White nails can be indicative of hepatitis and other liver diseases, while nails that are half white and half pink can be a sign of kidney disease. Cracked nails, yellowish nails, blue nails, nail beds with altered colors, and red or dark lines through the nail all can indicate disease, as can clubbing around the nails.
Yellowish nails that have a slight blush color at their base can indicate diabetes. Thick, yellow nails that are slow to grow may indicate that the person has a lung disease such as emphysema. Inverted nails or clubbing around the nails, which is characterized by a painless increase in the tissues around the ends of the fingers, can also be indicators of lung disease. Dry, brittle nails may be indicative of thyroid problems.
Red nail beds can signal heart disease, while pale or white nail beds may suggest anemia. Irregular red lines at the nail fold's base can be precursors to connective tissue diseases and lupus, while pitting or rippling of the surface of the nail can indicate inflammatory arthritis or psoriasis. Dark lines beneath the nail can be a sign of melanoma. A bluish tint to the nails can be a sign that the body is not getting a sufficient supply of oxygen.