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Koilonychia affects the shape of nails. The nails start to curve like a spoon. Possible causes include nutritional deficiencies and autoimmune conditions.

In some cases, resolving the problems means the nails will start to grow as usual again.

Find out more here about what causes koilonychia and what to do about it.

Koilonychia is often a sign of another condition. Many different factors can trigger it, but sometimes, there is no clear cause.

Below are some of the possible causes.

Nutrition deficiency

spooning of the nails due to koilonychia. Image credit: CHeitz, 2014.Share on Pinterest
Changes to the nails may signify a health condition.
Image credit: CHeitz, 2014.

Iron deficiency is the most frequent cause of koilonychia. Iron deficiency anemia is the world’s most common nutritional deficiency disease. It most commonly affects children and women of childbearing age.

The following health problems can lead to an iron deficiency:

People who do not consume enough folate, protein, and vitamin C can also develop an iron deficiency.

People with Plummer-Vinson syndrome may have koilonychia. This condition can affect those with long term iron deficiency.

What are the other symptoms of iron deficiency? Find out here.

Autoimmune conditions

Koilonychia can occur with:

In psoriasis, a problem with the immune system can lead to nail and skin changes.

Learn more about nail psoriasis.

Environmental exposures

Scientists say there may be links between koilonychia and products that contain petroleum.

Some people, such as hairstylists, may frequently work with products that contain petroleum. This could increase their risk of koilonychia.

People that live at high elevations may also have a higher risk of developing koilonychia.

The air at higher altitudes contains less oxygen than it does at lower levels. When oxygen levels are low, the body produces extra red blood cells. It needs iron to do this, and this can leave the body short of iron.

In 2003, researchers carried out a study among people living at high altitudes in the Ladakh region of India. Almost half of the participants had koilonychia, and it especially affected those in middle age.

In addition to the altitude, the traditional diet of those living in this region is low in iron. This further increases their risk of koilonychia.

Genetic factors

Koilonychia can occur as a result of some genetic conditions.

These include:

Other conditions

Koilonychia has links with the following conditions:

What does it mean if there are ridges in your nails? Find out here.

Flat nails can be an early sign of koilonychia. Nails tend to flatten before developing the characteristic concave shape.

Most nails curve down and are convex. When the nails become concave, people sometimes describe it as being able to hold a drop of water on the top of their nail.

The changes are often easier to spot on fingernails rather than toenails.

People who have a higher risk of koilonychia include:

  • older people
  • those who have low blood flow to their fingers and toes
  • women during menstruation
  • anyone with a higher risk of iron deficiency
  • people with lupus
  • people with an eating disorder or malnutrition
  • some people who follow a vegetarian or vegan diet
  • those who work with petroleum-based solvents

The health implications of koilonychia may depend partly on the age of the person who has it.

In adults, koilonychia may be a sign of a health condition that needs medical attention.

In infants, koilonychia is common. In 2016, an observational study involving 52 newborns found that 32.7% of the infants had koilonychia.

In infants, the nail shape usually becomes regular in time. However, parents or caregivers who have concerns should speak to a health professional, as concave nails in infants could also indicate a genetic disorder.

Anyone who notices changes in their nail shape should seek medical advice, as they may need treatment.

Treatment will depend on the cause of koilonychia. Some causes will respond to dietary changes. Consuming enough iron in the diet can also help prevent unwanted nail changes.

A doctor will likely take a full medical history, perform a physical exam, and may order blood tests.

In some cases, iron deficiency resolves with dietary changes. A person may need to eat more food that contains iron, or they may need iron supplements.

The Office of Dietary Supplements (ODS) recommend that adults should get the following amounts of iron from their diet each day:

  • Adult males: 8 milligrams (mg)
  • Adult females: 18 mg

Recommendations for children will depend on the age and sex of the child.

The ODS add that vegetarians should eat 1.8 times more iron than those who eat meat. This is because iron from plant based foods is harder for the body to absorb than iron from animal products. Combining plant based sources of iron with vitamin C rich foods, such as citrus fruits, can help increase iron absorption.

Good sources of iron include:

  • fortified breakfast cereals, which may contain 100% of the daily requirement in just one serving
  • other fortified foods, such as bread and enriched rice
  • dark chocolate
  • beans, lentils, and chickpeas
  • beef, especially beef liver
  • tofu
  • leafy greens
  • baked potato
  • cashews

People can check the ingredients of premade foods by reading the label.

If the person has genetic factors that result in nail changes, a doctor will advise on the next step.

Get some tips on how to strengthen the nails.

Koilonychia is just one type of nail problem.

Other types include fungal infections, nail psoriasis, and ridged nails. These can all be signs of another condition or problem.

Tips for taking care of nails when problems occur include:

  • wearing rubber gloves when washing up or using cleaning products
  • using a soft nail brush to keep the nails clean
  • applying hand cream to nails to moisturize them
  • trimming the nails after a bath or shower, when they are soft
  • keeping the nails short and trimming toenails straight across the top
  • clipping back broken nails to where they join the skin, to reduce the risk of further splitting
  • choosing footwear that does not cramp the toes and nails

If redness, inflammation, or other changes occur around the nails, people should seek medical advice.

Koilonychia often stems from an iron deficiency in the diet, and it may respond to dietary changes. If the underlying reason is not a dietary one, a doctor may recommend medical treatment, depending on the cause. Some conditions interfere with the amount of iron and oxygen the red blood cells hold.

Dietary changes can often help nails recover their usual shape, but this can take time.

According to one report, fingernails take around 6 months to regrow fully, while toenails take 12–18 months.

Can you make your nails grow faster? Find out here.

For people with an iron deficiency, a doctor may prescribe supplements. There is a selection of iron supplements available for purchase online.

People should always speak to their doctor before using supplements, as some supplements can have adverse effects on an individual. A doctor can also advise the person on how much to take.



Getting a manicure will help keep nails clean, trimmed, and filed, but people should avoid:

  • using polish or polish remover containing acetone
  • biting the nails
  • false nails

I recommend avoiding nail polish and remover until your nails have returned to normal.

Debra Rose Wilson, Ph.D., MSN, R.N., IBCLC, AHN-BC, CHT Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

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