I have ridges and never knew what it meant. @Calathea asked about this in the lunules thread and I found this: (attributed to Naturopathic doctor Tsu-Tsair Chi's book) A person with vague vertical or horizontal ridges need not worry. Such markings are perfectly normal and commonly seen in patients over the age of forty. These ridges, especially if they are on the thumbs, can often be attributed to kidney problems. However, if the vertical or horizontal ridges are blatantly noticeable, then this patient may be suffering from an illness and the ridges are symptoms of the disease. Vertical ridges that cover most of the fingernails refer to kidney, aging(hormone), nerve or respiratory system problems. These ridges are frequently seen in elders, but this does not imply that they are a natural part of the aging process. Proper health care can prevent these ridges from forming. If the vertical ridges appear only on the thumbs then they refer to excretory system conditions. Ridges that are on only the four fingers except for the thumb are due to respiratory problems. An entire nail covered with vertical ridges could be caused by trauma sustained by the patient, either recently or as early as within the last year. If the ridges are very conspicuous, then the patient may be suffering from peripheral blockage, particular yeast or fungus infection, or a hair follicle corneum. A person with vertical lines across the faces of his nail could also suffer from Vitamin A deficiency or a chronic inflammation. If the nails have vertical ridges that can be very easily split down the middle, this could be due to adrenal gland problems. For those under the age of forty, vertical ridges definitely indicate problems as imbalance in the five elements system. These types are usually chronically fatigued, nervous, and suffer neurasthenia. Young people also suffer bronchitis, asthma, or laryngitis. In these people, ridges on the thumb signal spleen and heart problems and may be related to depression. Those on the index finger signal unhappiness in the patient, while middle finger ridges show nervousness and hyperactivity. Vertical ridges on the ring finger signal the possibility that the patient is heartbroken or suffering emotional trauma, while those on the pinky nail show long time stress and the overexertion of energy leading to liver and kidney damage.