What Works Skin — Independent · Evidence-First · Ad-FreeIssue 014 · 20 April 2026 · Next: 04 Maywhatworksskin.com
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Supplement · Hair & nails · Iron

P. 16 · BRIEF

Iron.

Test ferritin first. Treat the cause, not the symptom.

The single most common reversible cause of telogen effluvium in adult women. The supplement that genuinely changes outcomes — but only when you have actually documented low ferritin first. Empirical iron supplementation without testing is an avoidable category of harm.

⁂

— § 02

What the literature shows.

Telogen effluvium with low ferritin
Multiple observational series

Strongly replicated. Serum ferritin <30 ng/mL in shedding patients should prompt iron repletion.

85%
Hair shedding with normal ferritin
Null trials

Iron does not help shedding when iron status is already adequate. The evidence here is clear.

15%
Pattern hair loss (AGA)
Mixed

Iron is not a treatment for androgenetic alopecia, though deficiency may worsen it. Repletion alongside minoxidil/finasteride.

25%
Eyebrow / lash thinning with low ferritin
Case series

Same logic as scalp hair. Repletion often restores periorbital hair quality over 6 months.

55%
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— § 03

Forms and bioavailability.

Ferrous sulphate 200 mg

Absorption · Good

Cheapest, most-evidenced. GI side effects are the limiter (constipation, dark stool, nausea).

Ferrous bisglycinate (chelated)

Absorption · Good

Better tolerated. Premium pricing; equivalent endpoints in repletion trials.

Ferrous gluconate

Absorption · Moderate

Lower elemental iron per tablet. Useful as gentler bridging dose.

IV iron (clinic)

Absorption · 100%

For severe deficiency, malabsorption, or oral intolerance. Faster repletion; clinic-administered.

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Bottom line

The supplement that genuinely matters in shedding — but only after you have tested. Spend the small amount on the ferritin test before spending the much-larger amount on supplements you may not need.

⁂

— § 04

Frequently asked.

What ferritin level should trigger treatment?

Different bodies use different thresholds. Most trichology references treat ferritin <30 ng/mL as actionable in shedding patients, with a target of >70 ng/mL for hair-cycle restoration. Below 12 ng/mL is overt deficiency requiring repletion regardless of hair status.

Why not supplement empirically?

Iron overload (hemochromatosis, transfusion-dependent thalassemia, etc.) is more common than commonly recognised, and chronic over-supplementation can cause real organ damage. The 30-rupee ferritin test is dramatically cheaper than the consequences of empirical supplementation in someone iron-replete.

Why does it take so long to see hair improvement?

Hair grows ~1 cm per month. Even after ferritin normalises, the hair cycle restoration takes 4–6 months to be visible at the scalp. Photograph at week 0 and month 6 — month 3 photos rarely show the change.

Should I take vitamin C with it?

Yes — vitamin C ~250 mg with each iron dose meaningfully increases absorption. Avoid taking iron with calcium, coffee, tea, or dairy, all of which inhibit absorption.