What a healthy nail generally looks like
A smooth surface with a light pink tint from the blood vessels underneath, firmness combined with a reasonable amount of flexibility, and resistance to easy breaking are generally described as the hallmarks of a healthy nail, though natural thickness and tone vary from person to person.
White spots on the nail
Often mistakenly blamed on calcium or nutrient deficiency, white spots are usually just the trace of a minor bump or pressure the nail experienced earlier as it was growing. They typically move upward and disappear as the nail grows out, and are only worth checking on if they appear repeatedly and widely or come with other symptoms.
Vertical ridges
Fine vertical lines that become more noticeable with age are a commonly described, largely harmless change, generally linked to slightly less uniform cell activity in the nail matrix as it ages. If ridges suddenly become very pronounced or come with a color change, it is worth looking into other causes.
Horizontal grooves (Beau's lines)
These horizontal grooves mark a point where nail growth temporarily paused, sometimes following a high fever, major stress, or localized injury. They are described as a trace of cell production in the nail root slowing or stopping and then resuming, and they usually move toward the tip and disappear as the nail keeps growing.
Spoon-shaped nails (koilonychia)
This is a shape where the nail tip curves upward, leaving the center concave. Some sources associate it with iron deficiency, though the exact cause varies from person to person. If your nail shape has changed noticeably, treat this information as a reference only and see a doctor to confirm the actual cause.
Clubbing: a rounded bulge at the fingertip
Clubbing describes the fingertip rounding and bulging as the angle where the nail meets the finger increases. It tends to progress slowly, which makes it hard to notice on your own. If the base of the nail feels softer than usual to the touch, or a fingertip looks unusually round, it is safer to get it checked by a doctor than to self-diagnose.
When a nail turns yellow or thickens
Causes range from temporary staining left by dark nail polish pigment to fungal infection. Yellowing from dark polish is usually superficial and fades over time, especially with a base coat, while yellowing combined with thickening or crumbling may point to a fungal infection or another cause worth investigating.
When it is time to see a doctor
If a clear shape change appears over a short period, if there is pain or bleeding, or if a change persists for a long time, do not rely on this page alone and see a dermatologist or physician. This article is reference information about commonly observed nail changes and is not a substitute for diagnosing or ruling out any specific condition.