What should I do if my total 25 hydroxyvitamin D is low? It can be supplemented in the following ways: First, oral supplementation with 25 hydroxyvitamin D2 or D3, with a recommended daily supplementation of 5,000 units for 2-3 months, and re-checking the level of 25 hydroxyvitamin D. If it reaches within the normal range, it can be supplemented with 800 units per day or 5,000 units per week. Second, intramuscular injection of vitamin D2 or D3 300000 units for supplementation, supplementation once a month for 2-3 months, after the vitamin D level reaches the normal range, supplementation 800 units per day or about 5000 units per week. In addition to medication supplementation, patients can also supplement by increasing the time of light exposure and taking more vitamin D containing foods.