What Works Skin — Independent · Evidence-First · Ad-FreeIssue 014 · 20 April 2026 · Next: 04 Maywhatworksskin.com
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Supplement · Barrier & inflammation · Vitamin D

P. 18 · BRIEF

Vitamin D.

Test 25(OH)D first. Most Indian adults are insufficient.

Insufficiency is genuinely common in adults across India — including in those with substantial sun exposure — for reasons that have to do with skin pigment, sunscreen use, and behavioural patterns. The eczema and acne literature is mixed; the case for repletion in confirmed deficiency is unambiguous.

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— § 02

What the literature shows.

Atopic dermatitis (with deficiency)
Multiple RCTs

Repletion meaningfully reduces flare severity in patients with low baseline 25(OH)D. Less effect in already-replete patients.

70%
Acne severity
Mixed observational

Lower 25(OH)D associated with more severe acne in observational studies. Repletion trials are smaller and less consistent.

45%
Hair shedding (with deficiency)
Case series

Real association in observational data. Repletion can support recovery alongside iron and ferritin work.

55%
Skin lightening / brightening
—

Not the indication. Marketing claim that the literature does not support.

10%
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— § 03

Forms and bioavailability.

Cholecalciferol (D3) 1000 IU/d

Absorption · Good

Most-studied form. Daily dosing matches the kinetic profile better than mega-doses.

Cholecalciferol 60,000 IU weekly

Absorption · Good

Common Indian prescription protocol. Convenient; equivalent endpoints to daily.

Cholecalciferol 60,000 IU monthly

Absorption · Good

Maintenance after repletion. Adjust to achieve target 25(OH)D.

Ergocalciferol (D2)

Absorption · Moderate

Vegetarian source (fungi-derived). Less efficient at raising 25(OH)D than D3.

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Bottom line

The cheapest blood test in the supplement aisle. Test before supplementing; replete to target; then maintain with the lowest effective dose.

⁂

— § 04

Frequently asked.

Why are Indian adults so often insufficient?

A combination of pigmented skin (which makes more UV exposure necessary for the same vitamin D synthesis), modern indoor lifestyles, sunscreen use, traditional clothing patterns in some communities, and insufficient dietary fortification. Population studies repeatedly show 60–80% of Indian adults below the 30 ng/mL threshold.

What target should I aim for?

Most dermatology references suggest 30–50 ng/mL (75–125 nmol/L) of 25(OH)D as the maintenance target. Below 20 ng/mL is overt deficiency requiring loading-dose protocols. Above 80 ng/mL is unnecessary and approaches the safety ceiling.

How long until effect?

25(OH)D normalises in 8–12 weeks of consistent supplementation. Skin endpoints (eczema flare reduction, hair recovery) take an additional 8–12 weeks beyond that. Plan for 6 months total before judging.

Toxicity concern?

Real but at much higher chronic doses than skin protocols use. Sustained intake above 10,000 IU/d for months can cause hypercalcemia. The standard 1000 IU/d or weekly 60,000 IU regimens sit well below the toxicity threshold.