Question: I’m having a hard time keeping my vitamin D levels high enough. I have been taking 50,000 IUs of vitamin D3 per week for over year, but still my level is very low with a reading of 6. What can I do?

Dr. Hibberd's answer:
Has the cause of the low level of vitamin D been identified? Generally, persons who may be at a high risk for vitamin D deficiencies include the elderly, obese individuals, exclusively breastfed infants, and those who have limited sun exposure.
Also, those who have fat malabsorption syndromes (e.g., cystic fibrosis) or inflammatory bowel disease (e.g., Crohn's disease) are at risk. Vitamin D3 has been used in various conditions, and for deficiency at least 1,000 IU (25 micrograms) of vitamin D has to be taken by mouth daily (or 8,400 IU of vitamin D3 weekly). Doses higher than the recommended daily allowance are sometimes used to treat vitamin D deficiency, but these are given only under the care of a doctor and only for a short time. A report from Johns Hopkins has suggested that there is conclusive evidence that inadequate levels of vitamin D, carries a substantially increased risk of death from cancer and heart disease, so optimal levels are necessary.

A recent (2010) study has indicated that ingesting vitamin A, in the form of retinol could negate the effect of supplementing with vitamin D, even with levels as low as 3,000 IU/day. Are you also taking vitamin A? If so, it could be interfering with the vitamin D3 supplementation.

Please consult your doctor and raise these queries to find why your vitamin D levels could still be low.