From stronger bones to a better mood, even more efficient weight loss, the benefits of vitamin D ring loud and clear. Recent studies even show vitamin D deficiency can be blamed for everything from cancer and heart disease, to diabetes.

Three-quarters of U.S. teens and adults are deficient in vitamin D,  but how do we know when we’re too low? Here are some signs to look for:

A rise in your blood pressure could mean “D” deficiency. Vitamin D helps regulate blood pressure, so when you don’t get enough, it can creep up.

Sleepiness is another sign. In a 2012 study, lower levels of vitamin D were linked to higher levels of daytime sleepiness.

Also, before you blame your grouchiness on your spouse, your kids, or PMS, know that vitamin D affects serotonin levels in your brain, which impacts your mood.

Fight deficiency by eating more foods high in vitamin D like fish, salami, or eggs. For a meatless way to get your nutrients, try cereal, mushrooms, or soy products.