Yes, Arachitol Nano (Vitamin D3) is highly effective and appropriate for treating your severe Vitamin D deficiency. It is typically taken once weekly for 8 weeks, though your doctor will provide the exact schedule. For heavy periods due to a bulky uterus, medical options include Tranexamic acid (taken during menses to reduce bleeding) or hormonal treatments like progestins, oral contraceptives, or a Mirena IUD. Since you are managing diabetes and thyroid issues, please consult your gynecologist. They will select the safest medication and evaluate the cause of your bulky uterus, such as fibroids or adenomyosis.