Iron deficiency and hair loss: Which nutrients really matter

It usually happens quite inconspicuously: When you comb your hair, suddenly more hairs get caught in the brush, or noticeably more collects in the drain than a few months ago. Suspicion quickly falls on a nutrient deficiency, above all iron, because hardly any other connection comes up as often in conversations among friends or at the doctor's office.

There is indeed a plausible biological mechanism behind it that explains why depleted iron stores can affect the hair cycle at all. However, the research on this is far less clear-cut than everyday logic would suggest, and not every case of diffuse hair loss has to do with iron stores. In this article, we look at what your ferritin level really reveals about your hair, which other nutrients can play a role and when a doctor's appointment is the most sensible first step.

Iron deficiency and hair loss: how the deficiency sends hair into the resting phase

Your hair roots need iron because they are among the busiest dividing cells in the entire body. When iron runs short, the body first economizes where it isn't vital. Unfortunately, hair is one of those places.

Every hair goes through a fixed cycle. In the growth phase (experts call it the anagen phase), it grows for years. This is followed by a short transition period and finally the resting phase, the telogen phase, which lasts a few months. At the end, the hair falls out, and a new one grows back in the same spot.

Ferritin is the protein in which your body stores iron. When these stores drop, the growth phase of many hairs gets shorter. More hairs slip into the resting phase at the same time and then fall out together. As a result, the hair thins evenly across the whole head.

The catch: This happens with a delay. Between the onset of the deficiency and the moment you notice it in your brush, there are usually weeks to months.

In short: Doctors use the term telogen effluvium for diffuse hair loss in which a conspicuously large number of hairs switch to the resting phase at the same time. Triggers can be a nutrient deficiency, but also infections, surgery, severe stress or hormonal changes.

To be honest, though, research is divided on this. Some observational studies found lower ferritin levels on average in women with heavy hair loss. A case-control study with 90 affected women and 90 controls, on the other hand, found no significant difference in ferritin (1). The authors conclude that nutrient deficiencies are less common in this form of hair loss than assumed. They recommend individual assessment and advise against blanket multivitamin products.

So iron deficiency is a possible trigger, and one that can be measured well. But it's not the only one.

These blood values really tell the doctor something

The decisive clue comes from the ferritin level. It shows how full your iron stores are and is therefore considered the most meaningful lab value when it comes to iron deficiency.

Serum iron, that is, the iron currently circulating in the blood, fluctuates over the course of the day and with your last meal. The hemoglobin value (the red blood pigment) only drops once the deficiency is well advanced. A normal blood count therefore doesn't mean by a long shot that your stores are full.

Ferritin can't be looked at in isolation. With inflammation, infections or chronic diseases, the value can come out higher than the stores are actually filled. That's why your doctor looks at several values together, for example also an inflammation marker such as CRP, and at the same time rules out other causes of diffuse hair loss, such as the thyroid.

So your next step is an appointment with your family doctor or a dermatologist. Feel free to tell them since when you've noticed the hair loss and whether anything changed in the months before, such as an illness, a lot of stress or a new way of eating. That helps enormously in interpreting the findings correctly.

Good to know: If you're already taking a product with biotin, such as a hair vitamin, mention it before your blood is drawn. Biotin can interfere with certain lab tests, including thyroid values.

Tiredness, by the way, is often discussed in the same breath as iron. If you want to learn more about this topic, this article might interest you: causes of tiredness despite enough sleep.

Vitamin D, zinc, B12, biotin: the state of research

The research is thin and inconsistent. The evidence is clearest for zinc. For vitamin D and B12, a lot is still open, and according to current knowledge biotin only helps if there really is a deficiency. A systematic review on supplementation for hair loss describes the body of evidence overall as thin and inconsistent (3).

Zinc shows initial evidence: In the case-control study, the affected women had significantly lower zinc levels (1), and the review links zinc deficiency to telogen effluvium and hair breakage (3). Vitamin D and B12 remain unclear: Some studies found low levels in people with hair loss, others such as the case-control study show no difference (1, 3), and whether hair actually grows back thicker after deficiencies have been corrected has not been properly studied.

Biotin is well documented, but only in the case of a genuine deficiency: Case reports show a benefit when a deficiency has been confirmed; for people without a deficiency, no effect on hair has been demonstrated, and with a balanced diet, biotin deficiency is rare.

