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Vitamin D Deficiency: Causes, Symptoms & Treatment

 - Kolkata

General Physician

Kolkata   |   21 Apr 2023

Vitamin D Deficiency: Causes, Symptoms & Treatment

Vitamin D is classified as a fat-soluble Vitamin and is a secosteroid. It plays a very important role in our body since it helps in the absorption of magnesium, phosphate, and calcium in the intestine. Vitamin D is an essential Vitamin that our body uses for the normal development and maintenance of bones. It also plays a vital role in the nervous system, immune system, and musculoskeletal system.   

When an individual lacks an adequate amount of Vitamin D in the body, he/she is said to be having a deficiency. Vitamin D deficiency is one of the most common deficiencies seen in children as well as adults. The deficiency of Vitamin D results in causing major health disorders and symptoms.

Why is Vitamin D so important?

Vitamin D is sometimes called the sunshine Vitamin because it plays an important role in the proper functioning of the body which includes bone health and immunity. It may even help in preventing and protecting against cancer, bone loss, type 2 diabetes, depression, multiple sclerosis, and heart diseases.  It helps the body to absorb calcium for strong bones, supports nerves to carry messages from the body to the brain and vice versa, plays an important role in muscle movement, and supports the immune system to fight against infections.

How common is Vitamin D deficiency?

Vitamin D deficiency is a common condition that can affect infants, children, adults, and older age groups. As per the research studies, it is estimated that about 1 billion people are affected with Vitamin D deficiency worldwide, while Vitamin D insufficiency is affected 50% of the population.  

How much amount of Vitamin D is required for the body?

The amount of Vitamin D required for the body depends upon the age of the patient. The recommended amount of Vitamin D is:

  • Since birth to 12 months of age: 400 IU
  • Children between 1-13 years of age: 600 IU
  • Teens between 14-18 years of age: 600 IU
  • Adults between 19-70 years of age: 600 IU
  • Older age people > 71 years: 800 IU
  • Pregnant females: 600 IU

Causes of Vitamin D deficiency

The cause of Vitamin D deficiency is listed below:

  • Lack of Vitamin D in the diet
  • Malabsorption of Vitamin D in the diet
  • Lack of sufficient amount of exposure to sunlight
  • Failure of conversion of Vitamin D to its active form by the liver and kidney in the body
  • Intake of medicines that will interfere with the body’s ability to convert or absorb Vitamin D.
  • Patient who underwent weight loss surgery
  • Age-related
  • Lack of intake of fish or dairy products in the diet.
  • Increased hepatic catabolism
  • End organ resistance

Symptoms of Vitamin D deficiency

The symptoms associated with Vitamin D deficiency are listed below:

  • Muscle weakness
  • Bone and back pain
  • Cognitive disorders, especially in the older age group
  • Fatigue and tiredness
  • Frequent illness due to infections
  • Depression
  • Impaired wound healing
  • Bone and hair loss
  • Muscle pain 

What are the complications associated with Vitamin D if left untreated?

The complications associated with Vitamin D if left untreated are:

  • In children it can cause rickets, it is a rare condition, where the bones of the child become soft and bend.
  • In adults, it can cause osteomalacia, a condition where the bones become weak, bone pain present, and muscle weakness.
  • Hypocalcemia (low blood calcium levels)
  • Hypophosphatemia (low phosphate levels)

Diagnosis of Vitamin D deficiency

The diagnosis of Vitamin D can be done by the following tests. They include:

  • Physical examination- During the physical examination, the doctor will examine the patient thoroughly. The doctor will take the medical history of the patient
  • Family history- The doctor will ask the patient, about the family history of Vitamin D deficiency, in order to make sure the patient has a family history of Vitamin D deficiency.
  • 25-hydroxy Vitamin D or calcidiol blood test- it is one of the best and most accurate tests to diagnose Vitamin D deficiency. Normal levels range from 20ng/mL to 50ng/mL. whereas if the concentration is less than 20ng/mL is abnormal and indicates Vitamin D deficiency
  • 1,25 dihydroxy Vitamin D, or calcitriol test
  • Other tests include- serum calcium levels, serum alkaline phosphate levels, fasting serum phosphate, and serum 1,25-dihydroxy Vitamin D test, liver function test, and kidney function test.
  • Bone density (DEXA) scan

Staging of Vitamin D deficiency

Vitamin D deficiency can be staged or classified into three stages

  • Mild deficiency- during this stage, the serum 25-hydroxyVitamin D levels are less than 20ng/mL
  • Moderate deficiency- during this stage, the serum 25-hydroxyVitamin D levels are less than 10ng/mL
  • Severe deficiency- during this stage, the serum 25-hydroxyVitamin D levels are less than 5ng/mL.

