What is Vitamin D, D2, and D3?

By Canada Cloud Pharmacy | Published Thursday 08 October 2020

Vitamin D is a micronutrient and is essential for a healthy life. Vitamin D is a fat-soluble steroid hormone and the prime biological regulators of calcium homeostasis. 

Vitamin D exists in two forms:

  • Vitamin D2 (aka: ergocalciferol) - derived from plants, fungi, and yeasts.
  • Vitamin D3 (aka cholecalciferol) - found in skin, generated from provitamin D, 7- dehydrocholesterol by the action of sunlight or artificial ultraviolet light.

In humans, the potency of vitamin D2 is the same as that of D3, and therefore, vitamin D2 can also be used as a dietary substitute for vitamin D3. Vitamin D2 and D3 are metabolized in the liver, with the help of enzyme, 25-hydroxylase and 25-hydroxyvitamin D (25OHD) is formed. In the kidney, under the influence of parathyroid hormone, enzyme 1-alpha hydroxylase causes the conversion of 25OHD to 1,25-dihydroxyvitamin D; Calcitriol. Calcitriol is the pharmacologically active form of vitamin D.

What are the dietary sources of vitamin D?

Common foods that are good sources of vitamin D are:

  • Fatty fish (ex: herring, salmon sardines, pilchards)
  • Eggs
  • Vitamin D fortified dairy products such as milk, cheese, yogurt, skimmed milk powder, evaporated milk powder.
  • Food items commonly enriched with vitamin D are breakfast cereals, soup powders, and baby products.
  • Multivitamins supplement
    • Osto-D2 contains 50,000 IU of Vitamin D2.
    • Vitamin D3 is also given in combination with other drugs like Alendronate in the treatment of osteoporosis e.g.Fosavance

What are the symptoms of vitamin D deficiency?

Almost half of the Western elderly  population and nearly two-thirds of the rest of the world are deficient in Vitamin D and hence do not have healthy bones. Vitamin D deficieny in children is called Rickets and can cause the child to not be able to stand because of bone deformity in the lower limbs. Vitamin D deficiency in adults causes defective mineralization resulting in Osteomalacia. In both the conditions, patients suffer from pain, and muscle weakness in the limbs, heart, and respiratory systems. Vitamin D deficiency also increases the risk of other diseases, like osteoporosis, heart diseases, diabetes, cancer, and infectious diseases such as tuberculosis.

What is the Dietary Reference Value (DRV) for vitamin D?

Vitamin D intake varies from country-to-country depending on dietary habits, the use of dietary supplements, and the extent to which the national food supply is fortified with vitamin D. 
For the people residing in countries having restricted skin exposure to the sun-light of the necessary wavelengths, dietary supply of vitamin D is essential. 
For people with >50 years of age, Health Canada recommends a daily vitamin D supplement of 400 International Units (IU) (equivalent to 10 micrograms).


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