Vitamin A is a group of biologically active, fat-soluble molecules that includes retinol, retinal, and retinoic acid.

These compounds are derived from the plant precursor molecule beta-carotene, which is converted to vitamin A by intestinal absorptive cells and hepatocytes. Vitamin A is stored in the liver and transported to extrahepatic tissues. It is essential for a number of physiological processes, including vision, organogenesis, tissue differentiation, immune function, reproduction, embryonic development, and maintenance of healthy skin and barrier functions. Vitamin A deficiency can manifest as night blindness, xerophthalmia, follicular hyperkeratosis, increased susceptibility to infection, and anemia. Vitamin A toxicity can occur when excessive levels are consumed and can lead to symptoms such as dizziness, nausea, vomiting, headaches, blurred vision, and vertigo.