Spoon-Shaped Nails (Koilonychia)
Koilonychia nails are abnormally thin and flat and often curve at a severe enough angle to hold liquid in your nail.
Spoon-shaped nails have connections to iron levels in your body. Too much iron (hemochromatosis) causes this condition. Too little iron (iron deficiency) can also cause spoon shaped nails due to a lower red blood cell count.
In addition, Raynaud’s disease is known to affect the blood supply to your fingers and toes and is another cause of nail spooning.