What is vitamin D deficiency?

Vitamin D deficiency means your body does not have enough of this vitamin and this can have adverse effects on your body.
Approximately 35% of adults in the United States have vitamin D deficiency disease.
Worldwide, vitamin D deficiency is a common issue with about one billion people in the world suffering from it. About 50% of the global population has vitamin D insufficiency.
Normal values of vitamin D in the blood are 75-100 nmol/L (30-40 ng/ml). Vitamin D deficiency is when your serum hydroxyvitamin D levels are less than 50nmol/L (20 ng/ml), and in insufficiency, the levels are 50-75 nmol/L (20-30 ng/ml).
Vitamin D is an essential micronutrient, a vitamin hormone that your body has and uses for a variety of functions.
These include the development of bone, and a positive role in the nervous system, immune system, and musculoskeletal system.
Most importantly, it is a fat-soluble vitamin that helps the body absorb and retain calcium and phosphorus, both being crucial for building bone.
There are three ways your body can get this vitamin.

  1. Through exposure to sunlight where the cholesterol in your skin cells converts the UVA and UVB rays of the sunlight into vitamin D
  2. Through vitamin D foods that you eat
  3. Vitamin D supplements

In spite of these available ways to get vitamin D, you may still acquire its deficiency.

Causes and risk factors of vitamin D deficiency

There are several reasons why you can develop vitamin D deficiency.

  • You are not getting enough exposure to sunlight or if you are, your body isn’t properly converting the sun rays to vitamin D.
  • You are not getting enough vitamin D from the foods, you eat or if you are, your body isn’t absorbing it. This could be due to medical conditions such as malabsorption syndrome.
  • Due to some pathology, your liver or kidneys are not converting vitamin D into its active form.
  • Certain medications you are taking could be interfering with your body’s process of absorbing or converting Vitamin D.
  • Old age is another natural factor that can increase your risk of deficiency.
  • Dark skin indicates more of the pigment melanin, which can reduce your body’s ability to synthesize vitamin D from sunlight.
  • Certain medical conditions that lead to vitamin D deficiency include:
    • Cystic fibrosis, Crohn’s disease, and Celiac disease are conditions that interfere with the absorption of vitamin D from your food or supplements especially if left untreated.
    • Diseases of the liver and the kidneys can reduce the number of enzymes that are responsible for converting vitamin D into its active form, which the body uses. A lack of either of these enzymes leads to an inadequate level of active vitamin D in your body. These enzymes are hepatic enzyme 25–hydroxylase from your liver and 1-alpha-hydroxylase from your kidneys.
    • Obesity is associated with vitamin D deficiency. Because vitamin D is fat-soluble, obese people with higher amounts of body fat will isolate and seize vitamin D in fat cells, which leads to lower amounts of the vitamin circulating in the blood.
    • Weight-loss surgeries reduce the size of your stomach. This makes it difficult for sufficient quantities of certain nutrients, vitamins, and minerals to be absorbed into the blood.
  • Certain medications can lower vitamin D levels, including:
    • Laxatives
    • Steroids
    • Cholesterol-lowering drugs (such as cholestyramine and colestipol).
    • Drugs to control seizures such as phenobarbital
    • Rifampicin given for tuberculosis
    • Orlistat prescribed as a weight-loss drug

Symptoms and signs of vitamin D deficiency

Severe lack of vitamin D in children causes rickets in children. Symptoms of rickets in children include:

  • Incorrect growth patterns due to bowed or bent bones
  • Bone pain
  • Muscle weakness
  • Muscle pain
  • Joint deformities

Lack of vitamin D isn’t so obvious in adults. You may have no symptoms. When present, signs and symptoms in adults include:

  • Fatigue
  • Bone pain
  • Muscle weakness, muscle pain, or muscle cramps

Vitamin D deficiency has been linked to a number of neurological problems, including:

What problems does vitamin D deficiency cause?

The most serious complications of vitamin D deficiency are low blood calcium (hypocalcemia), and low blood phosphate (hypophosphatemia). This leads to:

  • In children, it can cause rickets. Rickets is a rare bone disease that causes the softening of the bones, which then tend to bend.
  • In adults, vitamin D deficiency can cause loss of bone density, which can lead to osteoporosis and easy fractures.
  • In adults, severe vitamin D deficiency leads to osteomalacia, which causes weak bones, bone pain, and muscle weakness.
  • Vitamin D deficiency can also accelerate the risk of fractures and falls in elderly people.

