Vitamin D: Health Benefits, Dosing & Normal Levels

Updated in February 2023

Vitamin D is a hormone that regulates calcium and phosphorus concentration in the bones. It also boosts the immune system and can prevent chronic diseases, like diabetes and high blood pressure. 

Vitamin D is produced by the body in the form of vitamin D3 (also known as cholecalciferol) when the skin is exposed to sunlight. It can also be obtained through animal food sources, like fish and milk. Its vitamin D2 form (ergocalciferol) is present in supplements, fortified food, and some vegetables and fungi. 

A vitamin D deficiency can cause bone abnormalities, like osteomalacia or osteoporosis in adults, or rickets in children. It is also believed that a vitamin D deficiency may increase your risk for developing diabetes, high blood pressures, colds and flus. 

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Health benefits

Vitamin D is used for the following functions in the body: 

  • Strengthening the bones and teeth, as it can increase calcium and phosphorus absorption in the intestines and facilitate the use of these minerals for bone formation 
  • Preventing diabetes, because it promotes pancreatic health, which is essential for insulin production and glucose regulation 
  • Improving the immune system and preventing the cold or flu 
  • Reducing systemic inflammation, which can prevent and treat autoimmune diseases like psoriasis, rheumatoid arthritis, inflammatory bowel syndrome and lupus 
  • Improving cardiovascular health, by preventing illnesses like hypertension, heart attacks, heart failure and atherosclerosis
  • Boosting muscular strength, as Vitamin D is required for muscle growth and promotes strength, which can prevent falls in older adults 

Vitamin D is also needed for the production of keratinocytes, which are cells that are responsible for maintain skin hydration and smoothness. 

As you can see, vitamin D is necessary for many different processes in the body. Therefore, it is important that you have adequate levels circulating in the blood. 

Difference between vitamin D2 and D3

Vitamin D3 is produced by the body when the skin is exposed to sunlight. This vitamin is also found in animal food sources, like egg yolks, yogurt and milk, as well as supplements. It is believed that this form remains better balanced and at adequate levels in the blood.

Vitamin D2 can also be produced through sun exposure, although it is only found in some vegetables and fungi (like mushrooms and yeast). This type of vitamin can also be found in supplements and fortified foods, like milk and cereal. 

Vitamin D foods

The main source of vitamin D is through its production in the skin, which is triggered by exposure to sunlight. Therefore, it is important for people with lighter skin to absorb sunlight at least 15 minutes per day, and people with tan or darker skin to absorb at least 30 minutes of sun today. 

Ideally, you should exposure yourself to the sun on a daily basis with your arms and legs exposed. Try sitting in the sun before 10 am or after 3 pm without sunscreen. However, if you do sit in the sun between 10 am and 4pm, you should use sunscreen. 

In addition to sun exposure, vitamin D can also be obtained through certain foods, such as: 

  • Fish liver oil
  • Salmon
  • Seafood
  • Butter
  • Egg yolks
  • Milk and dairy products 

It is important that these foods are part of a healthy and balanced diet that also incorporates daily sun exposure. Read more about different food sources of vitamin D that you can consume. 

Recommended dose

The daily recommended daily dose for vitamin D varies depending on age and life stage: 

Life stage

Recommended daily daily dose

0 to 12 months 

10 mcg

1 to 70 years old

15 mcg

Over 70 years old 

20 mcg

When pregnant or breastfeeding

15 mcg

Solely consuming vitamin D foods is not sufficient to obtain the necessary daily dose of this vitamin, which is why exposure to sun is also important. In cases where daily sun exposure is not necessary (in cold countries for example), or if patients chronically have a problem with fat absorption, supplementing with vitamin D may be necessary. 

Normal levels

Vitamin D levels are considered to be normal when above 20 ng/mL, particularly for people over 60, pregnant or breastfeeding women, or for patients with kidney disease or intestinal absorption issues. 

How vitamin D levels are measured

Levels can be verified through a blood test, also known as the  25-hydroxy vitamin D test. It is possible to confirm, through this test, whether vitamin D levels in the blood are too high or too low D.

Vitamin D deficiency

A vitamin D deficiency can be caused by low ingestion of vitamin D foods or minimal sun exposure. It may also be noted in other conditions, like in people with vegetarian diets, patients who have undergone bariatric surgery, or patients with other chronic diseases, like kidney insufficiency or inflammatory bowel syndromes. 

Some signs and symptoms of a vitamin D deficiency include decreased calcium and phosphorus levels, muscular pain or weakness, bone weakness, osteoporosis in older adults, rickets in children and osteomalacia in adults. 

Read more about what causes vitamin D deficiency and how it is treated.

High vitamin D levels

High vitamin D levels generally occur with supplementation and can lead to weakening of the bones. It may also cause high calcium levels, which may increase the risk for kidney stones and cardiac arrhythmia.

The main symptoms of excess vitamin D include loss of appetite, nausea, vomiting, urinary frequency, weakness, high blood pressure, thirst, itchy skin and agitation.