Getting a blood test is one of the best ways to see what your body is lacking. Rodgers adds, “But there are many signs and symptoms that you can look at to lead you in the right direction. For example, if you experience chronically tight muscles, heart arrhythmia, restless legs, or even extreme cravings for chocolate, you may be deficient in magnesium. Or, if you are feeling depressed, super fatigued, losing some of your hair, or have muscle weakness, you could be experiencing low vitamin D.”