Normal levels are about 30, but some physicians recommend a higher level. Vitamin D3 supplements are available without prescription. You can take 1000 mg to 2000 mg a day orally without contraindications. Prescription doses of 50,000 mg are available to take once a week.
My Vitamin D was 20 and my Dr. has me taking 10,000 iu's of over the counter D-3 daily plus a prescription. It's hard on the stomach so I take 5,000 iu's twice daily. I have it checked again in 6 months.