You may be taking vitamin D but that doesn't mean your blood levels are at a healthy level. If you haven't had your blood levels of vitamin D checked, you probably should.

Why is vitamin D so important? Vitamin is good for your bones and your body:

• Vitamin D helps you absorb your calcium so it can go to your bones and keep them strong.
• Vitamin D also makes muscles stronger - lowering your chances of falling and breaking a bone.
• Vitamin D may lower the risk of breast cancer, prostate cancer, and others as well.
• Osteoporosis medicines may not work as well when vitamin D levels are not in the healthy range.

Your Maintenance Dose  
You should aim for 1000 IU's to 1500 IU's from any over-the-counter supplements you may be taking (multivitamin, calcium plus D supplements, separate vitamin D supplements).  This 1000 to 1500 IU's is what we call the "maintenance dose".  If your levels are healthy, this is what you need to keep them there.  You will likely need to take a high dose prescription vitamin D for a few months if your blood levels are too low.

Doctors often prescribe a 50,000 IU tablet once or twice a week for 2 to three months to increase your levels to the healthy range. It's usually safe to keep taking your over-the-counter vitamin D even on this high dose, but check with your doctor to be sure.

Get Checked           
The lab test that tells you what your vitamin D levels are is a "25-OH-D" or a "25 vitamin D". Healthy blood levels are 32 ng/ml to 100 ng/ml.  Some labs report 20 ng/ml as normal but the latest studies show that is too low.

Sources:
Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, Dawson-Hughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr 2006;84:18 -28.

Holick MF. Vitamin D Deficiency. N Engl J Med 2007;357:266-81.

Stechschulte SA, Kirsner RS, Federman DG. Vitamin D: bone and beyond, rationale and recommendations for supplementation. Am J Med (2009) 122, 793-802.