Vitamin D vs D3

Last Updated: April 28, 2024

Vitamin D vs D3

Vitamin D is essential for maintaining healthy bones and supporting the immune system, among other vital roles in the human body. However, there’s often confusion between Vitamin D and its specific form, Vitamin D3. This article elucidates the differences between the two, ensuring clarity on how they contribute to our health.

What is the difference between Vitamin D and D3?

VVitamin D is a crucial nutrient that plays a pivotal role in bone health and immune function, among other things. It comes in several forms, but the most significant for humans are Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Vitamin D2 is derived from plant sources and fortified foods, whereas Vitamin D3 is synthesized by the human skin when exposed to sunlight and is also found in animal products. Of the two, Vitamin D3 is noted for being more effective in raising and maintaining vitamin D levels in the blood, making it crucial for bone health, immune support, and overall well-being.

Vitamin D

Vitamin D, often referred to as the “sunshine vitamin,” is unique because it can be synthesized by the body when exposed to sunlight. It is fat-soluble and exists in two main forms:

  • Vitamin D2 (Ergocalciferol): Primarily obtained from plant sources and certain fungi.
  • Vitamin D3 (Cholecalciferol): Found in animal products and synthesized by the skin upon sun exposure.

Key Characteristics of Vitamin D

  • Source: Obtained from plant sources such as mushrooms, as well as fortified foods like cereals and some types of milk.
  • Bioavailability: Less efficient in raising blood levels of 25-hydroxyvitamin D compared to D3.
  • Conversion: Metabolized in the liver to 25-hydroxyvitamin D2, a precursor to the active form of vitamin D in the body.
  • Potency: Generally considered less potent and has a shorter duration of action in the body compared to D3.

Vitamin D3

Vitamin D3, specifically, is considered more potent and effective at raising and maintaining overall Vitamin D levels in the body compared to D2. It is naturally produced by the skin when exposed to sunlight and can also be obtained through dietary sources like fatty fish, liver, and egg yolks, as well as through supplements.

Key Characteristics of Vitamin D3

  • Source: Synthesized by the body through skin exposure to sunlight; also found in animal-based foods.
  • Bioavailability: More effective in raising and maintaining blood levels of 25-hydroxyvitamin D.
  • Conversion: Metabolized in the liver to 25-hydroxyvitamin D3, and subsequently to its active form in the kidneys.
  • Potency: Higher potency and longer duration in the body compared to D2.

Differences Between Vitamin D and D3

AspectVitamin D (General)Vitamin D3 (Cholecalciferol)
SourceVitamin D is obtained in two main forms: D2 from plants and fortified foods, and D3 from animal sources and sunlight.D3 is sourced from animal products and synthesized by the skin upon exposure to sunlight.
OriginsD2 is derived from fungal and plant sources, while D3 is produced in the skin through sun exposure and found in animal-based foods.D3 originates from the skin’s reaction to UVB sunlight and is present in fatty fish, liver, and egg yolks.
Potency and EfficacyD2 is considered less potent and effective in raising vitamin D levels in the bloodstream.D3 is more potent, raising and maintaining vitamin D levels more efficiently.
Absorption and ConversionThe body might not absorb and convert D2 to its active form as efficiently as D3.D3 is absorbed and converted into its active form in the body more effectively.
StabilityD2 can be less stable, degrading more easily when exposed to varying temperatures and humidity.D3 tends to be more stable, making it more reliable in supplements and fortified foods.
Impact on Vitamin D ReceptorsD2 and D3 may bind differently to vitamin D receptors, potentially affecting the genomic and non-genomic actions of vitamin D.D3 binds more effectively to receptors, potentially offering greater health benefits.
Supplementation PreferencesD2 is often used in supplements for those with dietary restrictions (e.g., vegans), as it is plant-based.D3 supplements are often recommended for their higher potency and efficiency, especially in older adults and those with limited sun exposure.
Metabolic PathwaysOnce ingested or synthesized, D2 follows a specific pathway in the liver to be metabolized into its active form.D3 undergoes metabolism in the liver and kidneys, converting into the biologically active form of vitamin D more readily.
Role in HealthBoth forms are crucial for calcium absorption, bone health, and muscle function, but their efficacy can differ.D3 not only supports bone health but also plays a significant role in immune function, cell growth, and inflammation reduction.

