• Vitamin K
• Vitamin A
• Vitamin E
• Vitamin B1 (Thiamine)
• Carnitine deficiency

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Vitamins are small organic molecules that are not made in the body (or are made at such low rates that supplementation is necessary), and so must be supplied through the diet. They are generally needed in much smaller quantities than are essential fatty acids or essential amino acids. Vitamins can be conveniently divided into two classes, based on their solubility in lipid vs. water. The fat-soluble vitamins include vitamins A, D, E, and K. The water-soluble vitamins include vitamins B1 (thiamine), B2 (riboflavin), niacin, pyridoxine (vitamin B6), pantothenic acid, biotin, folic acid, cobalamin (vitamin B12), and ascorbic acid (vitamin C). Vitamins in the diet may need to be chemically modified by specific reactions in the body before they become active in metabolism. For example, pyridoxine must be converted to pyridoxal phosphate before it becomes metabolically active.

Vitamins often serve as cofactors for different enzymes, aiding in catalysis of metabolic reactions. A deficiency in dietary intake of one or another vitamin can result in disease, due to lack of enzymic activity of the enzyme(s) for which the vitamin or its activated counterpart is a cofactor.