What Is Vitamin D Deficiency?

Vitamin D deficiency is a condition characterized by your body not getting or processing enough vitamin D. You can get vitamin D from sunlight, from certain foods, and in supplement form. Vitamin D helps your body absorb calcium to rebuild and strengthen bones. The vitamin also supports your immune system, muscle health, and nervous system.

About 1 billion people worldwide and one-third of adults in the United States have vitamin D deficiency. Infants have higher rates of vitamin D deficiency, particularly in Middle Eastern countries. The condition can be diagnosed with a blood test and is often curable and preventable. 

Common causes include not getting enough vitamin D from your diet, supplements, or skin absorption from the sun. A vitamin D deficiency can also be caused by reduced absorption, which can occur due to certain medications or from issues with your liver or kidneys. Treatment options could include changing medications, taking supplements, or adding more vitamin D-rich foods to your diet.

Vitamin D Deficiency Symptoms

Vitamin D deficiency symptoms can vary depending on how deficient you are. A majority of people with vitamin D deficiency are asymptomatic, meaning they do not experience symptoms. However, prolonged vitamin D deficiency can cause hypocalcemia and hyperparathyroidism. 

Hypocalcemia is when the level of calcium in your blood is too low. This is usually asymptomatic but can contribute to long-term health issues such as osteoporosis, which is when your bones are less dense, making them fragile and at higher risk of fracture.

Hyperparathyroidism is when one or more of the glands that make parathyroid hormone (PTH) overactive. Long-term hyperparathyroidism can also cause hypocalcemia. Symptoms include fatigue, muscle twitching, weakness, and bone, joint, and muscle pain.

What Causes Vitamin D Deficiency?

Vitamin D deficiency occurs when your body either doesn’t get enough vitamin D or it can’t be absorbed in your cells due to medications that interfere with the process.

The two most common forms of vitamin D are D2 and D3: 

  • D2 is consumed through plant and yeast sources—especially mushrooms. 
  • D3 generally comes from animal products such as milk, fish, and eggs. Eighty to 90% of the vitamin D3 in your body comes from sunlight, although it doesn’t start as vitamin D3. The sun’s ultraviolet rays interact with a protein in the skin to produce the vitamin. Sun exposure without sunscreen should be limited to avoid increasing your risk of skin cancer.  

Risk Factors

Risk factors vary based on the source of vitamin D. Darker skin pigment is a risk factor in vitamin D deficiency from sunlight because darker skin tones may not absorb as much vitamin D as lighter ones. Age is also a risk factor. Both infants and older adults are at a higher risk of not getting enough vitamin D in their diets.


In order to absorb vitamin D, your liver converts it into 25 hydroxyvitamin D, or 25(OH)D. Your kidneys use 25(OH)D to make “active vitamin D,” which helps your body utilize calcium for your bone and cell health. A blood test can be used to check the level of 25(OH)D in your blood, which is regarded as the most accurate way to determine if you are vitamin D deficient. Results are determined by the following readings:

  • Not vitamin D deficient: 25 (OH)D level of 21-50 nanograms per milliliter (ng/mL)
  • Vitamin D deficient: 20 ng/mL or lower
  • Severely vitamin D deficient: 12 ng/mL or lower

There are other indirect signs that you may have vitamin D deficiency. For instance, if there are low levels of calcium in your urine, this could be an indication of low vitamin D levels. Similarly, bone mineral density and bone breaks (fractures) appearing on X-rays may also be a sign to check your vitamin D levels.

Treatments for Vitamin D Deficiency

Treatments for vitamin D deficiency include diet changes and vitamin supplements. In some cases, an oral supplement of 50,000 International Units (IUs) may be prescribed for up to eight weeks. This is substantially higher than the average daily recommendation of 400 IUs for children ages 12 and under, 600 IUs for people ages 13-70, and 800 IUs for people ages 71 and up. The goal is to bring your vitamin D levels into a healthy range and reduce your risk of bone fractures and falls.

Smaller supplements may be taken as your healthcare provider recommends. Diet changes may include adding vitamin D-rich foods to your diet such as salmon, cod liver oil, or egg yolks. 


Vitamin D deficiency often can be prevented in a variety of ways:

  • Eat a balanced diet rich in vitamin D and calcium: Choosing foods that are rich in vitamin D can help you avoid becoming vitamin D deficient.
  • Sunlight: Doing outdoor activities can boost vitamin D levels and boost your activity levels.
  • Medications: Ask your healthcare provider or pharmacist if any of your medications may interfere with vitamin D absorption. You may be able to switch medications now to avoid the possibility of a vitamin deficiency later.
  • Take supplements based on your healthcare provider’s advice: Your doctor should be able to tell you what amount of vitamin D makes sense for you. Since it is possible to have health effects from too much Vitamin D, it is important to take the right dosage.


Long-term vitamin D deficiency can cause a variety of complications, including:

  • Osteoporosis: Experiencing prolonged vitamin D deficiency can reduce your bone density, leading to osteoporosis.
  • Rickets: Vitamin D deficency is the cause of rickets, a childhood condition in which bones soften and bend, often resulting in bow legs.
  • Osteomalacia: This is essentially the adult version of rickets, causing bone softening and a combination of symptoms such as pain and weakness.
  • Malnutrition: This is when the body doesn’t get or absorb enough nutrients. Vitamin D deficiency and malnutrition have an inverse relationship, with one often causing the other. 

Living With Vitamin D Deficiency

Most people with vitamin D deficiency do not experience symptoms or realize that they are vitamin D deficient. Therefore, it’s important to get your annual physical at your healthcare provider’s office and have routine blood work done. Using these measures to can help prevent vitamin D deficiency and, therefore, what can occur should it go untreated. If you are concerned about your vitamin D levels, talk to your healthcare provider about getting a blood test.

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7 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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