Vitamin D is a fat-soluble vitamin that is naturally present in some food and is produced by the skin when it’s exposed to the UV rays in sunlight. Vitamin D helps build and maintain strong bones, helps your body absorb calcium, and balances calcium levels in the blood. Symptoms of vitamin D deficiency can include muscle weakness, pain, fatigue and depression.
A simple blood test can tell your doctor if you have too much or too little vitamin D in your body.