You probably think about your hair on a daily basis fretting over a bad hair day or enjoying a nice blowout, or maybe wondering whether to try out the new style you noticed on your favorite celebrity. But you might be missing clues that your hair is revealing about your health.

Your hair can let you and your doctor know whether you're stressed, have a nutritional deficiency, a thyroid problem, or other health issues. Here are some key things to look for in your locks.

Vitamin B12

Scientists don't know exactly why some people go gray early, but genes play a large role. Also, a vitamin B-12 deficiency or problems with your pituitary or thyroid gland can cause premature graying that's reversible if the problem is corrected.

Most people get more than enough B12 from eating meat, eggs, milk, and cheese. Normally, the vitamin is absorbed by your digestive system—your stomach and intestines. Vitamin B12 deficiency anemia usually happens when the digestive system is not able to absorb the vitamin.

This anemia can also happen if you don't eat enough foods with B12, but this is rare. People who eat a vegan diet and older adults who don't eat a variety of foods may need to take a daily vitamin pill to get enough B12. Other causes include drinking alcohol and taking some prescription and nonprescription medicines.

Symptoms of vitamin B12

If your vitamin B12 deficiency is mild, you may not have symptoms or you may not notice them. Some people may think they are just the result of growing older. As the anemia gets worse, you may:

Feel weak, tired, and light-headed.

Have pale skin.

Have a sore, red tongue or bleeding gums.

Feel sick to your stomach and lose weight.

Have diarrhea or constipation.

A vitamin B-12 deficiency is associated with a condition called pernicious anemia, which is when your body can’t absorb enough of this vitamin. Your body needs vitamin B-12 for healthy red blood cells, which carry oxygen to cells in your body, including hair cells. A deficiency can weaken hair cells and affect melanin production.

Thyroid disorder

Hormonal changes caused by a thyroid problem — such as hyperthyroidism or hypothyroidism — may also be responsible for premature white hair. The thyroid is a butterfly-shaped gland located at the base of your neck. It helps control many bodily functions such as metabolism. The health of your thyroid can also influence the color of your hair. An overactive or underactive thyroid can cause your body to produce less melanin.

Stress

While graying is mostly genetic, oxidative stress in the body may play a part when the process happens prematurely.

Oxidative stress causes imbalances when antioxidants are not enough to counteract the damaging effects of free radicals. Free radicals are unstable molecules that damage cells, contributing to aging and disease.

Too much oxidative stress can promote the development of diseases, including the skin-pigment condition vitiligo. Vitiligo may also turn the hair white due to melanin cell death or the loss of cell function.

With the right diagnosis and treatments, white hair progression can be stopped and reversed in some instances. A balanced diet and good hair care can also help. In some cases, however, the process is irreversible.