Who is at risk of Vitamin D deficiency?

People who are at high risk of having Vitamin D deficiency are listed below:

  • Breastfeeding babies have Vitamin D deficiency since human milk lacks of Vitamin D
  • People with dark skin have an increased risk of having Vitamin D deficiency
  • People who have undergone gastric bypass surgery
  • People who are diagnosed with chronic kidney and liver disease
  • People who are diagnosed with cystic fibrosis, Crohn’s disease, and celiac disease.
  • Obese people
  • People who are taking medications that include- laxatives, steroids, cholesterol-lowering drugs, rifampin, or orlistat
  • Age-related

Treatment for Vitamin D deficiency

The best way to treat Vitamin D deficiency is by rectifying the Vitamin D levels through diet or through supplementation. The required amount of Vitamin D depends on the age of the patient and other health conditions associated with it. A concentration of less than 20ng/mL is generally considered inadequate and requires treatment.

  • Food supplements
  • Exposure to natural sunlight- sensible sun exposure, especially between 10 am and 3 pm, produces Vitamin D
  • Supplements- the supplementation can be given in the form of an oral route or through the intravenous route.
  1. The initial supplementation for a duration of 8 weeks with Vitamin D3 either 6,000 IU daily or 50,000 IU weekly once. Once the serum 25- hydroxyVitamin D levels exceed 30ng/mL, a maintenance dose of 1000 to 2000 IU is recommended.
  2. For Adults who are at high risk of Vitamin D deficiency, a higher dose of Vitamin D3 is recommended in order to treat the underlying causes. A higher dose of 10,000 IU is recommended in such conditions daily until the serum 25-hydroxyVitamin D levels exceed 30ng/mL, followed by a maintenance dose of 3000-6000ng/mL is recommended.
  3. Children who are diagnosed with Vitamin D deficiency require a daily dose of 2000 IU of Vitamin D3 or a weekly once dose of 50,000 IU of Vitamin D3 for a duration of 6 weeks. Once the serum 25-hydroxyVitamin D levels exceed 30ng/mL, a maintenance dose of 1000 IU is recommended.
  4. Calcitriol is recommended for patients who have a persistent deficiency, despite treatment with Vitamins D2 and D3. For patients who are on calcitriol treatment, their calcium levels are closely monitored due to the increased risk of developing hypercalcemia secondary to calcitriol.
  5. Calcidiol is recommended for patients with fat malabsorption or with severe liver diseases

Food sources that are rich in Vitamin D

The food sources that are rich in Vitamin D are:

  • Oily fish such as salmon or mackerel
  • Cheese
  • Egg yolk
  • Beef liver
  • Mushrooms
  • Fortified food includes orange juice, milk, soy drinks, breakfast cereals, and margarine.
  • Other dairy products

Prevention of Vitamin D deficiency

Vitamin D deficiency can be prevented by following the below-mentioned steps strictly.

  • Taking supplements of Vitamin D regularly
  • Spending more time under the sun, in order to allow our skin to absorb a greater amount of Vitamins. Consult a dermatologist before getting exposed to sunlight, since too much exposure is harmful to the body.
  • Ensure that you add an adequate amount of Vitamin D to the diet.
  • Maintain a healthy weight
  • Becoming proactive about preventive health.

What are the effects of an excessive amount of Vitamin D in our bodies?

The side effects associated with an excessive amount of Vitamin D in our body are:

  • Hypercalcemia- it is a condition where there is an excess amount of calcium build-up in our body, which can lead to complications such as frequent urination, weakness, vomiting, formation of calcium stones in the kidney, irregular heart rate (arrhythmias), and confusion.
  • Excessive amounts of Vitamin D can result in toxicity, which can cause complications such as weight loss, fatigue, poor appetite, constipation, etc.
  • High levels of Vitamin D can also cause damage to the kidneys.


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