Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body's liver and fatty tissues. Vitamin D acts as both a vitamin and a hormone. Two of the main sources of vitamin D are food and sunlight. The ultraviolet rays of the sun react with cholesterol present on the skin and create previtamin D3. This compound goes through a series of reactions involving the kidneys and the liver. The final product is vitamin D.
Vitamin D deficiency describes low levels of vitamin D in the blood. This condition can lead to a condition known as rickets in children. In adults, it can lead to osteomalacia . These are two forms of bone diseases that weaken bones. It is important to contact your doctor if you think you have vitamin D deficiency.
Vitamin D deficiency can be caused by:
- Inadequate intake of vitamin D in the diet
Lack of sunlight due to:
- Having a darker skin color
- Wearing clothes that cover most of the skin
- Living in northern latitudes during the winter
- Not being exposed to direct sunlight—Sunlight through windows, clothes, or sunscreen-covered skin is not enough for the body to synthesize vitamin D.
- Conditions and procedures that affect the body’s ability to absorb vitamin D from the digestive tract (eg, celiac disease , inflammatory bowel disease , bariatric surgery)
Conditions or medicines that affect the process of converting vitamin D to a form that the body can use, such as:
- Anti-seizure medicines such (eg, phenobarbital , phenytoin , carbamazepine )
- Other medicines (eg, rifampin , isoniazid , theophylline )
- Severe liver disease
- Chronic kidney disease
- Vitamin-D dependant rickets (an inherited condition)
- Hypoparathyroidsim (underactive parathyroid)
- Nephrotic syndrome (kidney condition)
- Peritoneal dialysis
Risk factors include:
- Limited sun exposure
- Darker skin color
- Kidney disease
- Restricted activity (eg, due to hospitalization)
- Injury due to a severe burn
- Malabsorption disorder (eg, celiac disease)
- Certain types of diets (eg, macrobiotic diet)
- Liver conditions
- Babies who are breastfed or do not consume enough formula that is fortified with vitamin D
Wearing sunscreen may be a risk factor for vitamin D deficiency. But, organizations like the American Academy of Dermatology (AAD) recommend that you use sunscreen to protect your skin from UV exposure, a known risk factor for skin cancer.
If your vitamin D deficiency is mild to moderate, you may not have any symptoms. If you have a severe deficiency, you may experience:
- Bone and muscle pain
- Muscle weakness
- Hip pain
- Difficulty walking, walking up stairs, and getting out of a chair
Your doctor will ask about your symptoms and medical history. Tests may include the following:
- Blood tests to check vitamin D levels and kidney function
- Bone tests
Talk with your doctor about the best plan for you. Treatment options include:
- Vitamin D supplementation—High doses of vitamin D are given for 6-12 weeks. This is followed by a lower dose of the vitamin. The doses are continued until blood levels return to normal.
- Calcium supplementation—Calcium plus vitamin D supplements may be given to increase D levels. This can also improve bone strength in older women with low vitamin D.
- Light therapy—Exposure to sunlight or UV radiation can increase D levels. Vitamin D3 is produced in the skin when it is exposed to these light sources.
To prevent vitamin D deficiency, take these steps:
- Eat a healthy diet. Foods are not naturally high in vitamin D. Many foods are enriched with vitamin D, such as milk, juices, and cereal.
- Take a vitamin D supplement if recommended by your doctor. Your baby may need a supplement if he is breastfed or does not consume enough formula that is fortified with vitamin D. Children may also need to take a supplement if they are not getting enough vitamin D in their diets.
- Follow your doctor’s guidelines on getting enough sun exposure.
- If you or a family member has any of the above risk factors, talk to the doctor about other ways to avoid becoming deficient in vitamin D.
- Reviewer: Daus Mahnke, MD
- Review Date: 10/2012 -
- Update Date: 10/31/2012 -