What Deficiency Causes Ridges in Your Nails? Mostly, None

Almost every page answering this question names a vitamin. The dermatology literature answering the same
question names ageing. Here is the difference, and the one nail change worth acting on.

First: which direction do your ridges run?

This is the whole question, and it takes two seconds.

If yours run lengthwise, the rest of this page is mostly reassurance. If they run across, or the nail is
dished, keep reading for the reason.

Lengthwise ridges: what the numbers actually show

A study of 100 patients aged between 60 and 101 catalogued nail surface changes:

• Prominent longitudinal ridges: 85%
• Rough nails: 33%
• Transverse ridges: 23%
• Lamellar splitting: 15%

Ageing is described in the literature as the most common cause of onychorrhexis, the term for superficial
longitudinal ridging, and mild onychorrhexis is called a common finding in the elderly.

Something present in 85% of a population is not a warning sign. It is what nails do. The nail matrix, the
tissue that manufactures the plate, becomes slightly less uniform over decades, and the plate it produces
picks up fine lengthwise grooves the way an old record picks up surface texture.

The AAD’s phrasing is worth having verbatim, because it is more relaxed than almost anything else written
on this subject:

Lines that run the length of a nail are common and usually nothing to worry about.

The spoon shape is the one that matters

Koilonychia is defined as a thin, brittle, concave nail dystrophy where the nail plate is centrally
depressed and everted laterally. The classic test is that the dip is deep enough to hold a drop of water.

Its association with iron is real and long established:

Classically koilonychia (spoon shaped nails) has been associated with iron deficiency
anaemia, and has been shown to improve with iron supplementation.

And unusually for this subject, the correction is documented and quick. With iron repletion, using
150 to 200 mg of elemental iron, the nail abnormality usually returns to normal
within 4 to 6 months. That is roughly the time it takes a fingernail to grow out entirely, which is
exactly what you would expect if the deficiency was affecting the matrix while the nail was being made.

But read the 5.4% before you conclude anything

Here is the figure that changes how this sign should be used. Koilonychia is found in
5.4% of patients with iron deficiency anaemia.

Nineteen out of twenty people with diagnosed iron deficiency anaemia have nails that look normal.

That cuts in two directions and both are useful:

• Normal nails do not rule out iron deficiency. If you are tired, breathless, pale or
  have heavy periods, your unremarkable nails are not reassurance.
• Spoon nails are not proof of iron deficiency either. The listed causes also include
  hereditary and congenital forms, lichen planus, psoriasis, endocrine disorders, Plummer-Vinson syndrome,
  trauma, and occupational exposure to petroleum products. And in newborns it is
  a normal variant in 33% of cases, usually on the big toe, regressing on its own after
  about age nine.

So the spoon shape is a reason to get a blood test, not a reason to buy iron. The recommended workup is a
full blood count plus an iron panel if anaemia is present.

Ridges that run across: Beau’s lines

These are different in kind, not degree. A transverse groove records a moment when nail production
paused:

Transverse groves in the nail plate occur at a time of trauma or severe systemic illness, due
to a temporary reduction in activity of the nail matrix.

The AAD says the same thing in plainer language: something slowed or stopped your nails from growing for
a while.

The useful property of Beau’s lines is that they are datable. Fingernails grow at roughly 3 mm a month,
so a groove sitting a centimetre from the cuticle records an event about three or four months ago. People
often find that it lines up with a fever, a hospital admission, a course of chemotherapy or a period of
severe illness they had half forgotten.

The associations listed include febrile and infectious disease, dermatologic disease, treatment with
anti-mitotic drugs, myocardial infarction and surgical operations. Notice what is missing from that list.
Not one nutrient.

White spots are not a calcium deficiency

This one deserves stating flatly because the myth is close to universal. Small white marks in the nail
plate, punctate leukonychia, are in the overwhelming majority of cases the result of
minor trauma to the nail matrix weeks earlier: knocks, aggressive manicures, pushing back
cuticles. They grow out with the nail.

Calcium does not deposit in the nail plate in a way that produces spots, and no authoritative source
lists calcium deficiency as a cause. If you have been taking calcium for white spots, you have been treating
an old knock.

