Despite going out in the sun often & forgetting sun screen I had very low to none of vitamin D according to my thorough blood work ordered by my gifted doctor at the local Pain Clinic.  I was given a prescription for 50,000 iu's 1 pill once a week for 2 weeks.  Surprisingly my calcium level showed normal.  I said I didn't understand since I was diagnosed in my mid 20s with osteoporosis but apparently the vit. D deficiency could be the cause of the osteoporosis, not lack of calcium.  Until this blood work reveled these findings all previous doctors automatically prescribed extra calcium for me to take. The gel like pills taken over the course of 2 weeks were tollerable without side effects.