Do You Have a Vitamin D Deficiency? Answer These 5 Questions to Find Out

You’ve probably heard about vitamin D, the nutrient du jour. The rock-star mineral has more tricks up its sleeve than the new iPhone 7; it can strengthen bones, keep blood pressure in check, protect your ticker, help you shed a few pounds, and may even protect against certain cancers, including breast, ovarian, and colon. (Damn, Gina!) But worryingly, most of us aren’t getting enough. According to Harvard University, an estimated one billion people worldwide have sub-par levels. And it may be even harder to get your fill in the coming months, since shorter days means your body has less time to manufacture the nutrient from the sun.

The Institute of Medicine has set the recommended dietary allowance (RDA) of vitamin D at 600 international units (IU), but many experts believe that’s too low. “Women should take in up to 5,000 IU of vitamin D a day,” says Michael F. Holick, M.D., Ph.D., professor of medicine, physiology, and biophysics at Boston University Medical Center and author of The Vitamin D Solution.

Problem is, many don’t know they’re not hitting their vitamin D goals, since symptoms of low levels can fly under the radar or masquerade as signs of other illnesses. So how do you know if you’re lacking? If you reply “OMG, that’s me!” to any of the questions below, ask your doctor for a simple blood test to check your levels.