You walk in the sunshine every day (wearing your SPF, of course). You eat right. You get enough sleep. But you still may be missing something even if you’re doing all the right things—vitamin D. Though rare, severely low levels of vitamin D can cause rickets in children and osteomalacia (softening of the bones) in adults. Left untreated, these conditions can lead to bone pain, and thin, brittle, or misshapen bones, according to the National Institutes of Health. But recent research has suggested a connection between even moderately low levels of vitamin D and a number of surprising health conditions, including diabetes, osteoarthritis, and cancer. There are a number of sneaky signs that can point to a vitamin D deficiency, so if you’re suffering from any of them, talk with your healthcare provider, who will likely recommend a blood test. This is really the only way to accurately determine your vitamin D level. Then you can discuss ways to boost them, usually by taking an over-the-counter supplement.