Serum vitamin assay is a blood test that measures whether the concentration of various vitamins in the blood serum is within the normal range. Vitamins are important nutrients in maintaining normal body physiology, and vitamins can only be maintained if their concentrations in the blood are within the normal range. If the concentration of vitamins is too low or too high, some pathological conditions will occur, such as vitamin B12 concentration is too low will lead to pernicious anemia such as megaloblastic anemia. Decreased concentrations of folic acid can also lead to megaloblastic anemia. Decreased concentrations of vitamin A can lead to night blindness. A decrease in vitamin C concentration can lead to scurvy, etc. Therefore, the measurement of serum vitamin concentrations can clarify whether the body’s vitamin concentrations are in the normal range and can be used to guide clinical treatment.