Zinc is worth a second look. A genuine deficiency is rather rare with a normal diet and occurs mainly with certain intestinal diseases or after gastrointestinal surgery. In addition, the value in blood serum reflects the actual zinc status only to a limited extent. So a slightly low lab value doesn't automatically mean that zinc is behind your hair loss.

Why women are affected more often

Women lose blood, and therefore iron, with every period, and correspondingly more with heavy bleeding. If you eat a vegan or vegetarian diet, there's a second factor: Plants provide iron in a form that the gut absorbs less well than iron from meat. Vitamin C, for example from bell peppers or citrus fruits, improves absorption, while coffee and black tea taken directly with meals slow it down. It's not without reason that the German Federal Institute for Risk Assessment (BfR) counts iron in women among the nutrients whose supply in Germany is partly critical (2).

Advertisement: For women, POWER | Hormone Balance for Women from CLAV is an option. The capsules combine iron, folic acid and vitamin B12. Iron contributes to normal formation of red blood cells and hemoglobin.

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Which nutrients women should generally keep an eye on is a topic in itself. If you want to learn more about it, this article might interest you: which vitamins really make sense for women.

But more is not better: where food supplements reach their limits

More brings no additional benefit. The BfR considers vitamin and mineral supplements generally unnecessary for healthy people and sees a higher risk of oversupply, especially in people who are already well supplied (2).

Important to know: Some nutrients, such as the fat-soluble vitamins A, D, E and K as well as iron, zinc and selenium, accumulate in the body. For vitamin D, even severe poisoning with kidney damage has been documented after prolonged intake of very high amounts (2). Hair vitamins, multivitamins and single-nutrient products add up, which is why oversupply is most likely to occur when several products with the same nutrients are combined. The percentage on the package (NRV) is not an upper limit but refers to a reference value for labeling. How much is safe is determined by the European Food Safety Authority (EFSA) and the BfR with their own maximum levels.

The sensible approach looks like this: first get tested, then specifically supplement what is actually missing, and check again after some time. With iron and zinc there's also an interaction, because in larger amounts both compete for absorption in the gut. If you need both, it's best to discuss with your doctor's office how to split up the intake sensibly.

Advertisement: If your doctor has determined that you need zinc, CLAV offers Zinc Bisglycinate 25mg with 25 mg of zinc per capsule. Zinc contributes to the maintenance of normal hair.

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As a combination for skin, hair and nails, GLOW | Vitamins for Hair contains biotin, zinc, selenium and natural vitamin C, among other things. Biotin contributes to the maintenance of normal hair. For both, however: Do not exceed the recommended daily intake.

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The path from suspicion to clarity

Even a corrected deficiency doesn't guarantee that your hair will become thicker again, because diffuse hair loss can have several triggers at the same time. The most honest next step is therefore an appointment at a doctor's office where ferritin, an inflammation marker and the thyroid are looked at together. With these findings in hand, you can make a targeted decision about whether a nutrient is really missing, and which one. And if the cause lies elsewhere, you haven't spent money on the wrong product. Hair grows slowly, so give your body time.

Sources

(1) Case-control study on nutrient levels in chronic telogen effluvium (90 patients, 90 controls). Journal of Cosmetic Dermatology. PMC11626366.

(2) Bundesinstitut für Risikobewertung (BfR) and Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL): Statement on vitamins and minerals in food supplements. Bundesgesundheitsblatt. PMC12583368.

(3) Systematic review on supplementation in alopecia. Springer Medizin. DOI: 10.1007/s15012-023-7764-y.

FAQ: Common questions about iron deficiency and hair loss

At what ferritin level are the stores considered too low?

There is no fixed threshold that all practices apply in the same way. Labs work with different reference ranges, and inflammation can skew the value upward. That's why your doctor interprets it together with other blood values.

Do iron tablets do anything for your hair if no deficiency has been shown?

No, there's no evidence for that. According to the BfR, intake beyond your needs has no additional health benefit but increases the risk of oversupply. Iron is also one of the minerals that accumulate in the body.

Should I start taking food supplements before my doctor's appointment?

Waiting is usually the wiser choice. An iron supplement can change your ferritin level, and biotin interferes with some lab tests. With unaltered values, it's much easier to determine exactly what you're really missing.