Brittle, splitting nails

Nail brittleness affects up to 20% of the population, especially women over 50. Most
cases are idiopathic, meaning no cause is identified, with secondary cases arising from inflammatory
disorders, infections, systemic disease, medication, trauma and altered nail hydration.

Nutrition is acknowledged but placed carefully: a severe deficiency of vitamins, trace elements
and amino acids may result in nail fragility and thinning. Severe is doing the work in that sentence, and
the review treats nutritional causes as secondary rather than the main driver.

What about biotin?

This is the supplement the entire nail aisle is built on, so it is worth quoting both halves of what the
review says.

The favourable half: several studies have demonstrated an improvement in firmness and hardness of the
fingernails in patients receiving biotin supplementation, and a dosage of 5 to 10 mg a day for 3 to
6 months is usually recommended.

The half that rarely makes it onto a product page:

However, these studies were small, not well controlled, and one study was retrospective,
survey based.

And a practical warning that matters more than most people realise: high biotin intake interferes
with laboratory tests. This is not theoretical. High-dose biotin can distort thyroid function tests
and cardiac troponin assays, which means it can produce a falsely reassuring or falsely alarming result in
tests used to diagnose thyroid disease and heart attacks. If you take it, tell whoever draws your blood.

The rule that decides whether this is systemic

One sentence from the systemic-disease literature does more sorting than any list of nutrients:

Changes that affect all 20 nails are likely to be due to an underlying systemic illness, drug
or genetic mutation.

So count. A ridge on one thumb is a knock to that thumb’s matrix. The same change on every finger and
every toe is your body doing something, and that is the version worth taking to a doctor.

Frequently Asked Questions

What deficiency causes ridges in your nails?

Lengthwise ridges are not a deficiency sign. They are the most common age-related nail change, present in
85% of patients in a study of 100 people aged 60 to 101, and ageing is described as the most common cause of
the longitudinal ridging known as onychorrhexis. The American Academy of Dermatology describes lines running
the length of a nail as common and usually nothing to worry about. The nail change that does track a
deficiency is a different shape: koilonychia, where the nail becomes thin and concave like a spoon, which is
classically associated with iron deficiency anaemia.

What do spoon-shaped nails mean?

Most often iron deficiency, but it is worth knowing how weak the sign is in the other direction.
Koilonychia is found in only 5.4% of patients with iron deficiency anaemia, so most iron-deficient people
have normal-looking nails. Other listed causes include hereditary and congenital forms, lichen planus,
psoriasis, endocrine disorders, Plummer-Vinson syndrome, trauma and occupational petroleum exposure, and in
newborns it is a normal variant in 33% of cases that usually regresses after about age nine. The correct
response is a full blood count and an iron panel, not a supplement.

Do white spots on nails mean a calcium deficiency?

No. Punctate leukonychia is in the great majority of cases caused by minor trauma to the nail matrix weeks
before the spot appeared, from knocks, manicures or cuticle pushing, and it grows out with the nail. Calcium
deficiency is not listed as a cause in authoritative sources. This is one of the most durable pieces of
health folklore there is, and correcting it is free.

What causes ridges that run across the nail?

Those are Beau’s lines, and they record a pause in nail production caused by trauma or severe systemic
illness, described as a temporary reduction in activity of the nail matrix. Associated events include fever
and infection, dermatologic disease, anti-mitotic drugs such as chemotherapy, myocardial infarction and
surgery. Because fingernails grow at roughly 3 mm a month, the distance of the groove from the cuticle dates
the event. No nutrient appears in the list of causes.

Does biotin actually work for nails?

The honest answer is: possibly, on weak evidence. A review notes several studies showing improved firmness
and hardness with biotin, at a usual dose of 5 to 10 mg daily for 3 to 6 months, and then states plainly that
these studies were small, not well controlled, and one was retrospective and survey based. There is also a
practical hazard worth knowing: high biotin intake interferes with laboratory tests, including thyroid
function and cardiac troponin assays, so anyone taking it should say so before blood is drawn.

When should iron supplements be used for nails?

When a blood test says so. The brittle-nail review attaches a specific threshold: iron supplementation
plus vitamin C may be very effective when ferritin is below 10 ng/ml. For diagnosed iron deficiency causing
koilonychia, repletion with 150 to 200 mg of elemental iron usually returns the nail to normal within 4 to 6
months, which is about the time a fingernail takes to grow out. None of that is a case for taking iron
without a measurement, because unnecessary iron causes side effects and is harmful in undiagnosed iron
overload.

