Quite A bit
Most commonly, when a physician looks at your finger nails they are looking for characteristics such as clubbing, pitting of the nail, and splinter hemorrhages.
These signs are indicative of other conditions such as heart problems
and lung problems. You can also get an idea about nutritional status. Melanoma
can show up under nails, and psoriasis
can affect nails.
Answer assisted by Garrett Caldwell, Medical Student