If you have these lines on your nails after 40, it is a clear sign that..

Horizontal lines (Beau’s lines)
These can suggest past illness, significant stress, or chronic conditions such as diabetes or circulation issues.

Vertical ridges
While common with aging, unusually deep or uneven ridges could point to nutritional deficiencies like iron or vitamin B12 shortage.

Dark streaks
Sudden appearance of dark streaks may signal melanoma, a serious skin cancer, and require immediate medical attention.

White lines (Muehrcke’s lines)
These may be linked to liver or kidney problems, or low protein levels.

Bottom line
After age 40, changes in your nails—especially unusual lines—should not be ignored. They can be an early warning from your body, so it’s important to consult a healthcare provider if you notice anything unusual. Your nails might be revealing health issues before other symptoms appear.