The American College of Endocrinology recently published a clinical practice guideline for the assessment, treatment and prevention of vitamin D deficiency, which further clarifies the specific implementation of effective assessment, dietary supplementation and pharmacological prophylaxis for vitamin D deficiency in high- and low-risk populations of different age groups and disease backgrounds, specifying the uncertainty of the non-blood calcium benefit of vitamin D. The guideline aims to achieve The aim is to optimize the prevention and treatment of vitamin D deficiency. Large Populations at high risk for vitamin D deficiency (e.g., Hispanics, blacks, pregnant women, and obese individuals) should be screened for vitamin D levels, but universal screening of populations is not recommended. A peripheral blood serum 25-hydroxyvitamin D level of less than 20 ng/ml should be diagnosed as vitamin D deficiency. Vitamin D deficiency is common in all age groups, and only small amounts of food contain vitamin D. Vitamin D supplementation should be administered at recommended daily intakes and at tolerable upper limits, and in accordance with age and clinical practice, to prevent cardiovascular disease, death, or to improve quality of life. A reliable method of measuring serum 25-hydroxyvitamin D levels is recommended as an initial laboratory test for those at risk of vitamin D deficiency. Treatment with vitamin D2 or vitamin D3 is recommended for those with vitamin D deficiency, while dietary supplementation is recommended for those at high risk. Key points of the guidelines are as follows: 1. Diagnostic procedures 1) Screening for vitamin D levels is recommended for people at high risk of vitamin D deficiency, but universal screening is not recommended for people without risk factors. (2) It is recommended that serum circulating 25-hydroxyvitamin D levels be measured by a reliable method for those at risk for vitamin D deficiency to evaluate the vitamin D status of the patient’s body. Vitamin D deficiency is defined as 25(OH)D levels below 20 ng/ml. serum 1,25-dihydroxyvitamin D testing is not recommended for the evaluation of vitamin D deficiency and should only be used when monitoring specific conditions such as acquired and inherited disorders of vitamin D and phosphate metabolism. 2. Dietary supplementation of vitamin D is recommended for people at risk for vitamin D deficiency (1) The minimum requirement for vitamin D is 400 IU/d for infants and children 0 to 1 year of age, and at least 600 IU/d for children 1 year and older to maximize bone health. It is unknown whether 400 and 600 IU/d requirements will meet the potential non-skeletal health benefits associated with vitamin D in children 0 to 1 year and 1 to 18 years of age, respectively. However, at least 1000 IU/d vitamin D may be required to keep blood 25(OH)D levels above 30 ng/ml. (2) Adults aged 19 to 50 years require at least 1000 IU/d vitamin D to maximize bone health and muscle function. It is not known if 600 IU/d is sufficient for the potential non-skeletal health benefits associated with vitamin D. However, if blood 25(OH)D levels are consistently above 30 ng/ml, at least 1500 to 2000 IU/d vitamin D may be required. (3) Adults aged 50 to 70 years and adults over 70 years require at least 600 and 800 IU/d vitamin D, respectively. 600 and 800 IU/d are not known to meet the potential non-skeletal health benefits associated with vitamin D. However, if blood 25(OH)D levels are consistently above 30 ng/ml, at least 1500 to 2000 IU/d vitamin D may be required. However, at least 1500 to 2000 IU/d vitamin D supplementation may be required to maintain blood 25(OH)D levels consistently above 30 ng/ml. (4) Pregnant and lactating women require at least 600 IU/d vitamin D and may require 1500 to 2000 IU/d vitamin D to maintain blood 25(OH)D levels consistently above 30 ng/ml. (5) Obese children and adults and children and adults taking anticonvulsants, glucocorticoids, antifungals such as ketoconazole and treated for AIDS require at least two or three times the amount of vitamin D of the same age group to maintain the body’s vitamin D requirements. (6) The upper limit (UL) of the tolerable maintenance dose of vitamin D, i.e., the limit that should not be exceeded except by physician’s recommendation: 1000 IU/d for infants younger than 6 months, 1500 IU/d for infants 6 months to 1 year, at least 2500 IU/d for children 1 to 3 years, 3000 IU/d for children 4 to 8 years, and 4000 IU/d for those older than 8 years. 3. Treatment and prevention strategies ⑴ Vitamin D2 or vitamin D3 is recommended for the treatment and prevention of vitamin D deficiency. (2) It is recommended that infants and children aged 0-1 years with vitamin D deficiency be treated with 2000 IU/d vitamin D2 or vitamin D3, or with 50,000 IU vitamin D2 or vitamin D3 once a week for 6 weeks to bring blood 25(OH)D levels above 30 ng/ml, with maintenance therapy at 400-1000 IU/d. (3) It is recommended that children aged 1-18 years with vitamin D deficiency be treated with 2000 IU/d vitamin D2 or vitamin D3 for at least 6 weeks or with 50,000 IU vitamin D2 or vitamin D3 once weekly for 6 weeks to achieve blood 25(OH)D levels above 30 ng/ml and maintenance therapy at 600-1000 IU/d. (4) It is recommended that all vitamin D-deficient adults be treated with 50,000 IU vitamin D2 or vitamin D3 once a week for 8 weeks or an equivalent dose of 6000 IU/d vitamin D2 or vitamin D3 daily to achieve blood 25(OH)D levels above 30 ng/ml and a maintenance therapy of 1500-2000 IU/d. (5) High dose vitamin D (2-3 times the dose, at least 6000-10000 IU/d) is recommended for obesity, malabsorption syndrome and those taking drugs that affect vitamin D metabolism. (at least 6,000-10,000 IU/d) to treat vitamin D deficiency, resulting in blood 25(OH)D levels above 30 ng/ml and a maintenance therapy of 3,000-6,000 IU/d. 4. Non-blood calcium benefits of vitamin D Vitamin D supplementation is recommended to prevent declining levels. Supplementation with vitamin D above the recommended daily requirement to prevent cardiovascular disease, death, or improve quality of life is not recommended.