Fingernails that are yellow can be an indication of a medical disorder in some cases. These include liver disease, lung disease, diabetes, kidney disease, and nutritional deficiencies, most notably iron and zinc.

Although most cases of yellow nails are not caused by an internal disorder, underlying medical problems should be ruled out if your nails have suddenly changed in color.

Simple blood tests can generally rule out most causes of yellow fingernails.

Cause of yellow fingernails: Nail fungus

One of the early signs of a nail fungal infection is a yellow or brown discoloration of the fingernails.

Cause of yellow fingernails: Smoking