Nail symptom: They’re concave enough that a drop of water wouldn’t roll off them.
The technical term: Spoon or scooped nails
The no-big-deal explanation: Nails can take on a hollowed-out look with normal aging.
Why you should get it checked out anyway: Iron disorders like iron-deficiency anemia are the most common cause of spoon or scooped nails, says Dana Stern, MD, a board-certified dermatologist and nail specialist in New York. Your doctor will likely do a blood test to check your ferritin (iron) levels, as it’s possible that your nails would be the first sign of the problem, says Chris Adigun, MD, a fellow of the American Academy of Dermatology and a nail specialist in Chapel Hill, North Carolina. (That doesn’t mean that all cases of anemia cause spoon or scooped nails, though—other symptoms include fatigue, lightheadedness, pale skin and headaches.) Another, less common, possibility is that you’ve got a thyroid issue. Either way, your nails should return to normal once the underlying cause is under control.

Nail symptom: Vertical brown or black bands
The technical term: It depends (see below)
The no-big-deal explanation: Pigmentation in nails is very common, especially in people of color, says Stern. Regardless of your skin color, though, if you’ve had the band for a long time and it hasn’t changed, or you have bands on multiple nails, there’s little reason to worry. Even new bands can be the result of a trauma activating the pigment-producing cells in your nail, like an overly zealous manicure, medications like antibiotics or blood pressure meds, or even pregnancy. It could also be a mole or freckle, though those are more common in children.
Why you should get it checked out anyway: Stern estimates that in less than 3 percent of cases, these bands are actually a melanoma growing in your nail. (All the more reason to remove your nail polish before you get a skin-cancer screening.) Melanomas are more common on the thumb and index finger (experts aren’t sure why) and usually only occur in one nail. If the pigment starts leaching out onto the surrounding skin, that’s a sign that you need to see your doctor now, says Stern, because it means the tumor is growing.

Nail symptom: It looks like someone took a teeny icepick to your nails over and over
The technical term: Pitting
The no-big-deal explanation: Unfortunately, pitted nails are almost always an indication that something more serious is going on.
Why you should get it checked out anyway: Pitting is usually a sign of psoriasis, and nails can be the first place the inflammatory condition, which affects about 7.5 million Americans, shows up. “Psoriasis is the number one underlying health issue that I diagnose based on nails,” says Adigun. People with nail psoriasis are at increased risk of developing psoriatic arthritis, which is why it’s important to get any pitting looked at by a doctor. You might also notice red dots in the lunula (the whitish half-moon at the bottom of your nail) or small brown areas on your nail (these are spots where the nail is about to separate from the nail bed).

Nail symptom: Your nails looks overly curved and bulbous
The technical term: Nail clubbing
The no-big-deal explanation: Oftentimes, nail clubbing occurs in completely healthy people, says Adigun. It can even be hereditary.
Why you should get it checked out anyway: Clubbed nails can be caused by respiratory disease, chronic lung infections or a heart issue, explains Stern, likely because these conditions compromise the blood flow that nails rely on to stay healthy. That’s why your doctor will probably order a cardio-pulmonary workup if you present with nail clubbing. (The other sign, in addition to the nail shape, is a spongy feel if you press down on the nail just above the cuticle.)

Nail symptom: The half-moon is taking up more than half your nail.
The technical term: Terry’s nails
The no-big-deal explanation: Sometimes the half-moon of the nail creeps upward for no obvious or worrisome reason.
Why you should get it checked out anyway: Terry’s nails have been linked to three serious issues: liver disease, congestive heart failure and diabetes. If your half-moon is dominating just about half your nail, it could be Lindsey’s nails instead, which are linked to kidney failure. (Experts aren’t sure why these specific nail issues and health problems are linked.) Of course, these are big-enough issues that your nails are unlikely to be the first problem you notice, says Adigun.

Nail symptom: You’ve got deep, horizontal ridges running across your nails.
The technical term: Beau’s lines
The no-big-deal explanation: Just as your hair can stop growing and start shedding a few months after a stressful event, so can your nails, and the result is these ridges. “I can tell a patient exactly when the stressor happened by measuring the distance from the ridge to the cuticle,” says Adigun. Any illness that puts acute stress on the body can cause them, from a high fever to a hospitalization, and emotional events can trigger them too.
Why you should get it checked out anyway: Since these ridges indicate something was causing you or your body serious worry months ago, they usually aren’t a cause for concern. But if you continue to get ridges even after you think a stressor has passed, it might be a sign that you’re not quite over it, since nails start to grow normally again once the stress had faded.

Nail symptom: They’re yellowish
The technical term: It depends (see below)
The no-big-deal explanation: The most common cause of yellowish nails is nail polish stain, says Adigun. The darker the shade, the more likely it is to leave a mark behind. (You’ll know if you’re dealing with polish-induced yellowness if you can file it away.) It could also be a fungal infection, though those are more common in toenails.
Why you should get it checked out anyway: Sometimes psoriasis can lead to yellow nails. And the most serious, but least common, cause is something called Yellow Nail Syndrome, where the nail grows thicker rather than longer, resulting in a yellowish hue. It’s typically caused by respiratory and lymphatic issues and is more likely to occur in elderly people.

Nail symptom: You’ve got some separation happening.
The technical term: Onycholysis
The no-big-deal explanation: Your manicurist might have gone overboard on cleaning beneath your nails, separating the nail from its nail bed. “Mixing certain medications like tetracycline and doxycycline with UV exposure,” like the kind you’d get from sticking your fingers under a UV light to harden a gel manicure, “can also lead to nail separation,” says Stern.
Why you should get it checked out anyway: It could also be hyperthyroidism. It’s a much less common cause of onycholysis, but it does happen, says Stern, and you’d notice it suddenly and in more than one nail. Remember that separation can indicate psoriasis too.