Abstract : Studies have found that daily oral 5000 IU vitamin D3 is safe to avoid insufficiency, recover from insufficiency, and avoid toxicity. Thus, this study would like to support the findings that daily oral dose of vitamin D3 for 5000 IU is still safe by following up patients who take daily oral 5000 IU vitamin D3 for four years in various diseases. 14 subjects with various diseases were recruited for this study. Subjects were administered oral vitamin D3 5000 IU daily with informed consent and blood vitamin D level was tested on study entry and follow-up. Subjects were divided into 2 groups based on their blood vitamin D level test follow-up time. The first group consisted of 12 subjects who were followed up once in the range of 1-4 years. The second group consisted of 3 subjects who were followed up every year for 4 years. One subject was included in both groups. The first group who were followed up once in the range of 1-4 years did not have a significant increase in 25(OH)D serum concentration and did not reach toxicity level. The second group which was followed up every year for 4 years had their 25(OH)D serum concentration increased but the increase was also affected by the disease they had. Daily oral 5000 IU vitamin D3 dose is safe proven by 25(OH)D serum concentration not passing 100 ng/ml which is still below 150 ng/ml, where adverse effects are usually present.