What causes spoon-shaped fingernails?

Fingernails are fun. You can paint them, shape them, and fake them, and they're a great way to reveal your personality in a completely subtle and appropriate way. We think nails are so much fun that we often forget that they are actually there for another very important reason. "Your nails are a very good reflection of your health," claims dermatologist Christine Poblete-Lopez, MD of the Cleveland Clinic Hospital. "Many things can occur in the nails that can signify systemic or skin problems."

But what is the meaning behind spoon-shaped fingernails? And, more importantly, what causes them to become spoon-shaped?

Medically speaking, spoon-shaped (or concaved) nails are referred to as koilonychia. According to medical science journal The Permanente Journal, koilonychia is an abnormal, concave appearance of the fingernail that can indicate anemia or a significant deficiency of iron, which must be professionally diagnosed to determine the root cause. The American Academy of Dermatology lists poor nutrition, stomach problems, and gluten intolerance as possible causes of anemia.

How to treat spoon-shaped nails

Spoon-shaped nails look exactly as they sound — they almost turn inside out to mimic the shape of a spoon. Healthline notes that spoon-shaped fingernails become thin and turn up on the edges, and can even lift out of the nail bed. 

As the cause of spoon-shaped nails differs on a case by case basis, treatment does vary. However, as stated by the U.K.'s National Health System (NHS), most cases of iron deficiency (which is a common cause of this nail problem) are treated with diet changes and iron supplements. However, a full workup might be a good idea if there is no obvious reason you're anemic in the first place. 

To avoid an iron deficiency, the NHS suggests that you increase your consumption of leafy greens, meat, legumes, and fortified cereals, and cut back on tea, coffee, and milk, as these drinks may make it harder for your body to absorb iron.

Essentially, if your nails noticeably change shape or texture, you should head to your doctor to get checked out.