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What are spoon nails? 

Spoon nails are exactly what the name suggests: Spoon-shaped nails. It’s an abnormal condition where your nails are centrally curved inwards like the inner surface of a spoon. Koilonychia is the medical name of this condition, pronounced coil-o-nick-e-a. It affects both the fingernails and toenails. 

Anyone can develop koilonychia, including adults, children, and newborns. 

Understanding the causes of spoon nails

Spoon nails have several possible causes, but chronic iron deficiency anemia is the primary cause. 

What causes iron deficiency anemia?

Iron deficiency may result from one of the following: 


Iron deficiency comes from your diet when you’re not eating enough iron-rich foods. Some rich sources of heme iron (iron from animal flesh) include lean meat and seafood. Sources of iron from plants include vegetables, beans, nuts, and fortified grain products. 


You lose iron whenever you bleed. Heavy menstrual periods can cause excessive blood loss. Causes of internal bleeding include:

  • Aspirin and other anti-inflammatory drugs can cause bleeding in the bowel or stomach.

  • Stomach ulcers

  • Bowel polyps

  • Cancer

  • Infection with parasites like hookworms

Your body may not absorb sufficient dietary iron if:

  • You have celiac disease

  • You have Crohn’s disease

  • You’ve had gastric bypass surgery

  • You take too many antacids

Your body needs more iron than usual

This is a common scenario if you’re pregnant or breastfeeding. 

If iron deficiency anemia causes your spoon nails, you may initially experience these symptoms: 

  • General weakness or fatigue more frequent than normal

  • Dizziness

  • Headaches

  • Palpitations

  • Difficulty concentrating

Other symptoms that may develop as the anemia worsens include: 

  • Brittle nails

  • Feeling lightheaded when you stand up

  • Shortness of breath

If you suspect iron deficiency anemia is causing your spoon nails, talk to your doctor for treatment recommendations. 

Other possible causes of spoon nails (besides iron deficiency anemia)

Koilonychia can be secondary to these underlying conditions: 

  • Inflammatory skin diseases, like psoriasis or lichen planus

  • Thyroid issues, like hyperthyroidism or hypothyroidism

  • Diabetes

  • Plummer-Vinson syndrome (difficulty swallowing)

  • Trauma

  • Fungal nail infections

  • Alopecia areata

  • Vascular disorders

  • Genetic disorders

Spoon nails don’t necessarily mean you have an underlying health condition. Iron deficiency is by far the most common cause of spoon nails. 

Trauma is a common cause of spoon nails in children—it may be due to sucking fingers or wearing tight-fitting shoes. The nails usually return to normal afterward. 

Treatment for iron deficiency anemia

Consuming Iron-rich foods or taking supplements may treat iron deficiency anemia. 

Iron supplements

Iron supplements, such as ferrous sulfate, increase the iron supply in your body to compensate for the deficiency. Your healthcare provider will check your iron levels and instruct you on how many pills to take daily and when. Don’t take more than required; it might cause serious health problems. 

You can take the supplements orally. Others may need to take the supplements through an injection (intravenous or intramuscular) if they can’t orally. Your doctor will recommend the correct administration method based on your individual needs. 

If you’re breastfeeding or pregnant, you may require more iron supplements as you usually can’t get enough from a regular food regimen. After six weeks of taking the supplements, your body’s iron levels may return to normal. But when replenishing iron in the bone marrow, you may need to take supplements for six to twelve months. 

Side effects of taking iron supplements may include constipation, vomiting, and nausea. Speak to your doctor if you need to take them while you’re receiving other treatment. For example, iron can affect how well antibiotics work. 

Iron-rich foods

If you don’t want to take supplements, iron-rich foods can be a perfect alternative to treat iron deficiency anemia. They include: 

  • Wholegrain bread

  • Duck eggs

  • Turkey and chicken

  • Liver (the richest iron source of all meats)

  • Fish

  • Dried lentils, beans, and peas

  • Chickpeas and baked beans

  • Oatmeal

  • Greens, such as kale and spinach

  • Dried apricots and prunes

  • Pistachios, peanuts, and cashew nuts

Eating vitamin C can improve your body’s iron absorption. Fruits and vegetables are good sources of vitamin C. They include: 

  • Strawberries

  • Tomatoes

  • Cabbage

  • Kiwi

  • Grapefruits

  • Broccoli

  • Oranges

If you’re iron deficient, talk to your healthcare provider for a personalized treatment plan. Remember, underlying health conditions may cause iron deficiency anemia. In these cases, a doctor will diagnose and recommend the right way to treat the underlying condition. 

