Vitamin D on a vegan diet: sunlight, D2, and lichen-derived D3
Nothing about being vegan makes vitamin D harder except that fortified dairy and oily fish are off the table — and neither was ever a large contributor. In the UK, the NHS advises everyone to consider a supplement from October to March. Treat this as a general population issue you happen to be reading about on a plant-based site.
Key facts
- Daily target used here
- 800 IU
- Food sources listed
- 7
- Richest source
- Midday summer sun on arms and legs — 10000 IU
- Supplement
- D2 or vegan D3?
How much you need
NHS 400 IU; many clinicians use 1,000 IU
Melanin slows cutaneous synthesis
NHS and equivalent guidance
Do not self-prescribe high doses
IOM tolerable upper intake level
Where it comes from
| Food | Serving | IU | % of target |
|---|---|---|---|
| Midday summer sun on arms and legsHighly variable by latitude, season, skin tone and age | 10–30 minutes | 10000 | 1250% |
| Lichen-derived D3 supplement | 1 capsule | 1000 | 125% |
| D2 (ergocalciferol) supplementEffective but shorter-acting than D3 | 1 capsule | 1000 | 125% |
| UV-exposed mushroomsOnly if labelled 'grown in UV light' or sun-dried | 100 g | 400 | 50% |
| Fortified plant milk | 250 ml | 100 | 13% |
| Fortified breakfast cereal | 40 g | 40 | 5% |
| Fortified vegan spread | 10 g | 30 | 4% |
Getting it absorbed, not just eaten
Take it with fat
Vitamin D is fat-soluble. Swallowing a capsule with the largest meal of the day measurably improves absorption compared with taking it on an empty stomach.
Latitude and season set the ceiling
Above roughly 37° north or south, the sun's angle from about October to March is too low for the skin to make any vitamin D, no matter how long you stand outside.
Magnesium is a cofactor
Activating vitamin D requires magnesium-dependent enzymes. A diet with plenty of legumes, nuts, seeds and whole grains supplies it — one more reason food and supplements work together.
D2 or vegan D3?
Both are vegan (D3 from lichen; the conventional version comes from sheep's wool lanolin). Head-to-head trials show D3 raises and holds serum 25(OH)D more effectively, especially with weekly dosing. Look for 'vegan D3' or 'cholecalciferol from lichen' certified by a vegan trademark, since most D3 on the shelf is not vegan.
Signs of running low
- Persistent tiredness and low mood, often worse in winter
- Bone and lower back pain, muscle aches and weakness
- Frequent infections
- In children, rickets — bowed legs and delayed growth
- In adults, osteomalacia — soft, painful bones
What to test
- Serum 25(OH)D
- The standard test. Under 25–30 nmol/L is deficient; many clinicians aim for 50–75 nmol/L.
- Test in late winter
- February or March gives the year's low point and the most useful reading.
- Retest after 3 months of supplementing
- Individual response varies widely with body weight and genetics.
Common mistakes
Assuming sunscreen makes supplementation pointless
Real-world sunscreen use reduces synthesis less than lab studies suggest, but it does not replace winter supplementation either way. Keep the sunscreen; take the capsule.
Buying D3 without checking the source
Standard D3 is extracted from lanolin. Only lichen-derived D3 is vegan.
Mega-dosing
Very high doses do not improve outcomes and can cause hypercalcaemia. Stay under 4,000 IU/day without medical supervision.
Questions people ask
Is vitamin D2 enough for vegans?
It works, and it is what many fortified foods use. D3 from lichen maintains blood levels more consistently, so it is the better first choice if available.
Can mushrooms supply vitamin D?
Only UV-exposed ones. Mushrooms grown in the dark contain almost none; UV-treated or sun-dried mushrooms can supply several hundred IU per 100 g.
How much sun do I need?
In summer, roughly 10–30 minutes of midday sun on forearms and legs several times a week for lighter skin, considerably longer for darker skin. In winter above 37° latitude, no amount is sufficient.
Should I take vitamin D with K2?
Some practitioners recommend it to direct calcium into bone. Evidence is suggestive rather than conclusive; vegan K2 comes from natto or fermented chickpea sources.
Is deficiency more common in vegans?
Cohorts show slightly lower average levels, but deficiency is widespread in the general population too. Latitude, skin tone and time indoors matter more than diet.
References
Other nutrient guides
Reviewed 2026-08-23 by the Veg.ac editorial team · Data: NIH ODS — Vitamin D fact sheet · Free to reuse under CC BY 4.0 with a link back.
General information, not medical advice. Talk to a clinician or registered dietitian about your own situation.