Vitamins for hair loss in women: evidence and limits
Reviewed by the My London Pharmacy clinical team, Zaynab Ali, Pharmacist Independent Prescriber
·17 August 2026
·6 min read
Quick answer
Vitamin and mineral supplements can help hair loss in women, but only when a genuine deficiency is driving the shedding, most commonly iron, and less consistently vitamin D, zinc or biotin. Taking supplements without a deficiency is unlikely to help and, for some nutrients, can cause harm at high doses. Testing before supplementing is the evidence-based approach.
The honest picture: supplements help deficiencies, not hair loss in general
Hair-loss supplements are marketed heavily, and the evidence behind them is more limited than the marketing suggests. The clearest, best-supported finding across the research is this: correcting a genuine nutrient deficiency can improve hair shedding linked to that deficiency. Taking the same supplement without a deficiency, hoping it will help regardless, has much weaker evidence behind it, for most nutrients, more is not better once your levels are already adequate.
That distinction matters because it changes the sensible first step: testing to see whether a deficiency is actually present, rather than starting a supplement and hoping.
Iron: the best-supported link
Of all the nutrients linked with hair loss, iron has the strongest evidence, particularly in women, where low ferritin (iron stores) is common due to menstrual blood loss. Correcting a genuine iron deficiency, guided by a blood test rather than guesswork, is more likely to help hair shedding than almost any other single supplement, our guide to blood tests for hair loss explains how ferritin is checked and interpreted.
Iron supplements are not risk-free at high doses, and taking them without a confirmed deficiency will not help hair that is shedding for a different reason, testing first avoids both problems.
Vitamin D and zinc: real but less consistent evidence
Both vitamin D and zinc deficiency are associated with hair shedding in research, though the evidence is less consistent than for iron, some studies show a clear link, others do not. Vitamin D deficiency is common in the UK, especially in winter, and correcting it is reasonable and low-risk when a test confirms low levels; see our guide to what your vitamin D result actually means.
Zinc deficiency is less common in people eating a varied diet, but can occur with restrictive diets, certain digestive conditions, or prolonged illness. As with iron, the evidence supports correcting a genuine shortfall, not taking high-dose zinc indiscriminately, excess zinc can itself interfere with copper absorption and cause problems.
Biotin: popular, but the evidence is thin
Biotin is probably the most heavily marketed hair-loss supplement, and it is worth being clear-eyed about it: genuine biotin deficiency is rare, and there is limited good evidence that biotin supplements improve hair growth in people who are not actually deficient. Most people taking biotin supplements for hair loss are unlikely to be deficient in the first place.
There is also a practical downside worth knowing: high-dose biotin can interfere with certain blood test results, including thyroid tests, which is precisely the kind of test used to investigate hair loss in the first place. Most labs recommend stopping biotin supplements for at least two days before blood tests to avoid a misleading result.
Protein and overall nutrition
Hair is made largely of protein, and significant, prolonged inadequate protein intake, from restrictive dieting, illness, or an eating disorder, can contribute to hair thinning. This is less about a specific supplement and more about overall dietary adequacy: crash diets and very low-calorie eating are a recognised, if often overlooked, cause of temporary hair shedding, generally improving once normal eating resumes.
General nutritional adequacy supports healthy hair growth the way it supports every other tissue in the body, it is rarely the single dramatic fix marketing suggests, but it is a genuine foundation worth getting right.
If you are supplementing: what to look for
If testing confirms a genuine deficiency, the practical next question is what to actually take. For iron, the dose and form matter, your clinician will usually recommend a specific supplement and duration based on how low your ferritin is, since over-the-counter multivitamins rarely contain enough iron to correct a real deficiency, and taking iron alongside vitamin C can improve how well it is absorbed. For vitamin D, a standard daily dose is usually sufficient for mild insufficiency, while a genuinely deficient result often warrants a higher-dose loading course first.
General "hair, skin and nails" multivitamin blends are rarely the most efficient way to correct a specific, confirmed deficiency, they typically contain small amounts of many things rather than a therapeutic dose of the one nutrient you actually need. Once you know what is genuinely low, a targeted supplement at an appropriate dose, ideally guided by a clinician, is a more direct route than a general blend.
What supplements can't do
It is worth being realistic about the limits here, whatever the underlying cause turns out to be. Supplements, even the right ones, correcting a genuine deficiency, will not reverse hair loss caused by other factors: genetic pattern hair loss, hormonal conditions like polycystic ovary syndrome, autoimmune hair loss, or hair loss from certain medications. Taking a multivitamin marketed for hair growth when your nutrient levels are already normal is unlikely to meaningfully change a cause rooted somewhere else entirely.
The hair growth cycle is also inherently slow, each hair spends months in a resting phase before shedding and being replaced, so even when a supplement is genuinely addressing the right cause, visible improvement typically takes three to six months of consistent correction, not days or weeks. Expecting a fast result, from the right intervention or the wrong one, tends to lead to giving up on a treatment that might otherwise have worked, or persisting with one that never would.
Test, don't guess
The practical takeaway across all of this: if you are considering supplements for hair loss, a blood test to check for an actual deficiency is a better starting point than trying products one at a time. It tells you whether a nutritional cause is even likely, avoids wasting money and time on supplements that will not help, and flags any dosing that needs a clinician's input rather than guesswork, particularly for iron and zinc, where high doses without a deficiency carry their own risks.
If nutrient levels come back normal, that is useful information too, it points towards other causes worth discussing with a clinician, from hormonal factors to typical pattern hair loss, covered in our hair loss treatment options guide.
Frequently asked questions
Do hair-loss vitamins actually work?
Only reliably when they correct a genuine deficiency, iron has the strongest evidence, followed by vitamin D and zinc. Taking supplements without a confirmed deficiency has much weaker evidence behind it.
Is biotin worth taking for hair loss?
Genuine biotin deficiency is rare, and evidence that biotin helps people who are not deficient is limited. High-dose biotin can also interfere with thyroid blood tests, so it is worth being cautious about taking it without reason.
Should I test before taking hair-loss supplements?
Yes, a blood test shows whether a nutrient deficiency is actually present, which is a more evidence-based starting point than trying supplements without knowing.
Can too much iron or zinc be harmful?
Yes. Both can cause problems at high doses if taken without a confirmed deficiency, which is another reason to test rather than supplement speculatively.
Can crash dieting cause hair loss?
Yes. Significant, prolonged inadequate calorie or protein intake is a recognised cause of temporary hair shedding, which generally improves once normal eating resumes.