Vitamin D2 (Ergocalciferol)

Plant-derived form of vitamin D that's vegan-friendly but less potent than vitamin D3

Scientific nameErgocalciferol FormulaC28H44O Molecular weight396.65 g/mol CAS50-14-6

60 absorption score

8 safety / 10

15 USD per month

5 documented interactions

Check it against something

Evidence level A

Vitamin D2 (Ergocalciferol) with:

99 out of 100

Works better together Compatible. Timing differs, so follow each supplement's own window.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Bone health support

Supports calcium absorption and bone mineralization

Converted to calcitriol for calcium homeostasis Evidence A-grade 8-12 weeks

Immune system support

Enhances immune function and reduces infection risk

Modulates immune cell function via vitamin D receptors Evidence B-grade 4-8 weeks

Vegan-suitable option

Provides vitamin D without animal-derived ingredients

Plant-based source meets ethical dietary requirements Evidence A-grade Immediate ethical benefit

Deficiency prevention

Prevents vitamin D deficiency symptoms

Raises 25(OH)D blood levels, though less efficiently than D3 Evidence A-grade 4-8 weeks

Muscle function support

Maintains muscle strength and function

Vitamin D receptors in muscle tissue Evidence B-grade 8-12 weeks

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Probiotics for Autoimmune Disease Support Gut health & immune modulation 10-100 billion CFU daily B 60% Calcium Bone health & muscle function 1,000-1,200 mg A 30% Turmeric Anti-inflammatory & antioxidant 300-1000mg A 3% Vitamin D3 Bone health & immune support 1000-2000 IU A 85% Collagen Peptides Skin health & joint support 5-15g B 85% Calcium Carbonate Affordable bone health & antacid 1000-1200 mg A 25%

Or a different form of the same thing

the comparison people search most

Vitamin D2 (Ergocalciferol) vs Vitamin D3 absorption 60 against 85 · $15 against $8 a month 85%

All Vitamin D forms ranked by absorption →

Every pair we checked

12 combinations scored by the engine

Vitamin D2 (Ergocalciferol) + Vitamin D3 May compete with D3 for binding proteins Needs attention 68

Vitamin D2 (Ergocalciferol) + Caffeine No documented interaction either way No known interaction 70

Vitamin D2 (Ergocalciferol) + Creatine Monohydrate No documented interaction either way No known interaction 70

Vitamin D2 (Ergocalciferol) + Whey Protein No documented interaction either way No known interaction 70

Vitamin D2 (Ergocalciferol) + Turmeric No documented interaction either way No known interaction 70

Vitamin D2 (Ergocalciferol) + Vitamin C (Ascorbic Acid) May compete with D3 for binding proteins Needs attention 72

Vitamin D2 (Ergocalciferol) + Lactase Improved calcium absorption when consuming dairy Works better together 82

Vitamin D2 (Ergocalciferol) + Bovine Collagen Essential for collagen synthesis and cross-linking Works better together 82

Vitamin D2 (Ergocalciferol) + DHA Prevents oxidation of DHA and enhances stability Works better together 82

Vitamin D2 (Ergocalciferol) + Fish Oil (EPA/DHA) Protects fish oil from oxidation Works better together 90

Vitamin D2 (Ergocalciferol) + Magnesium Oxide Essential cofactor for vitamin D metabolism Works better together 94

Vitamin D2 (Ergocalciferol) + Calcium Carbonate High calcium may reduce D2 effectiveness Needs attention 94

Dosage

Morning with fat

Daily2000-4000 IU

Maintenance2000-3000 IU

Therapeutic4000-8000 IU

Maximum10000 IU

D3 equivalent1000 IU D2 ≈ 700 IU D3

Upper limit 100 mcg (4000 IU) NIH ODS

Before you take it

Pregnancygenerally safe at standard doses

VeganYes

When to expect it

First Effects2-4 weeks for blood level changes

Peak Benefits8-12 weeks for bone and immune benefits

Deficiency Development2-4 months without intake

Toxicity OnsetSeveral months of very high doses

How to measure it

$50-80

Marker25(OH)D (measures both D2 and D3)

Optimal40-60 ng/mL (100-150 nmol/L)

Deficient below20 ng/mL (50 nmol/L)

FrequencyEvery 3-6 months when supplementing with D2

What people actually reported to the FDA

CAERS, 276 reports naming it as the suspect

Most reported effects

Dyspnoea 25

Coeliac disease 14

Excluded from the list above: choking (76), dysphagia (38), foreign body trauma (22), foreign body (16). Those are people struggling with the tablet itself, not with the compound.

