Vitamin D plays a critical role in bone health, immune function, and overall wellness. The two main forms—vitamin D2 and vitamin D3—share similar functions but differ in how they are sourced, absorbed, and used by the body.

Understanding these differences can help you choose the most effective option for maintaining healthy vitamin D levels.

What Vitamins D2 and D3 Do

Support Bone Health
Both vitamin D2 and D3 help your body absorb calcium and phosphorus, which are essential minerals for strong bones and teeth. Without enough vitamin D, bones may become thin, brittle, or soft, increasing the risk of fractures and osteoporosis. In children, severe deficiency can lead to rickets, a condition that causes bone deformities and delayed growth.

Support Immune And Muscle Function
Vitamin D also supports immune health, muscle strength, and proper nervous system function. Adequate levels help your body respond effectively to infections and maintain normal muscle movement and balance.

Vitamin D2 vs. Vitamin D3

Where They Come From
Vitamin D2 (ergocalciferol) is derived from plant and fungal sources. It forms when compounds in plants and fungi are exposed to ultraviolet (UV) light.

Vitamin D3 (cholecalciferol) is naturally produced in the skin when it’s exposed to sunlight. It’s also found in animal-based foods such as fatty fish, egg yolks, and dairy products.

How They’re Processed In The Body
Both vitamin D2 and D3 are absorbed in the small intestine and then converted by the liver into forms the body can use.

Vitamin D2 becomes 25-hydroxyvitamin D2, while vitamin D3 becomes 25-hydroxyvitamin D3. These forms are collectively known as calcidiol, which is what doctors measure in blood tests to assess vitamin D status.

Calcidiol is then converted in the kidneys into calcitriol, the biologically active form of vitamin D that helps regulate calcium balance and other bodily functions.

Vitamin D3 May Be More Effective

Better Absorption And Retention
Research suggests vitamin D3 may raise and maintain blood vitamin D levels more effectively than vitamin D2. A large review of multiple studies found that people taking vitamin D3 experienced significantly higher blood levels than those taking vitamin D2.

Vitamin D3 also appears to stay active in the body longer, helping maintain adequate levels over time. However, individual responses can vary depending on age, genetics, body composition, and sun exposure.

Recommended Daily Intake

Daily Vitamin D Needs
Vitamin D intake recommendations include all dietary and supplemental sources:

  • Infants (under 12 months): 400 IU (10 mcg)

  • Children 1–13 years: 600 IU (15 mcg)

  • Teens 14–18 years: 600 IU (15 mcg)

  • Adults 19–70 years: 600 IU (15 mcg)

  • Adults over 70: 800 IU (20 mcg)

  • Pregnant and breastfeeding individuals: 600 IU (15 mcg)

How To Increase Your Vitamin D Intake

Sunlight, Food, And Supplements
Vitamin D deficiency is relatively common, affecting an estimated 10% of people in the U.S. Sun exposure helps the body produce vitamin D naturally, but lifestyle, geography, sunscreen use, and skin tone can limit production.

You can increase your vitamin D intake by:

  • Spending short periods in sunlight safely

  • Eating vitamin D–rich foods

  • Taking supplements when needed

Vitamin D supplements are often the most reliable way to correct deficiency. Vitamin D3 supplements are commonly derived from lanolin (from sheep’s wool), while vegan-friendly versions may come from lichen.

Always speak with a healthcare provider before starting supplementation to determine the right dose for your needs.

Good Sources of Vitamin D2

Plant-Based Options
Vitamin D2 is primarily found in mushrooms, especially varieties exposed to UV light such as shiitake, maitake, and portobello mushrooms.

Other fortified sources include:

  • Fortified plant-based milk and dairy milk

  • Fortified breakfast cereals

  • Fortified orange juice

  • Vitamin D2 supplements

Good Sources of Vitamin D3

Animal-Based And Sun-Derived Sources
Vitamin D3 is mainly obtained through sun exposure and animal foods, including:

  • Cod liver oil

  • Fatty fish such as salmon and trout

  • Egg yolks

  • Beef liver

  • Canned tuna

  • Vitamin D3 supplements

Vitamin D3 is generally considered the most effective form for raising blood vitamin D levels.