Iron deficiency is the most common nutritional cause of hair loss worldwide, particularly in women of reproductive age. Hair follicles require ferritin levels above 40 ng/mL for optimal function, well above the 12 ng/mL threshold that standard lab work considers "normal." Correcting iron stores leads to regrowth in most patients within 3 to 6 months.
This article is for informational purposes only and does not constitute medical advice.
Why Iron Matters for Hair
Hair follicle cells are among the fastest dividing cells in the body. They require a steady supply of oxygen and nutrients delivered via the bloodstream. Iron is the core component of hemoglobin, the molecule in red blood cells that carries oxygen. When iron stores drop, the body prioritizes oxygen delivery to vital organs (heart, brain, kidneys) and reduces supply to non-essential tissues, including hair follicles.
This is why hair loss is often one of the earliest signs of iron deficiency, appearing before a person develops full iron-deficiency anemia.
The Iron-Hair Connection Chain
| Step | What Happens |
|---|---|
| 1. Iron stores decline | Ferritin drops below optimal levels |
| 2. Oxygen delivery decreases | Follicles receive less oxygen and fewer nutrients |
| 3. Growth phase shortens | Follicles enter resting phase (telogen) prematurely |
| 4. Shedding increases | Diffuse hair loss appears 2-4 months later |
| 5. Hair quality declines | Remaining hair becomes thinner and more brittle |
Ferritin Levels and Hair Health
What the Numbers Mean
| Ferritin Level | Lab Classification | Hair Impact |
|---|---|---|
| Below 12 ng/mL | Deficient | Significant shedding, very likely hair loss |
| 12 to 30 ng/mL | Low normal (by lab standards) | Hair loss likely, especially with other stressors |
| 30 to 40 ng/mL | Normal (lab) but suboptimal for hair | Hair may thin gradually |
| 40 to 70 ng/mL | Optimal minimum for hair growth | Target range for most dermatologists |
| 70 to 100 ng/mL | Ideal | Best environment for hair follicle function |
| Above 200 ng/mL | Elevated | May indicate inflammation or hemochromatosis, investigate |
The critical point: a ferritin of 15 ng/mL is technically "within range" on most lab reports. Your doctor might say your iron is fine. But from a hair health perspective, it is far below the threshold needed for normal follicle function. Always ask for the actual number rather than accepting "normal" as sufficient.
Who Is at Risk
High-Risk Groups for Iron-Related Hair Loss
| Group | Why |
|---|---|
| Women with heavy menstrual periods | Monthly blood loss depletes iron stores |
| Pregnant and postpartum women | Increased iron demands and blood volume changes |
| Vegetarians and vegans | Plant-based iron (non-heme) has lower absorption rates |
| Frequent blood donors | Regular blood loss without adequate replacement |
| Endurance athletes | Increased iron turnover and foot-strike hemolysis |
| People with GI conditions | Celiac, Crohn's, ulcerative colitis impair absorption |
| Post-gastric bypass patients | Reduced stomach acid and absorption surface |
Women are disproportionately affected. Studies estimate that 30 to 40% of premenopausal women have ferritin levels below 40 ng/mL. This is a leading reason why diffuse hair thinning is so common in women aged 20 to 50.
How to Test
Ask your doctor for a "ferritin" blood test. This measures stored iron and is the most sensitive marker for early iron depletion. A complete iron panel includes:
| Test | What It Measures | Optimal for Hair |
|---|---|---|
| Ferritin | Stored iron | Above 40 ng/mL (ideally 70+) |
| Serum iron | Iron circulating in blood | 60 to 170 mcg/dL |
| TIBC | Total iron-binding capacity | 250 to 370 mcg/dL |
| Transferrin saturation | Percentage of iron-binding sites filled | 20 to 50% |
| Hemoglobin | Oxygen-carrying capacity | Above 12 g/dL (women), 13.5 g/dL (men) |
Ferritin alone is sufficient for screening. If ferritin is low, the full panel helps determine whether you have true iron deficiency or another condition affecting iron metabolism.
Treatment
Supplementation Protocol
| Ferritin Level | Supplement Type | Dose | Duration |
|---|---|---|---|
| Below 15 ng/mL | Ferrous sulfate or ferrous bisglycinate | 65 to 100 mg elemental iron, twice daily | 3 to 6 months |
| 15 to 30 ng/mL | Ferrous bisglycinate or iron polysaccharide | 25 to 65 mg elemental iron, once daily | 3 to 4 months |
| 30 to 40 ng/mL | Gentle iron (bisglycinate) or food-based | 18 to 25 mg elemental iron, once daily | 2 to 3 months |
Tips for Better Absorption
| Do | Do Not |
|---|---|
| Take with vitamin C (orange juice, berries) | Take with calcium supplements or dairy |
| Take on an empty stomach if tolerated | Take with coffee or tea (tannins block absorption) |
| Space 2 hours from other supplements | Take at the same time as antacids or PPIs |
| Choose bisglycinate for fewer GI side effects | Rely solely on plant-based iron if severely deficient |
Recheck ferritin 8 to 12 weeks after starting supplementation. Adjust the dose based on results. Continue supplementation until ferritin reaches at least 40 ng/mL and ideally above 70 ng/mL, then switch to a maintenance dose or dietary approach.
Iron deficiency commonly occurs alongside vitamin D deficiency, especially in women. If you are addressing iron, check vitamin D as well. Read our vitamin D and hair loss guide for the full picture.
When It Is Not Just Iron
If your ferritin is above 70 ng/mL and you are still losing hair, iron is not your problem. Patterned hair loss (thinning at temples and crown) points to androgenetic alopecia, which requires different treatment. Use our Norwood scale guide to assess your pattern.
Next Step
Upload a photo at myhairline.ai/analyze to check whether your hair loss pattern looks nutritional (diffuse) or hormonal (patterned), and get a personalized next step.