Medicine & USMLE

Vitamin B3 (Niacin) Biochemistry

  1. Vitamin B1 (Thiamine) Biochemistry
  2. Vitamin B1 (Thiamine) Deficiency
  3. Vitamin B2 (Riboflavin)
  4. Vitamin B3 (Niacin) Biochemistry
  5. Vitamin B3 (Niacin) Deficiency and Excess
  6. Hartnup Disease
  7. Vitamin B5 (Pantothenic Acid)
  8. Vitamin B6 (Pyridoxine)
  9. Vitamin B7 (Biotin)
  10. Vitamin B9 (Folate)
  11. Vitamin B12 (Cobalamin) Biochemistry
  12. Vitamins B9 and B12 Deficiencies
  13. Vitamin A (Retinol) Biochemistry
  14. Vitamin A (Retinol) Deficiency and Excess
  15. Vitamin C (Ascorbic Acid) Biochemistry
  16. Vitamin C (Ascorbic Acid) Deficiency and Excess
  17. Vitamin D Biochemistry
  18. Vitamin D Deficiency and Excess
  19. Vitamin E (Tocopherol/Tocotrienol)
  20. Vitamin K Biochemistry
  21. Vitamin K Deficiency
  22. Zinc
  23. Kwashiorkor and Marasmus


Vitamin B3 (Niacin) is a water-soluble vitamin which serves a key role as a precursor of the coenzymes NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate). Found in foods, niacin is also used pharmacologically as a treatment for lipid disorders, specifically for its ability to raise HDL ("good" cholesterol) and lower VLDL and LDL ("bad" cholesterols). The synthesis of niacin requires a number of factors, including tryptophan, Vitamin B2 (Riboflavin), and Vitamin B6 (Pyridoxine).

Key Points

  • Vitamin B3 (Niacin)
    • Constituent of NAD+ and NADP+ (used in redox reactions)
    • Synthesis requires tryptophan, Vitamin B2 and Vitamin B6
    • Used to treat dyslipidemia
      • Raises HDL levels
      • Lowers VLDL, triglyceride, LDL levels
        • Decreases hepatic production of VLDL, triglyceride release from adipose tissue, and decreases conversion VLDL to LDL

Find Niacin Biochemistry and other Vitamins among Pixorize's visual mnemonics for the USMLE Step 1 and NBME shelf exams.