Q: I've read your articles on the importance of vitamin D, but I'm wondering how I can tell if my levels aren't high enough?

JVW: There are a few signs your body will send you if you're deficient in this essential nutrient.

Some -- but not all -- individuals with vitamin D deficiency develop pain in the bones, technically referred to as osteomalacia. This is fairly easy to detect on your own by pressing your thumb or forefinger into your sternum (the bone in the center of your chest), your shinbone, or your forearm bone. If it feels especially uncomfortable or painful when you press it, it's a good idea to check with a skilled natural medicine physician to determine your actual vitamin D levels and raise them if necessary.

And don't forget that teeth are bones too. If you have sensitive, aching, or "throbbing" teeth, this might also be a sign you need more vitamin D.

Nearly all the research on vitamin D describes "head sweating" as another sure sign of deficiency. Although this symptom occurs more often at night, it can happen any time and is often profuse. In other words, if you have this problem, most likely, you'll know it. Another body clue to vitamin D deficiency is "hurting hair" -- pain in the scalp when hair is combed or brushed. These two clues are more likely to occur in small children, but they can appear in adults, too.

How much vitamin D should you take if you notice any of these problems? For children, I recommend that reliable grandmother's remedy, cod liver oil. The average teaspoonful contains 400-500 IU of vitamin D, so give this small amount to the very littlest ones. For ages 3 to 8, 2 teaspoonsful daily is a better amount, and for those 8 and up, 1 tablespoonful daily should do the job. For adults, I also recommend that tablespoonful of cod liver oil daily, with enough additional vitamin D (on days you get no sun exposure) to make a daily total of 4,000 IU.