Are brittle, splitting nails a deficiency?

Usually not. Brittleness affects up to 20% of the population, particularly women over 50, and most cases
are idiopathic. Secondary causes listed are inflammatory disorders, infections, systemic disease,
medications, trauma and altered nail hydration. Nutrition appears only as severe deficiency of
vitamins, trace elements and amino acids, and the review treats nutritional causes as secondary rather than
the main driver.

How do I know if my nail change is serious?

Count how many nails are affected. The systemic-disease literature states that changes affecting all 20
nails are likely due to an underlying systemic illness, drug or genetic mutation. A change on one nail
usually points at something that happened to that nail. The same change everywhere is the version worth
investigating. Any single dark streak under a nail, or a change that is spreading, should be looked at
regardless of this rule.

Will taking a multivitamin fix my ridges?

Not if they run lengthwise, because there is no deficiency to correct. That is the practical consequence
of the 85% figure: something that common in older nails is a structural property of ageing tissue, and no
nutrient reverses it. Money spent on this is better spent on a ferritin test if you have other reasons to
suspect iron deficiency, since that is the one nutritional finding on this page with a documented nail effect
and a documented reversal.

Sources

• Study of nail changes and nail disorders in the elderly. 100 patients, youngest 60 and oldest 101 years.
  Among nail surface changes, prominent longitudinal ridges were the commonest at 85%, followed by rough nails
  in 33%, transverse ridges in 23% and lamellar split in 15% of cases; classified among senile changes of
  ageing. Checked August 2026 —
  PMC3221241
• Spoon Nails (koilonychia), StatPearls. Thin, brittle, concave nail dystrophy with the plate centrally
  depressed and everted laterally; koilonychia in 5.4% of patients with iron deficiency anaemia; a normal
  variant in 33% of newborns, especially the big toe, regressing spontaneously after about age nine; aetiology
  including hereditary and congenital forms, iron deficiency anaemia from malnutrition, worms, coeliac disease,
  gastrointestinal blood loss or malignancy, lichen planus, psoriasis, endocrine disorders, Plummer-Vinson
  syndrome, trauma and occupational petroleum exposure; evaluation with full blood count and iron panel;
  treatment with 150 to 200 mg elemental iron, with the nail abnormality usually returning to normal within 4
  to 6 months of iron repletion. Checked August 2026 —
  StatPearls NBK559311
• Nails in systemic disease. Koilonychia classically associated with iron deficiency anaemia and shown to
  improve with iron supplementation; transverse grooves in the nail plate occur at a time of trauma or severe
  systemic illness, due to a temporary reduction in activity of the nail matrix; changes that affect all 20
  nails are likely to be due to an underlying systemic illness, drug or genetic mutation. Checked August 2026
  —
  PMC8140692
• Pathogenesis, clinical signs and treatment recommendations in brittle nails: a review. Nail plate
  brittleness affects up to 20% of the population, especially women over 50; idiopathic and secondary forms,
  the latter due to inflammatory disorders, infections, systemic diseases, medications, trauma and altered
  nail hydration; iron supplementation plus vitamin C may be very effective when ferritin levels are below 10
  ng/ml; several studies have demonstrated improvement of firmness and hardness of fingernails with biotin at a
  usual dosage of 5 to 10 mg a day for 3 to 6 months, however these studies were small, not well controlled,
  and one study was retrospective and survey based; high biotin intake can interfere with laboratory tests.
  Checked August 2026 —
  PMC6994568
• American Academy of Dermatology, 12 nail changes a dermatologist should examine. Lines that run the
  length of a nail are common and usually nothing to worry about; deep grooves that run the width of the nail
  indicate something slowed or stopped nail growth for a while; thin fingernails that dip down in the middle
  and look like spoons may indicate insufficient iron. Checked August 2026 —
  AAD

All percentages on this page are quoted from the named studies and
were checked against the published sources in August 2026. Where a figure cuts against the usual advice, as
the 5.4% koilonychia rate does, it is given rather than omitted. This page summarises published dermatology
literature, cannot see your nails, and is not a diagnosis.