Vitamin D is a crucial fat-soluble vitamin that plays many roles in maintaining health—from supporting bone density to boosting immune defense and brain performance. But when it comes to supplements or food fortification, you’ll often see two versions: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Although both types help the body raise vitamin D levels, they differ in origin, absorption, and potency.

What Vitamin D2 and D3 Do in the Body

Both D2 and D3 help the body absorb calcium and phosphorus—two essential minerals for strong bones and teeth. Inadequate levels of vitamin D can lead to brittle bones, fractures, and in severe cases, rickets in children or osteoporosis in adults.

Beyond bone health, vitamin D influences immune regulation, muscle function, and the nervous system’s communication pathways.

How They Differ

Sources

  • Vitamin D2 is found in plant-based sources, particularly UV-exposed mushrooms and fortified foods like plant-based milk or cereals.

  • Vitamin D3 is synthesized in the skin when exposed to sunlight and is also found in animal-based foods such as fatty fish, liver, eggs, and dairy.

Metabolism

Both forms are absorbed in the intestine and processed by the liver into 25-hydroxyvitamin D (calcidiol), the main form measured in blood tests. However, vitamin D3 has been shown to be more effective at raising and maintaining these levels over time.

Stability and Potency

Studies suggest that vitamin D3 is more stable and bioavailable, meaning it stays in the body longer and is better at sustaining adequate vitamin D levels. For this reason, D3 is often the preferred form in supplements.

Recommended Daily Intake

The daily requirements for vitamin D vary based on age and health status:

  • Infants (0-12 months): 400 IU

  • Children and teens: 600 IU

  • Adults under 70: 600 IU

  • Adults 71 and older: 800 IU

  • Pregnant/breastfeeding: 600 IU

These amounts cover both dietary and supplemental sources and are usually not specific to D2 or D3. However, due to its effectiveness, vitamin D3 is more commonly used in meeting these recommendations.

How to Increase Your Vitamin D Levels

1. Sunlight Exposure

Just 10–30 minutes of midday sun several times a week can trigger D3 production. However, factors like skin tone, geographic location, and sunscreen use can affect synthesis.

2. Diet

Rich Sources of D2:

  • UV-exposed mushrooms

  • Fortified plant-based milks and cereals

  • Fortified orange juice

Rich Sources of D3:

  • Cod liver oil

  • Salmon, trout, tuna

  • Egg yolks

  • Beef liver

  • Fortified dairy products

3. Supplements

Vitamin D supplements are widely available in both D2 and D3 forms. If you're vegan or plant-based, choose D2 or vegan D3 derived from lichen. Otherwise, D3 from lanolin is typically more effective.

A Quick Summary

Vitamin D2 and D3 are both beneficial for raising vitamin D levels, but D3 is often more effective and longer-lasting. While D2 comes from plant-based sources, D3 is produced through sunlight exposure and animal-based foods.

For most people, D3 is the preferred supplement form—unless dietary restrictions require otherwise. If you're unsure about your vitamin D needs, speak with a healthcare provider to evaluate your levels and choose the right strategy.