Vitamin D deficiency is common and occurs in both adults and children. Vitamin D deficiency is a serum level of less than 20 ng per ml of 25-hydroxyvitamin D. Vitamin D insufficiency has been defined as a serum level of less than 30 ng per ml.
Recent evidence suggests that 25-hydroxyvitamin D levels of greater than 50 ng/ml (or especially greater than 60 ng/ml) are associated with potential adverse defects.
The symptoms of vitamin D deficiency include muscle pain, muscle weakness, bone pain, low back pain. There is also some evidence that a low Vitamin D level can increase a person’s risk of falls, and increase the risk of some cancers. There is an association between low serum vitamin D levels and some autoimmune diseases, diabetes, and osteoarthritis. Vitamin D deficiency may be associated with depression.
We diagnose vitamin D deficiency with the serum 25 hydroxvitamin D level. There is another blood test available that measures the active form of vitamin D, 1,25-dihydroxyvitamin D. For some complex physiologic reasons, that level, the 1,25 dihydroxvitamin D is not an accurate measure of the body’s vitamin D supply (for details see the Institute of Medicine’s 2011 book DRI Dietary Intake: Calcium and Vitamin D at https://books.nap.edu/openbook.php?record_id=13050).
So, again, if Vitamin D deficiency is a possibility, you should obtain a serum 25-hydroxvitamin D level.
If vitamin D deficiency is diagnosed (25-hydroxvitamin D level of less than 20 ng per ml) then the usual treatment is 80,000 units of vitamin D2 (ergocalciferol) per week for eight weeks. We then recheck the 25-hydroxvitamin D level to see if it has normalized. If it has normalized we go to maintenance therapy. If it hasn’t normalized then we would repeat the treatment for another eight weeks and recheck again. If still low, malabsorption may be the problem, and a GI evaluation is indicated.
It is important to remember that even if there is adequate vitamin D body levels and adequate vitamin D intake, you must have adequate calcium intake for vitamin D to work.
The recommended daily allowance of calcium is at least 1000 mg per day for adults. Some adults need 1200 mg per day. There are two forms of calcium pills: calcium carbonate and calcium citrate. Calcium citrate is the preferred form, I believe, because it is more easily absorbed. To learn more about calcium see Calcium dietary fact sheet from the National Institutes of Health at
The recommended daily allowance of vitamin D for for adult men and women up to 70 years of age is 600 International Units. For men and women 71 years of age or greater, the recommendation is 800 units per day of vitamin D. See the vitamin D dietary fact sheet at
There are two forms of vitamin D supplements: Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The two forms are equally effective and the vitamin D recommendations are the same for both.