Low blood levels of the vitamin have also been associated with the following health problems:

  • Increased mortality risk from cardiovascular disease
  • Cognitive impairment especially in older adults
  • Asthma in children
  • Increased cancer risk


If you have certain risk factors or symptoms of vitamin D deficiency, your health provider may order a test for vitamin D blood levels.
There are two types of tests that he might order, but most commonly he will test for 25-hydroxyvitamin D, known as 25(OH)D for short.
In adults, you have vitamin D deficiency when your serum 25-hydroxyvitamin D level of less than 20 ng per mL (50 nmol per L).
You are said to have vitamin D insufficiency when your serum 25-hydroxyvitamin D level of 20 to 30 ng per mL (50 to 75 nmol per L).


Vitamin D deficiency does not require any specific drugs to counter it. The aim of treatment is to first achieve and then maintain adequate blood levels. All it requires is to give your body this vitamin in the required doses:

  • Firstly, in higher doses to fill in the deficit and
  • Then, in maintenance doses to sustain the normal levels throughout

Besides advising you of proper sunlight exposure and a rich vitamin food diet, your health provider will likely prescribe vitamin D supplements.

Best practices for sunlight exposure

According to the National Institutes of Health, you require between 5 and 30 minutes of sunlight exposure between 10 a.m. and 3 p.m. two to three times every week. Preferably, the best time to get an optimal amount of vitamin D is noon.
Exposure will be best if your upper torso and legs are uncovered.
How much time you need to expose yourself to sunlight depends on the color of your skin.
According to the Vitamin D Council, people with fair skin need to expose themselves for 15 minutes in the sun, while dark-colored people may need an hour or more.
Following the above recommendations should be enough for your body to produce all of the D3 it needs.

Best foods for vitamin D

Your healthcare provider will also recommend that you incorporate vitamin D-rich foods into your diet.
Few foods are naturally rich in vitamin D3. The best sources include the flesh of fatty fish and fish liver oils.
Egg yolks, cheese, and beef liver contain this vitamin in smaller amounts. Many foods and supplements come fortified with vitamin D like dairy products and cereals.

A list of foods that contain vitamin D include
• Cod liver oil
• Fatty fish like Salmon, Swordfish, Tuna fish, Sardines
• Beef liver
• Egg yolk
• Some foods come fortified with vitamin D. They include:

    • Orange juice fortified with vitamin D
    • Dairy and plant milk fortified with vitamin D
    • Fortified cereals

With the exception of fatty fish, most foods, including fortified dairy products, contain very little amount of vitamin D.

Vitamin D supplements

Vitamin D supplements become necessary to correct the vitamin D deficiency promptly.
The two commonly used vitamin D supplements are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
D2 (ergocalciferol) comes from plant sources, while D3 (cholecalciferol) comes from animals and sunlight.
You need a prescription to get D2, while D3 is available over the counter.
Vitamin D3 supplements are commonly recommended because vitamin D3 raises and sustains vitamin D levels more effectively.
Treatment for vitamin D deficiency should also include supplementing

  • 1000 mg of calcium per day for premenopausal women and men, and
  • 1200 mg per day for postmenopausal women.

The dose and duration of vitamin D3 supplements depend on your existing blood levels of vit D3.
Update.com has a post that explains this dose and blood level relationship.
Higher-dose treatment is sometimes preferred because the deficiency improves quickly, which is very vital in growing children or people with deficiency.
To correct severe vitamin D deficiency (levels less than <10 ng/mL), a commonly applied treatment is to give a “loading dose” of 50,000 IU of vitamin D orally once weekly for 2-3 months, or 3 times weekly for 1 month
Thereafter, a maintenance daily dose of 800 to 2000 IU is sufficient to keep the vitamin levels normal.

Usually, 1000-2000 international units daily for six to eight weeks is the recommended dose for most adults with deficiency. It is important that you do not go overboard with the supplements, because too much vitamin D can cause toxicity.

Monitoring treatment

It is necessary to monitor Vitamin D3 levels when being treated for vitamin D deficiency.
In adults, a test is indicated to monitor blood levels of 25(OH)D three months after beginning treatment.
Accordingly, the dose of vitamin D may need to be adjusted to confirm that normal levels result from the adjusted dose.

How long does it take to recover from vitamin D deficiency?

Generally, how long it takes to fill in the deficiency depends on how low your vitamin D levels were. With the right doses of vitamin D supplements, your vitamin D levels can improve in three to four months’ time.
Similarly, during such time, the bones start to recover and symptoms such as pain begin to improve.

Each 1,000 IU of vitamin D3 taken daily raises blood levels of 25(OH)D by 10 ng/ml after a few weeks. However, it may take months to relieve symptoms of severe vitamin D deficiency such as those seen in rickets in children.

Again, conditions such as obesity and malabsorption syndromes can increase the time it takes for vitamin D supplements to increase vitamin D levels.