Surprising Things Your Fingernails Can Reveal About Your Health

For example, if the lunula extends almost to the end of the nail, making the majority of the nail white in color except for a narrow band at the top, it could signal cirrhosis, chronic renal failure or congestive heart failure. This condition, called Terry's nails, can also be attributed to aging, according to the Mayo Clinic.

Lunula that have a blueish tint could suggest Wilson's disease, a rare inherited genetic disorder in which copper accumulates in the liver, brain and other organs. Red lunula may indicate heart failure, research shows. And in patients with severe kidney disease, it's not uncommon to see half-and-half nails, where the white from the lunula extends halfway up the nail bed, and the other half of the nail is darker in color, says Richard H. Flowers, M.D., assistant professor of dermatology at the University of Virginia.

2. Changes in nail shape and texture

Pitted nails

An abnormal nail shape and nail surface can also signal a health issue. For example, nails that are dimpled or pitted — “like somebody took a pen and just pressed it in and it made an imprint,” Flowers says — can point to psoriasis, a chronic skin disease. Psoriasis can also cause the nails to loosen and separate from the nail bed, as can thyroid disease.

Spoon nails

Soft nails that look almost as if the center of the nail bed has been scooped out (dubbed spoon nails) can be a sign of an iron issue — either your body isn't getting enough (iron-deficiency anemia) or it's storing too much, a condition known as hemochromatosis, according to the Mayo Clinic.

Clubbed nails

A nail that curves around an enlarged fingertip, known as clubbing, may suggest cardiovascular and pulmonary problems. It can also occur alongside gastrointestinal problems.

3. Lines on the nails

Melanoma

If you notice a dark-colored streak that runs the length of the nail, contact your doctor. It could be melanoma, the deadliest form of skin cancer. While rare, melanomas can appear on or around the fingernail (so be sure to check the skin around your nail, too). And unlike heart disease, kidney disorders and other conditions, melanoma doesn't usually cause other noticeable symptoms, Flowers says — the color of your nail could be your only clue. “So if you get a solitary new band on a nail, you should definitely see a dermatologist about that,” he adds.

Beau's lines

If your nails are decorated with an indented horizontal line, that could be a sign that you experienced a serious illness or sustained an injury or shock to your system that caused the nails to temporarily stop growing. These lines, called Beau’s lines, may also be a marker of uncontrolled diabetes or the result of cancer treatment or exposure to cold temperatures in people with Raynaud’s disease, a rare blood vessel disorder.

4. Changes in color

Nails that have a blue hue can be a warning sign of COVID-19, caused by low levels of oxygen in the blood, Linder says. The Centers for Disease Control and Prevention recommends that anyone who has this symptom seek immediate medical care.

Less dire is a yellow discoloration of the nails. This syndrome can appear in patients with chronic bronchitis and other lung diseases. Fungus, as well, can turn the nails yellow, though this is more common in toenails than fingernails, the Mayo Clinic says. And though a nail fungal infection can happen at any age, older adults are more at risk.

If your nails appear white, it could be Terry’s nails (see above) and reflect an issue with the liver, kidney or heart. It could also be an inherited genetic trait.

Thin and brittle nails may just need some TLC

If your nails are thin and brittle, a thyroid disorder may be to blame, or it may be that they just need more moisture.

“We always tell our patients that just like your skin tends to dry and thin and lose its ability to retain moisture, the nails do the same thing,” Flowers says. And, as with the skin, nails can absorb moisture, which is why he recommends rubbing them with Vaseline when they feel dry. “And that can kind of help prevent some of the cracking and splitting” from normal wear and tear, he says.

Wearing gloves when you do the dishes or clean with chemicals can also prevent nails from becoming brittle. Another way to keep them in top shape is by eating a well-balanced diet.

One thing Flowers doesn’t recommend, however, is the nutritional supplement biotin, which is often touted for its ability to strengthen frail nails. Flowers argues that there's not much evidence to indicate it helps. And taking it in supplement form can “significantly interfere with certain lab tests and cause incorrect results that may go undetected,” the Food and Drug Administration notes in an advisory to the public — including tests that diagnose heart attacks. It’s always best to consult a doctor before adding any new over-the-counter drug or supplement into the mix.

Editor’s note: This story, originally published Aug. 13, 2021, has been updated to include new information.

Rachel Nania writes about health care and health policy for AARP. Previously, she was a reporter and editor for WTOP Radio in Washington, D.C. A recipient of a Gracie Award and a regional Edward R. Murrow Award, she also participated in a dementia fellowship with the National Press Foundation.