If you were diagnosed with "severe" vitamin d deficiency
, your 25ohd level would usually be <20 ng/ml.
For this, your doctor can treat you with 50, 000 iu d3 orally once per week for 6-8 weeks. This could be followed by taking 1000-2000 iu per day, with a re-test @ 3-4 months to see where you are. If the reason for vit d deficiency is poor absorption, your needs may differ. Ask your doctor.