| Vitamin | Primary function | Deficiency |
|---|---|---|
| Thiamine (B1) | Decarboxylation of α-keto acids (carbohydrate metabolism) | - Beriberi (peripheral neuropathy, heart failure) - Wernicke-Korsakoff syndrome |
| Riboflavin (B2) | Mitochondrial redox reactions (FMN, FAD) | Cheilosis, stomatitis, glossitis Normocytic anemia |
| Niacin (B3) | Redox reactions (NAD/NADP) | Pellagra (dermatitis, dementia, diarrhea) |
| Pantothenic acid (B5) | Acetylation reactions (CoA) | Distal paresthesia (rare) |
| Pyridoxine (B6) | Transamination of amino acids (amino acid synthesis) | Peripheral neuropathy Cheilosis, stomatitis, glossitis |
| Biotin (B7) | Carboxylase reactions (CO2 carrier) | Dermatitis, conjunctivitis, alopecia, neurologic changes |
| Folate (B9) | Hydroxymethyl/formyl carrier (purine & thymine synthesis) | Megaloblastic anemia Neural tube defects (fetus) |
| Cobalamin (B12) | Isomerase & methyltransferase cofactor (DNA & methionine synthesis) | Megaloblastic anemia Neurologic deficits |
| Ascorbic acid (C) | Hydroxylation of proline & lysine (collagen synthesis) | Scurvy (perifollicular hemorrhage, gingivitis, muscle pain) |