Vitamin D deficiency: Symptoms, treatments & preferred foods

[Article updated on 19/09/2023]

Rickets, osteomalacia, muscle weakness, cardiovascular disease, autoimmune diseases, etc. are the consequences of a vitamin D deficiency. Each nutrient is essential, vitamin D is no less. It occupies an important place among the elements that make the body function. In this article, I will help you discover a little more about this very common deficiency which affects more than a billion people worldwide.

Before reading on

I’m not an expert in this field, but I am passionate about nutrition and health.

The articles you’ll find on my site are the result of in-depth research that I’d like to share with you. However, I would like to stress that I am not a health professional and that my advice should in no way replace that of a qualified physician. I’m here to guide you, but it’s important that you consult a professional for specific questions or medical concerns. Your well-being is important. So be sure to consult the appropriate experts and take the best possible care of yourself.

What is vitamin D deficiency?

Vitamin D deficiency or hypovitaminosis D results in having a concentration of 1,25-hydroxyvitamin-D lower than 20 nanogram per milliliter (ng/mL) in the blood. Vitamin D also known as the sunshine vitamin is a unique nutrient. First, it acts like hormones. Second, it is produced by the body itself thanks to exposure of the skin to the sun.

Everything you need to know about hypervitaminosis D.
Vitamin D also known as the sunshine vitamin is a unique nutrient.

Once landed in the body, it must still be converted into its active form called 1,25-hydroxyvitamin-D also called calcitriol to be operational. Vitamin D has two main functions:

  • It helps the body in the absorption of calcium and phosphorus
  • It controls the secretion of parathyroid hormone, a hormone responsible for bone resorption.

Thanks to these two functions, vitamin D maintains normal levels of calcium and phosphorus in the blood, and thus ensures bone health. It monitors the condition of the muscles and improves the immune system. It also prevents certain cancers and diabetes and many others.

What are the causes of vitamin D deficiency?

Hypovitaminosis D can occur for various reasons: medical reasons, geographical location, diet, hygiene and lifestyle, etc.

Diet low in vitamin D

Unlike other nutrients, foods rich in vitamin D are few in number. People following a restricted diet such as vegetarians or those allergic to foods containing vitamin D have a high chance of being deficient in vitamin D. The same goes for infants who feed only on breast milk, vitamin D being almost non-existent in this one.

Limited sun exposure

Ultraviolet B from the sun is the main element in the production of vitamin D by the body. People who are indoors too often, always sheltered from the sun, those who always wear sunscreen or those who cover themselves from head to toe are at risk of hypervitaminosis D.

Everything you need to know about hypervitaminosis D.
Ultraviolet B from the sun is the main element in the production of vitamin.

But other people are also at risk, those with limited access to the sun because of their geographic location or the season.

Inability of the body to absorb vitamin D

Nutrients are absorbed by the small intestine. But certain diseases such as celiac disease, cystic fibrosis, Crohn’s disease prevent the intestine from functioning properly and thus absorbing nutrients. Certain surgeries also, notably obesity surgery such as gastric bypass, reduce the quantity of nutrients that can be consumed and can lead to a deficiency.

Skin color

Studies have shown that dark skin does not synthesize as much vitamin D as light skin. This is because of the higher level of melanin in dark skin. The darker the shade, the more melanin there is and the less vitamin D it produces. As a result, people with dark skin must expose themselves to the sun longer than those with light skin.


Taking certain medications can lower the level of vitamin D in the blood. Here are some examples:

  • Laxatives
  • Steroids: prednisone
  • Cholesterol-lowering medications: cholestyramine, colestipol
  • Antiepileptic drugs: phenobarbital, phenytoin
  • Drugs for tuberculosis: rifampicin
  • Medications for weight loss: orlistat

Inability of the body to convert vitamin D into its active form

The liver and kidneys are responsible for converting vitamin D into its active form by producing the corresponding enzymes. So, if they are damaged due to disease, then vitamin D cannot be converted.

Everything you need to know about hypervitaminosis D.
The liver and kidneys are responsible for converting vitamin D.

And without being in its active form, vitamin D cannot do its job.

Obesity and overweight

In the case of the chronic disease of obesity, vitamin D is stuck in fat cells preventing them from acting on the body. Obesity is often linked to a vitamin D deficiency. All people with a body mass index greater than 30 kg/m2 are certainly at risk of being deficient in vitamin D.


The body’s ability to produce vitamin D decreases with age. This is due to the decrease in kidney function. As a result, the body will also have difficulty absorbing calcium and phosphorus.

What are the symptoms of vitamin D deficiency?

Hypovitaminosis D may have no symptoms. The signs may vary depending on the degree of the deficiency. It can cause rickets in children or osteomalacia in adults when the deficiency is very severe. Apart from this, people suffering from a vitamin D deficiency may experience the following symptoms:

  • Tiredness
  • Bone pain
  • Pain, weakness and muscle cramp
  • Weight gain
  • Depression and anxiety
  • Slow healing after injury, surgery or infection
  • Gets sick often
  • Hair loss

What to do in case of vitamin D deficiency?

If you think you are deficient in vitamin D, consult your doctor right away so that you can follow the appropriate treatment. He will guide you and prescribe vitamin supplements if necessary. Self-medication is strongly discouraged.

Everything you need to know about hypervitaminosis D.
Consult your doctor right away.

The only thing you can do in the meantime is eat foods rich in vitamin D and get out in the sun. However, the advice of a doctor will always be necessary even when it comes to sunbathing.

How to diagnose a vitamin D deficiency?

Blood testing is the only way to ensure whether an individual is deficient in vitamin D or not. For hypovitaminosis D, the test consists of analyzing the serum level of 25-hydroxyvitamin-D in the blood. The normal level of calcitriol in the blood is greater than or equal to 20 ng/mL. If the value is between 12 to 20 ng/mL, the diagnosis is vitamin D insufficiency. The doctor confirms a vitamin D deficiency when the calcitriol level is less than 12ng/mL.

Treatments for vitamin D deficiency

Everything you need to know about hypervitaminosis D.
Blood tests may take place throughout treatment.

The treatment mainly consists of taking vitamin D supplements. Vitamin D supplements exist in 2 formats: vitamin D2 called ergocalciferol, it is of plant origin and vitamin D3 called cholecalciferol of animal origin. The dosage and duration of treatment varies depending on the stage of the deficiency and the patient’s situation. For example, for an individual with no nutrient absorption problems, the dosage is approximately 1250 microgram (mcg) once or twice a week, for 6 to 8 weeks and then reduce the dose to 20 to 25 mcg. The supplement exists in several formats: tablets, liquids, powders, etc. it can even be done by injection. Taking calcium in parallel with the vitamin D supplement is also recommended. Apart from this, the doctor will also recommend consuming foods rich in vitamin D and going outside from time to time so that the skin can come into contact with the sun’s rays. Blood tests may take place throughout treatment to adjust the dosage of supplements in accordance with the level of calcitriol in the blood.

Foods to choose to limit the risk of vitamin D deficiency

Foods rich in vitamin D are mainly foods of animal origin:

  • Oily fish: mackerel, sardines, salmon, trout, tuna, herring
  • Liver of beef
  • Egg yolk
  • Cheese (Emmental)
  • Soy milk
  • Mushroom

Foods fortified with vitamin D: cereals, orange juice, cow’s milk, margarine, etc.