Vertical lines in the fingernails are actually very common. We do not understand exactly why they develop. It may be in part due to genetic factors and, in part, it may be due to manipulation or minor trauma to the nail matrix (the cells under the cuticle that produce new nail). Due to the last theory, I sometimes recommend that people with these lines avoid biting their nails, picking at the cuticles, and getting manicures to see if that makes a difference. However, there is no evidence that vertical lines in the nails represent any serious medical problem, including a deficiency in protein or other nutrients.
Horizontal lines, however, are rarely normal, and do often represent a sign of an underlying medical problem or recent severe stress on the body. Therefore, if you ever develop horizontal lines, or if you notice that the nail is separating from the nail bed and lifting up, these might be issues that your primary care doctor
or a dermatologist
should investigate to see if something needs to be done.
I recommend discussing this issue with your doctor, just to make sure there is not a serious problem. Most likely, all is well. Good luck!