What is the other name for vitamin D?

December 30, 2025 •

3 min read

According to the National Institutes of Health, vitamin D is a fat-soluble vitamin found naturally in a few foods, added to others, and available as a dietary supplement. The broader chemical term for vitamin D, encompassing its various forms, is calciferol.

Quick Summary

The term calciferol is the collective name for the family of compounds known as vitamin D. It includes two primary forms: ergocalciferol (vitamin D2), found in plants, and cholecalciferol (vitamin D3), produced by the body upon sun exposure and found in animal-based foods. This nutrient is vital for bone health, calcium absorption, and immune function.

Key Points

Calciferol is the other name: The term 'calciferol' is the scientific name for the group of compounds known as vitamin D.
Two main types exist: The two most important forms are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).
D3 from sun and animals: The body produces vitamin D3 upon exposure to sunlight and it is also found in animal-based foods.
D2 from plants and fungi: Vitamin D2 is derived from plant sources, such as UV-exposed mushrooms and fortified plant milks.
Activation is required: Both forms are inactive and must be converted by the liver and kidneys into calcitriol, the active hormone.
Role in calcium absorption: Calciferol's primary function is to promote the absorption of calcium for strong bones and teeth.
Crucial for immune function: It also plays a vital role in modulating the immune system and reducing inflammation.
Deficiency leads to health issues: A deficiency can result in conditions like rickets in children and osteomalacia in adults.

Calciferol: The Chemical Family of Vitamin D

While most people know it simply as vitamin D, the more precise chemical name for this essential nutrient is calciferol. This name actually refers to a group of fat-soluble secosteroids responsible for increasing the intestinal absorption of calcium, phosphate, and magnesium. The term calciferol is a blanket designation for several related compounds, with the two most significant forms for human health being vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both forms, whether from sunlight, food, or supplements, are biologically inactive until they are metabolized by the body into their active hormonal form, calcitriol.

The Two Primary Forms: D2 and D3

Vitamin D2 (Ergocalciferol)

Vitamin D2, or ergocalciferol, is primarily found in plant sources, including certain fungi and fortified foods. It is produced by the ultraviolet irradiation of ergosterol in yeast. Vegans and vegetarians often rely on D2-fortified foods and supplements to meet their vitamin D needs. Sources include UV-exposed mushrooms, fortified cereals, and plant-based milks.

Vitamin D3 (Cholecalciferol)

Vitamin D3, or cholecalciferol, is considered the more potent form of the vitamin. The human body synthesizes it when the skin is exposed to ultraviolet B (UVB) light from the sun. It is also found naturally in animal-based foods such as fatty fish, egg yolks, beef liver, and cheese. Some studies suggest that D3 may be more effective at raising and maintaining vitamin D levels in the blood than D2.

Synthesis and Activation: The Body's Process

Regardless of whether it is D2 or D3, all forms of vitamin D must be activated by the body before they can be used effectively. This process involves two hydroxylation steps:

First Hydroxylation: Occurs in the liver, where vitamin D is converted into 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. This is the major circulating form of vitamin D in the body and is what is typically measured in a blood test to assess a person's vitamin D status.
Second Hydroxylation: Takes place primarily in the kidneys, where calcidiol is converted into the biologically active hormone, 1,25-dihydroxyvitamin D [1,25(OH)2D], which is also called calcitriol. Calcitriol is the form that plays the crucial role in promoting calcium absorption and regulating bone health.

Key Roles of Calciferol in the Body

Supporting Bone Health

Calciferol is fundamentally essential for bone health. Its most well-known function is promoting the absorption of calcium from the gut. Without sufficient vitamin D, the body cannot absorb calcium effectively, which can lead to bones becoming thin, brittle, or misshapen. In children, this can cause rickets, while in adults, it can lead to osteomalacia or contribute to osteoporosis.

Modulating Immune Function

Beyond bone health, calciferol plays a significant role in modulating the immune system. Vitamin D receptors are found on various immune cells, and research has shown that adequate vitamin D levels are important for proper immune function. It helps to regulate immune responses and may help protect against certain infections.

Comparison Table: Vitamin D2 vs. Vitamin D3


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Primary Source	Plants and fungi (e.g., UV-exposed mushrooms)	Animal products (e.g., fatty fish, eggs) and sunlight exposure
Common Availability	Found in fortified foods like cereals and some plant-based milks	Found in animal-derived foods and produced naturally by the body
Typical Supplementation	Available in supplements, often lower cost	Available in supplements, generally considered more effective
Chemical Structure	Contains a double bond and extra methyl group in its side chain	Possesses a single bond in its side chain structure
Effectiveness	Considered effective for treating deficiency, but some studies suggest lower potency than D3	May be more effective at raising and sustaining blood vitamin D levels
Vegan-Friendly	Sourced from plants, making it a suitable vegan option	Often animal-derived, though some vegan D3 from lichen is available

Conclusion

In conclusion, the general term for vitamin D is calciferol, which includes the two primary forms, ergocalciferol (D2) and cholecalciferol (D3). While they serve the same function of regulating calcium and promoting bone and immune health, they differ in their origin and, in some respects, their potency. For most individuals, the distinctions are minor, but those with specific dietary requirements or severe deficiencies may need to consider the source. Understanding the different names and forms of this essential nutrient is key to maintaining adequate levels for overall health. As always, consulting with a healthcare provider can help determine the best source and dosage for individual needs. For more authoritative health information, visit the National Institutes of Health (NIH).

Frequently Asked Questions

Vitamin D is called calciferol because this is the broader chemical term for the family of compounds that constitutes vitamin D. The name comes from its role in calcium (calc-) absorption and its chemical structure (-ferol).

The main difference is their source and molecular structure. D2 comes from plants and fungi, while D3 is produced in the skin upon sun exposure and found in animal products. Some research suggests D3 may be more effective at raising blood levels.

Calcitriol is the biologically active hormonal form of vitamin D. It is produced primarily in the kidneys after vitamin D from sun or diet is first processed by the liver.

Yes, both can be taken together as they serve the same function in the body. However, taking excessively high doses of any form of vitamin D can be harmful. It is best to consult a healthcare provider for the right dosage.

Common sources include sunlight exposure, fatty fish (like salmon and tuna), fortified dairy and plant-based milks, egg yolks, and mushrooms exposed to UV light.

Vitamin D is essential for regulating calcium and phosphate levels in the blood. It promotes their absorption from the gut, which is crucial for the mineralization and health of bones.

A deficiency can lead to various health problems. In children, it causes rickets, while in adults, it can cause osteomalacia, both involving soft or weakened bones. It can also impact immune function.