1000 IU of Vit D/day won’t be enough for my patients who are severely insufficient

The daily vitamin D requirement is at least 400 – 800 IU (10 – 20 micrograms), though most vitamin D does not come from food. If sun exposure is not possible, then a vitamin D supplement of at least 800 IU per day is recommended. A larger dose (5000 – 10,000 IU [125-250 micrograms]) per day may be needed for some weeks to treat people with severe insufficiency.3 Ongoing treatment with a lower dose (e.g. 1000 IU per day) is then recommended.