A white fingernail can indicate a number of different medical issues. If all of the nails are white or partially whitened, it usually means that a systemic problem is occurring. A single fingernail that turns white may indicate an issue with that specific finger. White nails may be all white or partially white, depending on the cause. In a clinical sign known as Terry's nails, for example, the nails are white with an arc of brown coloration at the tip.
One reason that a fingernail might turn white is poor vascularization in the finger. This can be the result of trauma to the finger or nailbed, as for example when a hand is slammed in a door, or it can be caused by diabetes, cardiovascular disease, or other circulatory problems. People with systemic circulatory problems may observe discoloration in all their fingernails.
Another cause is liver or kidney disease. People with advanced cirrhosis often have white fingernails, for example. Anemia can also lead to whitening and paleness in the fingernails, as can malnutrition.
If the fingernails are white, soft, and crumbly, it is a sign of fungal infection. In the early stages of fungal infection, one or more nails may go white before softening. The nails will be lost if the infection is allowed to persist, exposing the delicate nail bed.
In addition to whitening, fingernails can also thicken, distort, develop raised ridges, and exhibit other signs. All of these clinical signs in the fingernails can be useful diagnostic tools for medical professionals. People who notice changes in the color, thickness, texture, or shape of their fingernails should call a healthcare professional to discuss the situation.
The medical professional may determine that a white, ridged, or otherwise abnormal fingernail is a cause for concern, and recommend some diagnostic tests that can be used to learn more about the situation. Sometimes, changes in the fingernails are the first sign of a more serious underlying problem, and it is important to follow a healthcare provider's recommendations about diagnostic testing even if someone feels healthy and fit.
People who regularly paint their nails should try to get into the habit of periodically checking on nail health by removing the nail polish and other products to allow the natural color of the fingernail to show. It is also important to be aware of changes in texture and thickness that may reveal problems in the nail that are hidden by nail polish.