Estimates are that three-quarters of U.S. teens and adults are deficient in vitamin D.

We all know we need it, 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.