An Overview of Vitamin D Deficiency

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In This Article

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 breaks ("fractures").

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.


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 (darker skin absorbs less sunlight).

Other populations at risk for vitamin D deficiency include the following:

  • 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 (the 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).

Symptoms and Complications

The major role of vitamin D is to absorb calcium and phosphorus from the intestines in order to build and maintain bone mass.

Bone and Muscle Symptoms

When vitamin D is deficient, adequate calcium and phosphorous cannot be absorbed within the gut. With a prolonged and severe deficiency, bone softening (a condition called osteomalacia in adults and rickets in children) may develop,

With osteomalacia and rickets, a person may experience bone pain and muscle weakness. They are also at a higher risk of bone fractures and walking problems.

Other Symptoms

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


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).


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 the following: 

  • 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 the following:

Take 50,000 international units of vitamin D2 or D3 by mouth once or more per week for eight weeks followed by 1500 to 2000 international units of vitamin D3 taken daily.

Keep in mind—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 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 under the guidance of 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, and nuts. Cereals and dairy products fortified with vitamin D are additional sources, as is cheese, eggs, mushrooms, and 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 vary based on factors like skin color and sun exposure, general recommendations from the Institute of Medicine state that individuals from age one to age 70 take a supplement containing 600 international units of vitamin D daily. After age 70, a person should take 800 international units of vitamin D daily.

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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Article Sources

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