Your nails are a surprisingly useful window into what’s happening inside your body. Changes in color, shape, texture, and growth patterns can reflect everything from nutritional deficiencies to heart disease. Some of these changes are completely harmless, while others are worth paying attention to. Here’s what to look for and what it actually means.
Vertical Ridges Are Usually Normal
If you’ve noticed faint lines running from your cuticle to the tip of your nail, you can probably relax. Lengthwise ridges are one of the most common nail changes associated with aging. As you get older, nails grow more slowly and may become duller, more brittle, and slightly yellowed. The tips may fragment more easily. These are all normal parts of aging, not signs of disease.
That said, not every ridge is harmless. Horizontal grooves that run across the nail, called Beau’s lines, tell a different story. These form when nail growth temporarily stops due to a significant stress on the body, such as a severe infection, high fever, major surgery, or extreme emotional stress. Since fingernails grow roughly 3 millimeters per month, you can actually estimate when the disruption happened by measuring how far the groove is from your cuticle. A line halfway up the nail, for instance, points to something that happened about two to three months ago.
What Nail Color Changes Can Mean
Color is one of the most telling features of your nails. Healthy nails are slightly pink with a visible half-moon shape (the lighter crescent near the cuticle). When that color shifts dramatically, it can signal an internal problem.
One of the most well-documented examples is a condition called Terry’s nails, where nearly the entire nail turns white and opaque, like frosted glass, except for a thin brown or pink band at the tip. The half-moon shape disappears entirely. In the 1950s, a physician named Richard Terry found that more than 8 out of 10 people with severe liver scarring (cirrhosis) also had these white nails. Terry’s nails can also appear with kidney disease, heart failure, and diabetes, though liver disease remains the strongest association.
Pale nail beds, where the pink color fades noticeably, often point to anemia or low iron levels. And nails that turn white in specific horizontal bands, called Muehrcke’s lines, are linked to low protein levels in the blood. These bands are unusual because they’re actually in the nail bed, not the nail itself, so they temporarily disappear when you press on the nail.
Yellowed, thickened nails are most commonly caused by fungal infections. But when all the nails slowly turn yellow, thicken, and nearly stop growing, it may indicate yellow nail syndrome. This rare condition involves a triad of yellow nails, swelling in the limbs from fluid buildup, and lung problems like chronic cough or fluid around the lungs. The underlying cause appears to be dysfunction in the lymphatic system.
Shape Changes That Signal Deeper Problems
The shape of your nails can change in ways that reflect serious systemic conditions. Two changes in particular are worth knowing about: clubbing and spooning.
Clubbing is when the fingertips enlarge and the nails curve downward around them, resembling the round end of a drumstick. The angle between the nail and the cuticle area, normally sharp, softens and eventually bulges outward. This change develops gradually and often goes unnoticed for months. Clubbing is strongly associated with lung diseases, including lung cancer, pulmonary fibrosis, bronchiectasis, and cystic fibrosis. It also appears in congenital heart disease and heart infections (endocarditis). The mechanism isn’t fully understood, but it may involve platelet clumps that bypass the lungs and release growth factors at the fingertips, causing tissue to swell.
Spoon nails are the opposite: the nail thins out and curves upward at the edges, creating a concave shape that could hold a drop of water. The most common cause is iron deficiency anemia. If your nails are spooning and you also feel unusually tired, short of breath, or dizzy, low iron is a likely culprit. Spoon nails can also show up with thyroid problems, lupus, Raynaud’s phenomenon, and, less commonly, diabetes. Vitamin B deficiency is another nutritional cause.
Pitting, Crumbling, and Lifting
Small dents or pits scattered across the nail surface are a hallmark of psoriasis, even in people who don’t have obvious skin plaques elsewhere. These pits range from pinpoint-sized (about 0.4 millimeters) to crayon-tip-sized (about 2 millimeters), and you might have just one or two, or more than ten per nail. Nail psoriasis can also cause the nail to crumble, thicken, or separate from the nail bed.
Nail pitting also appears in people with alopecia areata (an autoimmune condition that causes hair loss) and eczema, though the pitting patterns tend to differ. In psoriasis, the pits are typically irregular and scattered, while other conditions may produce more uniform, orderly pits.
Tiny Lines Under the Nail
Splinter hemorrhages look exactly like what they sound like: thin, dark reddish-brown lines running vertically under the nail, resembling tiny splinters. Most of the time, they come from minor trauma. If you work with your hands, play sports, or even do a lot of housework, small impacts can rupture tiny blood vessels under the nail.
When splinter hemorrhages appear on multiple nails without obvious injury, they can indicate something more serious. They’re one of the peripheral signs of infective endocarditis, an infection of the heart valves. However, they aren’t particularly reliable on their own. In suspected endocarditis cases, splinter hemorrhages show up in only about 26% of confirmed patients. They also appear in vasculitis, connective tissue disorders, and drug reactions. So a single splinter line after a weekend of gardening is nothing to worry about, but unexplained lines on several fingers, especially with fever or fatigue, deserve medical attention.
Dark Streaks and When to Take Them Seriously
A dark brown or black streak running the length of a nail is common and usually benign in people with darker skin tones, where it results from normal pigment activation. But a new or changing dark band deserves a closer look, because melanoma can develop under the nail.
Dermatologists use a set of warning signs to evaluate these streaks. A band wider than 3 millimeters with uneven color or irregular borders is concerning. One of the most important red flags is when the dark pigment extends beyond the nail itself onto the surrounding skin at the cuticle or sides of the nail, known as Hutchinson’s sign. Subungual melanoma most commonly affects the thumb, big toe, or index finger, and it’s more frequently diagnosed in people over 50. If you notice a new dark streak that is widening, darkening, or spreading to the skin around the nail, get it evaluated promptly.
Nutritional Deficiencies Beyond Iron
Iron gets the most attention when it comes to nail health, but several other nutritional gaps leave visible traces. Zinc deficiency can cause white horizontal bands across the nails, brittleness, and Beau’s lines. Calcium deficiency is linked to soft, fragile nails with white spots or bands. Magnesium deficiency tends to produce nails that are soft and flaky, prone to splitting and peeling. Even selenium deficiency has a nail signature: the nails may turn white.
Protein deficiency affects nails in multiple ways. In severe cases, nails become soft, thin, and slow-growing. Muehrcke’s lines, those paired white bands mentioned earlier, are specifically tied to low albumin (the main protein in blood) and can appear with malnutrition, kidney disease that causes protein loss, or liver disease that impairs protein production.
Brittle nails that crack, peel, or split easily are one of the most common complaints, and they’re often chalked up to biotin deficiency. While biotin supplementation does help some people with brittle nails, frequent hand washing, nail polish remover, and simple dehydration are far more common causes. Before assuming a deficiency, consider whether your nails are regularly exposed to water and chemicals.
One Nail vs. All Nails
A useful general rule: changes affecting a single nail are more likely caused by local trauma, infection, or, rarely, a tumor under the nail. Changes appearing across most or all nails are more likely to reflect a systemic condition, whether that’s a nutritional deficiency, organ disease, or autoimmune disorder. The speed of change matters too. A nail abnormality that develops over weeks to months is more concerning than one that’s been present, unchanged, for years.
Your nails grow slowly enough that they effectively record several months of your body’s internal history at any given time. Paying attention to new or evolving changes, rather than features that have always been there, is the most practical way to use your nails as a health signal.