Vitamin D Deficiency: Causes, Treatment & Prevention

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Vitamin D is a fat-soluble vitamin that is naturally occurring in some fruits and foods. Your skin also produces vitamin D, when you are in the sun. It is essential for the proper functioning of many body parts. Its most important role is to keep your bones healthy by increasing your body’s ability to absorb calcium.  

When your body doesn’t get an adequate amount of vitamin D, your bones might become thin and brittle. Making you more susceptible to fractures. Vitamin D also plays a role in preventing and possibly treating diabetes, high blood pressure, some types of cancer, and multiple sclerosis.

Signs of Low Vitamin D 

The most common sign of vitamin D deficiency is muscle weakness and bone pain. Some other symptoms of low vitamin D levels include: 

  • Weakness 
  • Mood swings 
  • Fatigue 

Vitamin D deficiency can cause osteoporosis which causes your bones to fracture easily. In children, it can cause rickets, a condition that causes the bones to become soft and bend.

Severe vitamin D deficiency can also cause a condition known as osteomalacia in adults. Osteomalacia causes muscle weakness, bone pain, and weak bones. 

Causes of Low Vitamin D 

A variety of factors varying from medical conditions to aging might be responsible for low Vitamin D levels. 


As you age, the skin’s natural ability to produce Vitamin D decreases, this contributes to vitamin D deficiency in older people. It is thought that by the age of 70, there can be as much as a 25% reduction in your skin's vitamin D production.

Weight Loss Surgery

People who undergo weight-loss surgeries to reduce the size of their stomachs might be more susceptible to developing a vitamin D deficiency. This is because it becomes harder for them to consume the vitamins they need in sufficient quantities.

Insufficient Exposure to Sunlight

Your skin makes use of sunlight to produce vitamin D and when you have little or no exposure to the sun it can’t do that. This means you’d have to rely on only dietary supplies of vitamin D which can be insufficient for your body. People with darker skin also find it a little more difficult to produce vitamin D.

Your Diet Doesn’t Contain Vitamin D

It’s very important to ensure that our diet always contains all the vitamins and nutrients our bodies need to function properly. Fish, egg yolks, milk, and liver are excellent sources of vitamin D.

People who have vegan diets find it more difficult to incorporate vitamin D into their diets as some of the richest sources of vitamin D are animal-based.

Vitamin D dietary supplements are a great option for people with this problem. Orange juice also contains a substantial amount of vitamin D.

Some medical conditions could also cause vitamin D deficiency, some of them include: 

  • Kidney diseases 
  • Liver diseases 
  • Obesity 
  • Celiac disease 
  • Crohn’s disease 
  • Cystic fibrosis

Diagnosing Vitamin D Deficiency

Symptoms of vitamin D deficiency are common symptoms of many other conditions. To ensure that vitamin D deficiency is indeed the underlying cause of your symptoms, your doctor will typically recommend a 25-hydroxy vitamin D blood test.

This test helps measure the levels of vitamin D in your body. If your levels are less than 12 nanograms per milliliter, you will be diagnosed with vitamin D deficiency.

Who Is at Risk?

Certain factors asides from your diet increase your likelihood of developing vitamin D deficiency. Some of them include: 

  • Those who are obese may be deficient in vitamin D because body fat can bind to vitamin D and prevent your body from absorbing it
  • People with darker skin are less able to create sufficient amounts of vitamin D in their skin
  • Pregnant and lactating women may be more prone to vitamin D deficiency
  • People with fat malabsorption disorders may deal with vitamin D deficiency
  • Infants who are breastfed may have a vitamin D deficiency because breast milk isn’t a great source of vitamin D
  • People who take medicines, like antifungal drugs and anti-seizure drugs, are more prone to vitamin D deficiency because these medicines can affect the metabolism of vitamin D

Treatment For Low Vitamin D 

The focus of treating vitamin D deficiency is raising your vitamin D levels to a point where it’s adequate for normal body functioning. This can be done in a variety of ways including: 

  • Taking vitamin D supplements will help boost your vitamin D levels. Vitamin D supplements are available in two forms—D2 and D3. D2 is also known as ergocalciferol and is derived from plants. While D3 is also known as cholecalciferol and is derived from animals. D3 supplements are available over the counter, but a prescription is needed to get D2 supplements. 
  • Eating foods that are rich in vitamin D such as cod liver oil, swordfish, tuna, salmon, milk, and liver. For people with vegan diets, a cup of orange juice is also a great source of vitamin D.
  • Getting more sunlight safely by applying a broad-spectrum sunscreen before going in the sun. 10 to 15 minutes of sun exposure, two to three times a week may be adequate for your skin to absorb enough vitamin D. If you have darker skin or are older you might want to spend some more time in the sun. 

It is typically recommended for adults to get at least 600 international units (IUs) of vitamin D per day either through your diet or nutritional supplements.

For older people, 800 IUs is recommended as their skin slows the production of vitamin D with the sun.

Infants should be getting at least 400 IUs and pregnant and breastfeeding women should be getting at least 600 IUs. However, people who are at a higher risk of developing vitamin D deficiency may need more than these recommended units. 

A Word From Verywell

It is certainly more difficult to treat vitamin D deficiency than to prevent it. Eating foods rich in vitamin D, using vitamin D supplements, and getting adequate sunlight is a great way to prevent low vitamin D levels in your body.

But be careful about your vitamin D intake, it is possible to consume too much vitamin D. Even though vitamin D overdose is rare, you shouldn’t take higher than your daily recommended dosage of vitamin D without speaking to your doctor first. Signs of vitamin D overdose include nausea, constipation, weakness, and weight loss.

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