The fat-soluble vitamins are vitamins A, D, E, and K — the vitamins that dissolve in fat rather than water, and travel the body’s lipid pathways. They are absorbed with dietary fat, carried in lipoproteins, and stored — in the liver and adipose tissue — which means deficiency develops slowly but excess accumulates dangerously: vitamins A and D are toxic in overdose in a way the water-soluble vitamins are not. Each has its domain: A for vision and immunity, D for calcium and bone, E as the membranes’ antioxidant, K for blood clotting. Fat malabsorption — in coeliac disease, cystic fibrosis, or biliary obstruction — starves the body of all four together. They are the vitamins that need fat to be eaten, stored like fat, and respected like fat: powerful in range, unforgiving in excess.