In a healthy individual, one can always find the half-moon shape at the bottom of the nail. It is a part of the matrix and reveals a lot about your health. Missing half-moon in some cases can be due to malnutrition, depression or anemia.

Lunulae that have a blueish tint could suggest Wilson's disease, a rare inherited genetic disorder in which copper accumulates in the liver, brain and other organs. Red lunulae may indicate heart failure, research shows.

Not being able to see a half-moon, or lunula, on the nails may be a sign of a vitamin deficiency, vitiligo, kidney failure, or another health condition. Some people only notice a lunula on their thumbs. Some causes can be serious, so it is best to contact a doctor.