How Low Ferritin Causes Hair Loss
Hair follicles are among the most metabolically active cells in the body. They require a constant supply of nutrients — including iron — to maintain the anagen (growth) phase of the hair cycle. When iron stores fall, the body prioritises directing available iron to essential functions: oxygen transport in red blood cells, cardiac muscle function, immune defence.
Hair follicles are considered non-essential by the body's triage system. When ferritin drops below a functional threshold, follicles are pushed prematurely into the telogen (resting) phase. After 2–3 months in telogen, these hairs shed. The clinical result is telogen effluvium — diffuse hair shedding, often across the whole scalp, that can begin months after the period of iron depletion.
This delay is one reason iron deficiency hair loss is so commonly missed. Patients present with shedding, their blood tests reveal low ferritin — but because the shedding started months after the ferritin dropped, the connection is not always made.
Which Ferritin Level Is Associated With Hair Shedding?
The research consistently points to ferritin levels below 30 µg/L as being associated with hair loss, and levels below 15 µg/L show a particularly strong correlation with active shedding. However, there is individual variation — the relationship is not a precise threshold but a gradient of risk.
Important: Other conditions also cause hair shedding — thyroid disease (both over- and under-active), polycystic ovary syndrome (PCOS), hormonal changes around menopause, and androgenetic alopecia. It is important to check thyroid function and hormonal markers alongside iron studies before concluding that iron is the sole cause. Our GP can arrange a comprehensive panel.
Why Iron Tablets May Not Be Enough
Oral iron supplements can restore ferritin — but they have real limitations, particularly when it comes to hair loss:
- Speed: Oral iron typically takes 3–6 months to meaningfully restore ferritin. Hair regrowth begins only once ferritin is restored. A slow correction means months more shedding before the follicles recover.
- Gut side effects: Nausea, constipation, and stomach cramps lead many patients to reduce their dose or stop taking tablets altogether — making the timeline even longer.
- Absorption variability: Gut absorption of iron is highly variable and can be reduced by coeliac disease, gastritis, or even dietary factors. Some patients take oral iron faithfully for months with minimal ferritin improvement.
How IV Iron Can Accelerate Hair Recovery
An IV iron infusion bypasses the gut entirely, delivering iron directly into the bloodstream. Ferritin typically rises significantly within four to six weeks of a single infusion — a timeline that would take three to six months to achieve with oral supplements in most patients.
For hair loss specifically, this matters enormously. The sooner ferritin is restored, the sooner follicles can return to the growth phase, and the sooner shedding slows. Clinical experience and patient reports consistently indicate that visible shedding reduction occurs at 2–3 months after an infusion, with new regrowth visible at 3–6 months.
Oral iron timeline
- 3–6 months to restore ferritin
- Add 2–3 months before shedding slows
- Add 3–6 months for visible regrowth
- Total: up to 12–15 months to full recovery
IV iron timeline
- 4–6 weeks to restore ferritin
- 2–3 months before shedding slows
- 3–6 months for visible regrowth
- Total: 4–8 months to full recovery
What to Expect After an Iron Infusion for Hair Loss
It is important to set realistic expectations. An iron infusion does not stop shedding overnight — it restores the stores that allow follicles to recover. Here is what most patients experience:
- Weeks 1–6: Ferritin rising. Hair shedding may continue — this is expected.
- Months 2–3: Shedding begins to slow as follicles enter the growth phase.
- Months 3–6: Short new hairs become visible — often noticeable as baby hairs at the hairline.
- Months 6–12: Density continues to improve as the new hairs grow to full length.
We recheck ferritin at six weeks. If further infusions are needed to reach the optimal ferritin target (ideally above 50–70 µg/L for hair recovery), these are planned at that review.
Book an Iron Assessment
If you are experiencing hair shedding and have reason to suspect low iron, book an iron assessment at Lambert Medical Practice. We arrange a comprehensive blood panel including ferritin, full blood count, thyroid function, and hormonal markers to identify the cause — then create a treatment plan to address it.