What Is Vitamin D Deficiency?

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Vitamin D is often referred to as the "sunshine vitamin" because it is produced by your body when your skin is exposed to the sun. Since vitamin D helps to keep your bones strong, a deficiency can lead to bone softening and subsequent bone pain and fractures.


What Does Vitamin D Have to Do With MS?

While vitamin D deficiency is unfortunately very common, the good news is that this health condition can be diagnosed with a simple blood test and treated with prescription and/or over-the-counter supplements.

Vitamin D Deficiency Symptoms

Most people with vitamin D deficiency are asymptomatic. Only with a severe and prolonged deficiency do symptoms arise.

The major role of vitamin D is to absorb calcium and phosphorus from the intestines in order to build and maintain bone mass. With vitamin D deficiency, this cannot occur adequately. With a severe deficiency, bone softening (a condition called osteomalacia in adults and rickets in children) may develop.

With osteomalacia and rickets, a person may experience throbbing bone discomfort and muscle weakness and pain. Osteomalacia also increases a person's chances of developing bone fractures, falling, and experiencing walking problems.

Besides bone and muscle symptoms, fatigue and depression are also associated with vitamin D deficiency.


Since you need sun exposure to make vitamin D, the most at-risk populations for vitamin D deficiency include anyone who spends a lot of time indoors (the elderly and the homebound, for example) and people with dark skin (as it absorbs less sunlight than lighter skin).

Other populations at risk for vitamin D deficiency include:

  • Those who do not consume enough vitamin D-containing foods (e.g., canned tuna and fortified cow's milk)
  • Those with diseases that affect the absorption of vitamin D in the gut (e.g., Celiac disease and Crohn's disease)
  • Those with diseases that affect the metabolism of vitamin D into its active form (e.g., chronic kidney or liver disease)
  • Those who are obese (extra fat tissue hides away vitamin D instead of releasing it into the bloodstream)
  • Those who take medications that enhance the breakdown of vitamin D (e.g., antiseizure medications and medicines used to treat HIV)

Interesting Associations

Besides its primary function in calcium metabolism, vitamin D may play a role in reducing inflammation and moderating immune function in the body. This may be why research has found links between vitamin D deficiency and various autoimmune diseases like multiple sclerosis, rheumatoid arthritis, and type 1 diabetes.

Heart disease and cancer have also been linked to vitamin D deficiency. In fact, research has shown that more heart attacks occur in the winter (when people go outside less and therefore have lower vitamin D levels), and that people survive cancer better in the summer (when their vitamin D levels are higher).


If you have one or more risk factors for vitamin D deficiency—for example, if you are obese, or if you have chronic kidney disease or a gut malabsorption syndrome—your doctor should screen you for vitamin D deficiency.

Certain symptoms may also prompt your doctor to test for vitamin D deficiency, such as an increased number of falls, especially if you are elderly.

Screening for vitamin D deficiency in a person without risk factors is not recommended.

A simple blood test called 25-hydroxyvitamin D or 25(OH)D can be used to diagnose vitamin D deficiency.

While there is no definitive consensus about what a normal, healthy vitamin D level is, the Institute of Medicine (IOM) defines it as follows: 

  • Normal: 25 (OH)D level greater than 20 ng/mL
  • Insufficient: 25 (OH)D level between 12 to 20 ng/mL
  • Deficient: 25 (OH)D level less than 12 ng/mL


The treatment of vitamin D deficiency depends on a number of factors, such as the severity of the deficiency and whether certain underlying health problems exist.

That said, in the vast majority of cases, vitamin D deficiency is treated with a supplement.


There are two major forms of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol), the latter of which is used in most supplements.

To date, there is no standard regimen for treating vitamin D deficiency. A typical plan, though, may include taking 50,000 international units (IUs) of vitamin D2 or D3 by mouth once or more per week for eight weeks, followed by 1,500 to 2,000 IUs of vitamin D3 taken daily.

Keep in mind that higher doses will be needed to treat people with medical conditions that affect vitamin D absorption in the gut, and those taking medications that affect vitamin D metabolism.

Vitamin D Toxicity

Excess vitamin D may cause symptoms related to resulting high calcium levels in the blood, such as muscle cramping, constipation, heart arrhythmias, and kidney stones. This is why it is important to only take a vitamin D supplement as directed by your doctor.


Diet is an additional, albeit not robust, source of vitamin D, and therefore not usually recommended for treating a deficiency. That said, it can be useful for maintaining a healthy vitamin D level.

Foods that contain vitamin D include:

  • Fatty fish (e.g., salmon and swordfish)
  • Cod liver oil
  • Nuts
  • Cereals and dairy products fortified with vitamin D
  • Cheese
  • Eggs
  • Mushrooms
  • Beef liver


Sunlight is the third source of vitamin D. As with diet, it is not usually recommended as a treatment for vitamin D deficiency. This is because of the increased risk of skin cancer.


While the amount of vitamin D that a person needs varies based on factors like skin color and sun exposure, general recommendations from the IOM state that individuals ages 1 to 70 should take a supplement containing 600 IUs of vitamin D daily. After age 70, a person should take 800 IUs of vitamin D daily.

These vitamin D preventive recommendations are for the general population—not for people with a diagnosed vitamin D deficiency. People who are deficient in vitamin D require therapeutic doses of vitamin D.

In addition to or in lieu of taking a supplement, your doctor may recommend that you eat or drink foods that contain vitamin D and/or that you get some sunshine (but not too much).

A Word From Verywell

The treatment of vitamin D deficiency is important for keeping your bones strong, and it may improve the health of other systems and tissues in your body like your immune system and heart.

However, before you make big changes, please talk with your doctor about having your vitamin D level checked first. Based on your level and risk factors, you and your doctor can decide what the best treatment plan is for you.

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