My nails are turning yellow. Do you think I have a nail disease?

Possibly. Yellowing discoloration of the toenails can be caused by a fungus, however, it can also occur due to thyroid disorders, B12 or b6 deficiency, aging, or trauma to the nail bed. You should have your physician evaluate the nails and if there is any question a nail culture can be completed to evaluate for a nail fungus.
Possibly. Yellow nails are often a sign of a fungal infection of the nails. Other diseases also can lead to yellow nails though but these are often associated with other medical problems or symptoms. You should have it checked out by a doctor.

Related Questions

Tell me about yellow nail syndrome / twenty-nail disease?

Interesting question. yellow nail syndrome is the yellow discoloration of all 20 nails associated with lymphedema and pleural effusion or fluid in the lungs. Remembert that every nail must be involved. Yellow discoloration can also be seen with fungal infections known as onychomycosis. It's best to see your doctor. And of course with lymphedema and pleural effusions you typcially would be feeling ill. Read more...