Spoon nails are a nail deformity where the center of the nail dips inward while the edges flare upward, creating a concave, scoop-like shape. The medical term is koilonychia, from the Greek word for “hollow.” The indentation can become deep enough to hold a drop of water on the nail surface, which is actually one way the condition is identified. While spoon nails are most commonly linked to iron deficiency, they can also result from chemical exposure, skin conditions, or other underlying health issues.
How to Recognize Spoon Nails
Spoon nails don’t usually appear overnight. In many people, the first sign is that the nails become unusually flat, losing their normal gentle curve. Over time, the center of the nail plate gradually sinks inward while the sides rise, creating that characteristic spoon or saucer shape. The nails also tend to become thin and brittle, making them more prone to chipping or cracking.
The change is easiest to spot when you look at the nail from the side rather than straight on. A healthy nail has a slight convex arc. A spoon nail curves the opposite way. One simple test: place a drop of water on the nail. On a normal nail, the water rolls off. On a spoon nail, the water pools in the depression and stays put. The condition can affect fingernails, toenails, or both, and it may show up on just one nail or several at once.
Iron Deficiency Is the Most Common Cause
The single most frequent reason adults develop spoon nails is low iron levels. Iron plays a key role in how your body builds and maintains nail tissue. When iron stores drop too low, the nail plate grows thinner and softer than it should, eventually losing its structural integrity and curving inward. Spoon nails are considered one of the physical signs clinicians look for alongside other markers of iron deficiency, such as pale skin, cracked corners of the mouth, and hair thinning.
Iron deficiency doesn’t always mean full-blown anemia. Your iron stores can be depleted well before your blood counts drop low enough to qualify as anemia, and nail changes can begin during that earlier stage. Heavy menstrual periods, pregnancy, poor dietary iron intake, and conditions that reduce iron absorption in the gut (like celiac disease) are all common pathways to deficiency.
When iron deficiency is the cause, oral iron supplements are the standard first step. Iron salts taken once daily on an empty stomach are typically recommended. Some people find that taking iron every other day reduces stomach upset while still being effective. If oral supplements aren’t tolerated or don’t work, intravenous iron is an alternative. Once iron levels are restored, the nail gradually grows out normally, but since fingernails grow roughly 3 to 4 millimeters per month, it can take several months for the spoon shape to fully disappear.
Other Medical Conditions Linked to Spoon Nails
Iron deficiency gets the most attention, but it’s not the only explanation. Several other conditions can produce the same nail changes. Thyroid disorders, particularly an underactive thyroid, can affect nail growth and structure. Raynaud’s disease, which restricts blood flow to the fingers, can also contribute by starving the nail matrix of adequate circulation. Certain autoimmune conditions and skin disorders like psoriasis or lichen planus sometimes involve nail changes that include spooning.
Hemochromatosis, a condition where the body absorbs too much iron, can paradoxically cause spoon nails as well. This is because excess iron damages tissues, including those that produce nails. The takeaway is that spoon nails signal something is off with nail growth, but the specific cause requires investigation rather than assumption.
Chemical and Occupational Causes
Not all spoon nails have a medical origin. Repeated exposure to harsh chemicals can damage the nail plate directly, producing the same concave shape. This has been documented in cement workers and bricklayers exposed to alkali, cabinetmakers working with organic solvents, and car mechanics regularly handling petroleum-based oils. Hairdressers who frequently apply permanent wave solutions containing ammonium thioglycolate have developed painful fingertips and spooned nails over time, even without any skin rash on the surrounding fingers.
In these cases, the spooning is caused by external chemical damage rather than a nutritional deficiency. It may affect only the nails on the hand used most during work, which can be a helpful clue. Removing the chemical exposure and protecting the hands typically allows the nails to recover as new growth comes in.
Spoon Nails in Babies Are Usually Normal
If you’ve noticed that your infant’s nails look flat or slightly scooped, it’s likely nothing to worry about. A study published in the Journal of the European Academy of Dermatology and Venereology found koilonychia in about 33% of healthy, full-term newborns. In babies, the nail plate is simply thinner and softer than an adult’s, and it hasn’t yet developed the structural rigidity needed for a convex shape. This type of spoon nail resolves on its own as the child grows, typically within the first few years of life, without any treatment.
Getting a Diagnosis
A doctor can often identify spoon nails through a simple visual exam, sometimes using the water drop test to confirm the concavity. The more important step is figuring out why the nails changed shape. Blood work to check iron levels and a complete blood count are standard starting points. Depending on your other symptoms and medical history, additional testing for thyroid function, autoimmune markers, or other conditions may follow.
If only one or two nails are affected, especially on the same hand, your doctor will likely ask about chemical exposures, trauma, or repetitive activities. Spoon nails that appear on multiple fingers across both hands are more suggestive of a systemic issue like iron deficiency or another internal condition. The pattern of involvement is one of the first clues that helps narrow down the cause.
What Recovery Looks Like
Spoon nails are reversible once the underlying cause is addressed. The damaged, concave portion of the nail won’t reshape itself, but new nail growth from the base will come in with a normal curve. Fingernails take roughly 6 months to fully replace themselves, and toenails can take 12 to 18 months, so patience is part of the process. During recovery, keeping nails trimmed short and moisturized helps prevent the thin, brittle edges from catching and tearing. If you’re being treated for iron deficiency, your doctor will likely recheck your levels after a few months to confirm they’ve normalized before expecting the nail changes to resolve.