What does it mean when you have indents in your fingernails?

On the other hand, horizontal nail ridges may indicate the presence of an underlying illness or medical condition, although this is not always the case. Horizontal nail ridges run from one side of the nail lengthwise across to the other side. One special type of horizontal nail ridge that may indicate underlying illness is called Beau's lines. Beau's lines give horizontal, deeply grooved ridges in the nails which may be slightly darkened in appearance. There are a variety of causes for these distinctive ridges including a previous injury to the nail bed, malnutrition, certain medications, and metabolic disorders such as Diabetes. The ridge which characterizes Beau's lines occurs when growth of the nail is temporarily arrested due to an underlying illness, nutritional or metabolic problem. If you have this type of horizontal nail ridge, see your doctor right away.