Biotin probably isn’t
your answer. Your ferritin
number might be.
Search “why is my hair falling out” and you’ll get a different confident answer from every source — biotin, stress, genetics, your shampoo. The honest picture is that hair loss has a few genuinely distinct causes, and they call for completely different responses. The most heavily marketed nutrient for this — biotin — has surprisingly weak evidence behind it. The one that actually matters most is quieter, and often hiding behind a blood test result that looks “normal” but isn’t telling the whole story.
Worth being upfront: hair loss has many possible causes, and this page covers the nutritional and lifestyle angles specifically. Patchy, sudden, or scalp-related hair loss deserves a dermatologist’s evaluation, not a guess.
The three genuinely distinct causes worth telling apart
Hair loss generally traces back to one of three categories: genetics (a permanent, patterned process), stress (a temporary, all-over shedding phase), or nutrient deficiency (a correctable, testable factor). Knowing which one you’re actually dealing with changes what will and won’t help.
Most hair-loss content treats every cause as interchangeable and every fix as equally likely to work. It isn’t that simple, and pretending otherwise wastes time and money. The three broad categories genuinely behave differently: genetic hair loss follows a predictable pattern and doesn’t respond to diet. Stress-related shedding is temporary, diffuse, and usually resolves on its own. Nutrient-related hair loss is the one category that’s actually testable and correctable — but only for the nutrients where the evidence is real, which, as you’ll see, isn’t the one most marketing dollars go toward.
Genetics — the most common cause, and nutrition can’t reverse it
Genetic pattern hair loss, called androgenetic alopecia, is driven by an inherited sensitivity to a hormone called DHT, causing gradual, patterned thinning — a receding hairline or crown thinning in men, diffuse thinning at the part line in women. Nutrition does not reverse this underlying process.
This is the single most common cause of hair loss overall, and it’s important to say plainly: no supplement fixes this. It’s driven by genetics and hormone sensitivity, not nutrient status, and it shows up as a distinctive, progressive pattern rather than all-over thinning. General nutritional adequacy still matters for overall hair health alongside it, but it isn’t a treatment for the underlying process.
Stress — the delayed, diffuse shedding phase
Stress-related hair loss, called telogen effluvium, causes diffuse, all-over shedding that shows up two to three months after a significant stressor — illness, surgery, major life stress, or rapid weight loss. It typically resolves once the trigger passes.
Here’s the mechanism in plain terms: hair follicles cycle between an active growth phase and a resting phase. A significant physical or emotional shock can push an unusually large number of follicles into the resting phase all at once. Because of how the hair cycle works, this shows up as noticeable shedding two to three months later — which is exactly why people often don’t connect the dots between a stressful event and the hair loss that follows. Once the underlying trigger passes, this type of shedding generally resolves on its own, though the delay applies on the way out too.
The biotin myth — genuinely weaker evidence than the marketing suggests
True biotin deficiency is rare in people eating a varied diet, and there is no robust clinical trial evidence that biotin supplementation improves hair growth in people with normal biotin levels. Even among confirmed biotin-deficient patients, only about 23% reported improvement with supplementation.
Biotin is, by a wide margin, the most heavily marketed nutrient for hair growth — and the evidence behind it is genuinely the weakest of everything covered on this page. True deficiency is rare, since biotin is found in many everyday foods and your gut bacteria produce some of it too. It becomes more relevant in specific situations: pregnancy and breastfeeding, chronic alcohol use, certain long-term medications, and malabsorption conditions. One study did find deficiency in 38% of women specifically presenting with hair loss — worth knowing, though this likely reflects a population already more prone to deficiency for other reasons, not evidence that biotin deficiency is common generally.
High-dose biotin can distort your blood test results
This is a real, underappreciated issue: many “hair, skin, nails” products contain very high doses of biotin (5,000 micrograms or more). At these doses, biotin can interfere with common laboratory tests, producing falsely abnormal thyroid function and cardiac troponin results — results a doctor might otherwise act on. Drug safety authorities have issued formal warnings about this. Always tell your doctor or lab technician if you’re taking high-dose biotin before any blood test.
The iron reality — not a myth, but more nuanced than “just take iron”
Iron deficiency, measured through ferritin, is the best-evidenced nutritional cause of hair loss. But the ferritin level considered healthy for hair (around 50-70 ng/mL) is meaningfully higher than the standard threshold used to diagnose anemia (around 10-15 ng/mL) — so a “normal” iron test doesn’t necessarily rule this out.
Unlike biotin, iron’s connection to hair loss is genuinely well-supported — studies have found meaningfully lower average ferritin (a blood marker reflecting your body’s stored iron) in people with hair loss compared to healthy controls, and small clinical trials have shown real improvement when actually-deficient women were treated with iron. This is particularly relevant for menstruating women.
Here’s the detail that matters most, and the one most people never hear: labs typically flag ferritin as “low” only around 10-15 ng/mL — the threshold for full iron-deficiency anemia. But research specifically on hair follicles points to a considerably higher threshold, commonly cited around 50-70 ng/mL, as what’s actually needed for healthy hair growth. That means someone can get a “normal” result on a standard iron test and still be running low enough to affect their hair.
“A normal iron test and a ferritin level low enough to affect your hair can be the same result — the lab’s cutoff and the hair-health cutoff simply aren’t the same number.”
Why “my iron is fine” isn’t always the full pictureThis is exactly why iron isn’t something to supplement blindly. Unlike most vitamins, too much iron is also a real problem — iron overload is itself a documented, if less common, cause of hair loss, alongside its other health risks. If iron deficiency is genuinely a factor, the right first step is a specific ferritin test, not a guess.
Other nutrients worth knowing about
Genuinely relevant nutrients
Real, documented connections
Worth remembering
Context that matters
Our zinc deficiency guide and vitamin D deficiency guide cover these two in more depth if either seems relevant to you.
When this is worth a doctor’s visit
Some patterns need a dermatologist, not a supplement
Patchy, sudden, or rapidly progressing hair loss, or hair loss accompanied by scalp itching, redness, or other changes, deserves a proper dermatologist evaluation rather than a supplement-first approach. These patterns can point to conditions beyond diet, genetics, or stress that need their own specific evaluation.
Why our multivitamin deliberately leaves iron out
If iron deficiency is genuinely a tested, confirmed factor in someone’s hair loss, that’s a real, correctable situation — but it needs to be addressed with an actual ferritin test and targeted supplementation, not folded into a daily multivitamin everyone takes regardless of their iron status. Many adults, particularly men and postmenopausal women, already have adequate or even excess iron — which is exactly why EVO HOMINUS’s multivitamin is formulated without iron. What we do include: active methylcobalamin B12 and P5P B6, both genuinely relevant to hair and nerve health, dosed at levels appropriate for daily use by everyone, not just people with a specific tested deficiency.
What to actually do if your hair is shedding more than usual
Hair loss causes, answered plainly.
More from the EVO HOMINUS knowledge hub
Why Your Daily Multivitamin Shouldn’t Contain Iron
The full reasoning behind EVO HOMINUS’s iron-free formula.
Read the guide → Science HubZinc Deficiency in India — Symptoms Most People Miss
Another nutrient with a real, documented hair connection.
Read the guide → Science HubVitamin D Deficiency in India — Why Most of Us Are Low Despite the Sun
Widespread, commonly missed, and linked to hair thinning too.
Read the guide →