Vitamin D supports bones, immunity, mood and muscle function — but the bottle you pick matters. D2 and D3 are not the same, and extras like K2 change what the supplement does. Here is a simple breakdown of the main types and what each one is best for.
| Type | Source | What it does | Best for |
|---|---|---|---|
| Vitamin D3 (cholecalciferol) | Sunlight, lanolin, oily fish | Raises blood vitamin D levels most effectively; supports bones, immunity and mood. | General deficiency and daily maintenance — the best-studied all-rounder. |
| Vitamin D2 (ergocalciferol) | UV-exposed mushrooms and yeast | Raises vitamin D levels but is less potent and shorter-lasting than D3. | People who specifically want a non-lanolin, fungal-source option. |
| Vitamin D3 + K2 | Combined supplement | D3 aids calcium absorption while K2 helps direct calcium to bones rather than soft tissues. | Bone and heart health together. |
| Vegan D3 (from lichen) | Lichen | Plant-based D3 with the same effectiveness as regular D3. | Vegans and vegetarians who want D3 potency without animal sources. |
| Calcifediol | Prescription only | A pre-converted form that raises blood levels faster than standard D3. | Severe deficiency, only under medical supervision. |
You will also see vitamin D as drops, capsules, softgels and sprays. The format matters less than the type and dose — drops and sprays can suit people who struggle with pills, and taking it with a meal containing some fat helps absorption.
Which one should you choose? For most people, D3 is the default — vegan D3 if you avoid animal products, and D3 + K2 if bone health is your focus. If you suspect a deficiency, ask your doctor for a blood test before supplementing at high doses.
This guide is for general information only and is not medical advice.