Named as the suspect 276 reports of 1,000+ that mention it at all

Serious outcome 88% hospitalisation, emergency room or worse

Other Serious or Important Medical Event211

Hospitalization58

Other Serious Outcome30

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

Works better with

3 documented

Magnesium

Essential cofactor for vitamin D metabolism

Required for conversion enzymes · level A

Vitamin K2

Directs calcium to bones, prevents arterial calcification

Activates vitamin K-dependent proteins · level B

Calcium

D2 optimizes calcium absorption and utilization

Enhances intestinal calcium absorption · level A

What not to take with Vitamin D2 (Ergocalciferol)

2 documented

Vitamin D3

May compete with D3 for binding proteins

Competition for vitamin D-binding protein · moderate significance

Excessive Calcium

High calcium may reduce D2 effectiveness

Feedback inhibition of vitamin D activation · mild significance

Medication interactions

Discuss these with a pharmacist before combining

thiazide-diuretics Moderate

Increases calcium retention risk

What to do: Monitor calcium levels

steroids Moderate

Reduces vitamin D effectiveness

What to do: May need higher D2 doses

anticonvulsants Moderate

Increases vitamin D metabolism

What to do: Monitor vitamin D status

Available forms

bioavailability compared

Ranks 3 of 3 among vitamin d forms. Vitamin D3 (Calcidiol) absorbs better — 95%. Compare all forms →

Ergocalciferol (D2) 60

Ergocalciferol (D2): Vegan-suitable, Plant-derived, Ethical choice, Available by prescription

Food sources

before you supplement

UV-treated mushrooms 400-600 IU/100g · 70

Fortified plant milks 100-144 IU/100ml · 60

Fortified cereals 40-100 IU/serving · 65

Note: Very few natural food sources of D2 Mainly found in supplements and fortified foods · 60

Too little

deficiency signs

Same as vitamin D3 deficiency:
Fatigue and weakness
Bone pain and muscle aches
Frequent infections
Depression and mood changes
Hair loss
Delayed wound healing

Too much

toxicity signs

Nausea and vomiting
Kidney stones
Hypercalcemia
Heart rhythm abnormalities
Confusion
Excessive thirst and urination

Who benefits most

vegans-strict

Only plant-based vitamin D option available

2000-4000 IU daily (higher than D3)

vegetarians-ethical

Prefer non-animal derived supplements

2000-4000 IU daily

religious-dietary-restrictions

Some religions require plant-based supplements

2000-4000 IU daily

allergic-to-d3-sources

Cannot tolerate lanolin-derived D3

2000-4000 IU daily

prescription-users

Many prescription vitamin D medications are D2

Physician-determined

Where to buy it

compare forms first

Look for Vitamin D2 (Ergocalciferol) at 2000-4000 IU per serving. The form that matters here is Ergocalciferol (D2).

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What else affects it

Beyond other supplements

Excessive calcium

High calcium may reduce D2 effectiveness

Feedback inhibition of vitamin D activation

How it works

Converted to 25(OH)D2 in liver (less efficiently than D3)
Further converted to calcitriol in kidneys
Binds to vitamin D receptors (lower affinity than D3)
Regulates calcium absorption and bone mineralization
Modulates immune system function
Influences gene expression (fewer genes than D3)

Key findings

what the evidence supports

Less effective than D3 at raising 25(OH)D levels (AJCN 2004)
Suitable for vegans - only plant-based vitamin D option
Shorter half-life requires more frequent dosing
May compete with D3 metabolism when taken together

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Vitamin D2 (Ergocalciferol)?

Documented effects: Bone health support; Immune system support; Vegan-suitable option; Deficiency prevention. Supports calcium absorption and bone mineralization

How much Vitamin D2 (Ergocalciferol) should you take per day?

The common daily range is 2000-4000 IU. By goal — maintenance: 2000-3000 IU; therapeutic: 4000-8000 IU; maximum: 10000 IU; d3 equivalent: 1000 IU D2 ≈ 700 IU D3.

When is the best time to take Vitamin D2 (Ergocalciferol)?

Morning with fat. First effects are typically reported within 2-4 weeks for blood level changes.

What are the side effects of Vitamin D2 (Ergocalciferol)?

At excessive doses: Nausea and vomiting, Kidney stones, Hypercalcemia, Heart rhythm abnormalities, Confusion. Safety rating at normal doses is 8 out of 10.

What should you not take with Vitamin D2 (Ergocalciferol)?

Separate it from Vitamin D3, Excessive Calcium by two to four hours. May compete with D3 for binding proteins

Does Vitamin D2 (Ergocalciferol) interact with medications?

Documented interactions with thiazide-diuretics, steroids, anticonvulsants. Discuss these with a pharmacist before combining.

How much Vitamin D2 (Ergocalciferol) is too much?

The tolerable upper intake level is 100 mcg (4000 IU) per day for adults, per NIH ODS. Above that, the risk of adverse effects rises: Nausea and vomiting, Kidney stones, Hypercalcemia.

How do you know if you need Vitamin D2 (Ergocalciferol)?

The marker is 25(OH)D (measures both D2 and D3), optimal range 40-60 ng/mL (100-150 nmol/L). Common deficiency signs: Same as vitamin D3 deficiency:, Fatigue and weakness, Bone pain and muscle aches, Frequent infections.

Taken for

59 Immunity

Vitamin D3 · Vitamin C (Ascorbic Acid) · Comprehensive Immune Support Complex

38 Joints & Bones

Vitamin D3 · Calcium Carbonate · Bovine Collagen