The only true way to know your vitamin D status, and therefore your proper daily dose, is with a blood test, in which the metabolically-active form of vitamin D, 25-hydroxvitamin D (25-OH-D, or calcidiol) is measured. Relatively recently (over the past 5 to 7 years) when vitamin D’s role in the prevention of degenerative diseases beyond prevention of osteoporosis was recognized, the medical experts recommended a minimum target blood level of 30 ng/ml of 25-hydroxyvitamin D. (I emphasize that “minimum target level” means just that, “minimum!” It does not mean “optimal.”) Therefore, the reference lab ranges was raised to 32 – 100 ng/ml. Most experts in the field of researching and treating vitamin D deficiencies have recommended that “optimal” serum 25-OH-D levels begin at 42 ng/ml, with the ideal target range being achieved between 50 – 80 ng/ml.

What Dose of Vitamin D is Optimal?

The vitamin D dose required to attain a serum level range of 50 – 80 ng/ml will vary from person to person, mostly based upon body mass (weight) and sun exposure. Although this will vary considerably, a 150 lb person who supplements with 2000 IU of vitamin D per day may attain blood level range of 25-OH-D between 30 and 45 ng/ml, depending upon sun exposure. To attain the optimal levels between 50 and 80 ng/ml that same person may need to supplement with 4000 IU per day or more.

On the other hand, a person who weighs 225 lbs. may require 10,000 IU/day to maintain 25-hydroxy vitamin D blood serum levels between 50 and 80 ng/ml. In all instances, the only way to accurately know the “true daily dosage” for a particular person would be to first estimate a starting vitamin D dose, get a serum 25-OH vitamin D test; adjust the dose accordingly, and get re-tested several weeks later.

For more information, read my full article on vitamin D, “D Day: An All-Out Assault on Chronic Disease with Vitamin D” on www.laddmcnamara.com under the “In the News” section.