What causes ridges in your fingernails?

Thinning . Thin nails tend to ridge or curve.
No worries. Vertical nail ridges extend from the cuticle to the tip of the nail. Vertical nail ridges often become more numerous or prominent with age, possibly due to variations in cell turnover within the nail. If your fingernails change color or you develop horizontal nail ridges, consult your doctor. These changes could indicate an underlying health condition.