Recall reading that once a person reaches the age of 40, their skin makes considerable less D3. That could be part of the problem on why you tested low.
Overall, what I do is take 6000ius of D3 a day in order to reach a testing level between 60 to 70ng/ml. Thought this article explained well what to look for in D3 supplements and how to test.
"Getting vitamin D right"
http://www.trackyourplaque.com/blog/...n-d-right.html
Excerpt from it about age:
Quote:
“I’m going to Florida. I’ll stop my vitamin D because I’m going to lay in the sun.”
Wrong. 90% of adults over 40 years old have lost the majority of their ability to activate vitamin D in the skin. A typical response might be an increase in blood level from 25 to 35 ng/ml–a 10 ng increase with a dark brown tan.
There is an occasional person who, with sun exposure, increases blood levels substantially. This can occur in both fair-skinned and dark-skinned people, though I’ve never seen it happen in an African-American person. The occasional person who maintains the ability to convert vitamin D with sun exposure, or young people, should seasonally adjust their vitamin D dose, e.g., 6000 units winter, 3000 units summer, or some other regimen that maintains desirable blood levels. You can see that monitoring blood levels (we check levels every 6 months for the first 2 years) is crucial: You cannot know what your vitamin D needs are unless you assess 25-hydroxy vitamin D levels.
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