Key Similarities Between Vitamin D and D3

Biological Significance

Both Vitamin D and Vitamin D3 are essential for the regulation of calcium and phosphate in the body. This is crucial for maintaining healthy bones and teeth. They support the absorption of calcium in the intestines, which is vital for the normal mineralization of bone.

Source and Synthesis

Vitamin D can be synthesized by the body upon exposure to sunlight, specifically UVB rays. Vitamin D3, also known as cholecalciferol, is the form of Vitamin D that is produced in the skin in response to sunlight exposure. Additionally, both can be obtained from dietary sources, although Vitamin D3 is commonly found in animal-based foods like fatty fish, liver, and egg yolks.

Immune Function

Both Vitamin D and D3 contribute to the immune system’s functionality. They play a role in modulating the immune response, helping the body to fend off pathogens while ensuring that the immune system does not overreact in a way that can lead to autoimmunity.

Deficiency Concerns

A deficiency in either Vitamin D or specifically in D3 can lead to similar health issues, including rickets in children (a condition characterized by soft and weakened bones), and osteomalacia or osteoporosis in adults, conditions that involve the softening of bones or reduction in bone density, respectively.


In dietary supplements, Vitamin D is often provided as Vitamin D3 because it is more effective at raising and maintaining adequate levels of Vitamin D in the blood compared to other forms. When people talk about Vitamin D supplements, they are usually referring to D3.

Metabolic Pathway

Once ingested or synthesized in the skin, both Vitamin D and D3 undergo two hydroxylation reactions in the body: first in the liver to become 25-hydroxyvitamin D [25(OH)D], and then in the kidney to become the biologically active form, 1,25-dihydroxyvitamin D. This pathway highlights their interrelated roles in the body’s metabolism of Vitamin D.

Key Differences Between Vitamin D and D3

  • Source: The primary distinction lies in their sources. Vitamin D3 comes from animal sources and sun exposure, whereas Vitamin D2 is plant-based.
  • Potency: Research suggests that Vitamin D3 is more effective in raising the body’s Vitamin D levels compared to D2. This is due to its greater affinity for Vitamin D binding proteins in the plasma, leading to better utilization by the body.
  • Function: Both forms function similarly in the body once converted into the active form of Vitamin D, known as calcitriol. However, due to the higher potency and longer shelf-life of D3, it is often preferred for fortification and supplements.
  • Metabolism: Once ingested or synthesized, both forms of Vitamin D undergo similar metabolic processes in the liver, where they are converted into calcifediol, the storage form of vitamin D. However, Vitamin D3’s conversion rate and subsequent increase in blood levels of calcifediol are generally higher compared to Vitamin D2, making D3 more potent.
  • Usage and Supplementation: Given its higher potency and the body’s ability to synthesize it through sunlight exposure, Vitamin D3 is often the preferred form in dietary supplements and therapeutic applications.


Is it better to take vitamin D or D3?

Vitamin D3 is often preferred due to its superior ability to maintain and raise blood vitamin D levels effectively.

Is vitamin D3 the same as just vitamin D?

Vitamin D3 is a specific form of Vitamin D, more potent and effective than its counterpart, Vitamin D2.

Why do doctors prescribe vitamin D instead of D3?

Doctors may prescribe generic “vitamin D” to encompass both D2 and D3 forms, depending on dietary sources and individual needs.

Is eating vitamin D and D3 the same thing?

Eating vitamin D typically refers to both D2 and D3 intake, with D3 being more efficiently utilized by the body.

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