How do doctors diagnose koilonychia? 

If you have koilonychia, your nail plates may appear scooped out or centrally curved inwards like the inner surface of a spoon. 

Doctors use a simple clinical procedure called the “water-drop test” to diagnose spoon-shaped nails. They take a syringe and put a few water drops on the affected nails. If you have koilonychia, the droplets will settle on the curved-inwards part of the nail, unlike the normal convex nail plates. 

However, your doctor will need to watch out for false positives when using the water-drop test. Sometimes, people with normal nails may observe a false positive. To overcome this challenge, a small study devised a way of using spherical plastic beads on nail plates to identify spoon nails accurately.¹

Visit a qualified doctor to identify koilonychia. Your healthcare provider will establish the underlying condition and recommend the best possible treatment. 

How to treat spoon-shaped nails

To treat iron deficiency anemia nails, your doctor will identify the underlying condition based on the symptoms you’re experiencing. As mentioned, iron deficiency anemia is the most common cause. But other medical issues like hyperthyroidism, fungal nail infection (onychomycosis), and vascular disorders can cause koilonychia. 

Your doctor will diagnose any underlying disease and recommend personalized treatment. Treatment may involve an iron-rich diet or iron supplements. 

As an infant's nails are usually soft and thin, koilonychia is very common. Your healthcare provider may recommend a wait-and-watch policy instead of treating spoon nails in newborns as many grow out of it. However, close follow-up is necessary to identify any possible underlying condition. 

Can you prevent spoon nails? 

Because of numerous potential causes, there’s no one-fits-all way of preventing spoon-shaped nails. But you can reduce your risk of developing the condition depending on the cause. Since the most common cause is iron deficiency, eating an iron-rich diet may reduce your chances of spoon-shaped nails. 

If you have a medical condition that can cause koilonychia, talking to your doctor about management can minimize the risk of spoon nails. 

Is koilonychia reversible? 

Iron deficiency koilonychia is usually reversible by replenishing the body’s iron supply through supplements or an iron-rich diet. After 4–6 months of iron repletion, the spoon-shaped nails typically return to normal.

However, whether the condition is reversible or not depends on the cause. Some causes, like repetitive occupational trauma or exposure to certain chemicals, may make koilonychia irreversible with time. 

Who is at risk of having spoon nails? 

Anyone can develop koilonychia. There’s no substantial research showing the prevalence of spoon nails within different groups. Additionally, not everyone with an existing medical condition may develop the signs of koilonychia. 

However, some situations may increase the risk of spoon nails. Insufficient iron supply results in iron deficiency anemia—the primary cause of spoon nails. Strict vegetarians and people with poor diets may not get enough dietary iron. 

Your occupation can also put you at risk due to repetitive trauma to the fingers or chemical exposure. 

Are spoon nails always a sign of an underlying medical condition? 

No. Koilonychia may appear after occupational exposure to petroleum products or a physical injury on the fingers. Research has shown that handling ammonium thioglycolate can cause nail spooning over time for hairdressers. 

Rarely, koilonychia is a genetic condition. So spoon nails are not always a symptom of an underlying disease. 

Should you see a doctor if you have koilonychia? 

It’s best to see a doctor if you have spoon nails. While the condition is not always a huge concern, koilonychia may sometimes indicate a serious underlying health condition. 

In most cases, it’s because of iron deficiency. But other serious medical conditions like autoimmune diseases, endocrine disorders, and hemochromatosis might be the underlying disorders in people with spoon-shaped nails. 

A qualified doctor will help identify the cause of koilonychia and recommend the proper treatment for the underlying condition.

The lowdown

If you have koilonychia, your nail plate may centrally curve inwards like the inner surface of a spoon—hence the name “spoon-shaped nail.” The condition has many causes, but iron deficiency anemia is the most common.

Depending on the cause, koilonychia can be reversible. Additionally, having koilonychia does not always mean there’s an underlying condition. Some causes are genetic, while others are because of physical injury to the fingers. 

If you suspect you have koilonychia, seek advice from a healthcare professional.

  1. Bead retention test in koilonychia (2019)

Other sources:

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