How to find out if you are getting enough.
If you live in the northwest, it is pretty much a given that your body needs more D than it’s getting. Next time you are seeing your doctor, ask for a vitamin D test. They’ll take a blood sample and get back to you. Serum concentrations of 25-hydroxyvitamin D (also known as 25(OH)D) is the best indicator of vitamin D status. Your 25(OH)D result tells you about the status of your vitamin D concentrations from food and sun combined. The IOM uses 20 ng/mL as the cutoff for determining deficiency. It is very common to have a value lower than 20 ng/mL when you live in the Northwest.
Supplementing with D.
Supplemental vitamin D comes in two forms: D2 (ergocalciferol) and D3 (cholecalciferol). While each form is made differently, they both effectively improve vitamin D status when taken as a supplement or added to fortified foods. When shopping for a vitamin D supplement, look for 1000 IU of either D2 or D3.
Choose wisely – not all supplements are created equal. The Food and Drug Administration (FDA) does not regulate supplements, so it is very difficult to know how pure a product is, not to mention whether or not it is contaminated. When you see a “USP” (this stands for United States Pharmacopeia) seal on the front of the supplement bottle, you can be assured this is a solid supplement. It is possible to overdo the D, so be sure that between your food sources of vitamin D and your supplement, you are getting no more than 2000 IU per day.