The dosage of vitamin D-2 50,000 international units requires a case-by-case determination, including whether the individual is obtaining the vitamin from other sources such as fortified foods and prescription and nonprescription medications, states Drugs.com. Doctors give 50,000 international units orally once weekly for three months for fibromyalgia, notes Mayo Clinic.
Vitamin D-2, known as ergocalciferol, treats many illnesses and conditions, according to Mayo Clinic. Dosages vary depending on the condition a doctor is treating. To treat rheumatoid arthritis, doctors may administer 50,000 international units of vitamin D per week orally for 12 weeks and give patients 50,000 international units daily for six weeks for a vitamin deficiency. Physicians administer ergocalciferol orally in doses of 50,000 to 200,000 international units per day in addition to 4 grams of calcium lactate six times per day to treat low parathyroid gland activity.