Medical Pulse Introduction In recent years, there has been a growing interest in the importance of vitamin D. The importance of vitamin D has been emphasized in a number of studies. The key points of knowledge on vitamin D deficiency are summarized in conjunction with relevant guidelines, with a view to bringing clinical help. Definition of Vitamin D Deficiency Regarding the critical value of vitamin D related to bone health, it is recommended that the Chinese population refer to the following points: ① serum 25(OH)D <30nmol/L, vitamin D deficiency; ② serum 25(OH)D between 30~49.9nmol/L, vitamin D insufficiency in some populations; ③ serum 25(OH)D ≥50nmol/L, almost all populations Vitamin D is sufficient. In clinical practice, physicians may recommend that an individual's vitamin D reach an "appropriate" status, and serum 25(OH)D may need to be 50-75 nmol/L or higher. Effects of Vitamin D on Bone Health Assessment of Vitamin D Status Measurement of 25(OH)D is a good indicator of the body's reserves of vitamin D from both sunlight and dietary sources.The following factors need to be taken into account when measuring 25(OH)D: plasma vitamin D-binding protein and vitamin D-binding protein concentration. The primary method for assessing 25(OH)D is immunoassay, along with high-performance liquid chromatography fluorescence and tandem mass spectrometry. Vitamin D Deficiency Screening Population Patients with bone disease that may improve with vitamin D therapy; patients with bone disease that requires correction of vitamin D deficiency prior to specific treatment; patients with musculoskeletal symptoms due to vitamin D deficiency. Routine vitamin D testing may not be necessary in patients with osteoporosis or fragility fractures who may be treated with both vitamin D supplementation and oral antiresorptive medications. Although vitamin D deficiency is very common, universal screening is not recommended for asymptomatic healthy individuals. Treatment Population 1. Treatment is recommended for serum 25(OH)D <30 nmol/L; 2. Treatment is recommended for serum 25(OH)D between 30 and 49.9 nmol/L with the following risk factors: fragility fracture, history of osteoporosis, or high risk of fracture; application of antiresorptive medications to treat bone disease; symptoms suspected to be the result of vitamin D deficiency; and risk factors for developing vitamin D deficiency. Associated risk factors such as inadequate sun exposure, dark skin; elevated parathyroid glands; use of antiepileptic drugs or oral glucocorticoids; malabsorption-related conditions; 3. Serum 25(OH)D ≥ 50 nmol/L indicates that vitamin D is in the safe range, and maintenance of adequate vitamin D through sun exposure and diet is recommended. Reasonable treatment Individuals who have minimal sun exposure should receive adequate amounts of vitamin D from foods and additives. The recommended intake of vitamin D for people older than 65 years is 600 IU/day; higher doses may be needed for people at high risk for vitamin D deficiency.