitamin E deficiency, also called AVED when inherited, is rare α-tocopherol shortage from fat malabsorption, α-TTP genetic defects, or malnutrition, causing ataxia, neuropathy, anemia, and retinopathy, treated with high-dose oral vitamin E.
Vitamin excesses
Vitamin excesses (ICD-11 5B90) are disorders from oversupply of vitamins, chiefly fat-soluble A and D plus B6; includes hypervitaminosis A, hypercarotenaemia, hypervitaminosis D, and megavitamin-B6 syndrome, usually from supplements.
Vitamin K
Vitamin K (phylloquinone K1, menaquinones K2 incl. MK-4 and MK-7): fat-soluble cofactor of GGCX γ-carboxylation enabling clotting factors II, VII, IX, X; needs, warfarin interaction, newborn prophylaxis, bone and heart evidence.
Vitamin K antagonist embryofetopathy
Vitamin K antagonist embryofetopathy, also called warfarin embryopathy or fetal warfarin syndrome (ICD-10 Q86.2), is a pattern of fetal defects from maternal warfarin use in pregnancy: nasal hypoplasia, stippled epiphyses, CNS and ocular abnormalities.
Vitamin K deficiency
Vitamin K deficiency (VKD) is a common acquired coagulopathy impairing clotting factors II, VII, IX, and X. Also called vitamin K deficiency bleeding (VKDB) in newborns, it is prevented by 1 mg intramuscular vitamin K prophylaxis at birth.
Vitamin K2
Vitamin K2 (menaquinone, MK-4 to MK-13) is the bacterial-origin family of vitamin K found in fermented foods like natto (MK-7) and animal foods (MK-4), with longer circulation than K1, roles in bone and vascular protein activation, and 45 mg MK-4 osteoporosis treatment in Japan.
Vitantonio Lovallo
Vitantonio Lovallo ("Zitòn", 1914–2026), Italian supercentenarian from Avigliano, Basilicata; WWII POW; oldest living man in Italy from 2024 and in Europe from May 2026; died at 112 years, 171 days.
Vitebsk State Medical University
Vitebsk State Medical University (Віцебскі дзяржаўны медыцынскі універсітэт), a public medical university in Vitebsk, Belarus, founded November 1, 1934; first Belarusian medical university (1998), 6-year Vrach degree, Russian and English instruction.
Vitelline veins
Vitelline veins, or omphalomesenteric veins, are paired embryonic veins from the yolk sac to the sinus venosus; their selective involution forms the portal vein, splenic and mesenteric veins, and part of the inferior vena cava.
Vitiligo
Vitiligo, an autoimmune skin disease destroying melanocytes and causing white patches, affects about 1% of people worldwide; treatments include NB-UVB phototherapy and ruxolitinib cream, the first FDA-approved repigmentation drug (2022).
Vitrectomy
Vitrectomy is eye surgery removing vitreous gel to treat retinal diseases, such as detachment and macular holes; the procedure replaces the gel with saline, gas, or oil.