“Your fingernails and toenails are extensions of your skin. Pay attention to any changes in their appearance and texture—they can provide important clues about your health,” advises Dan Baumgardt, a researcher and lecturer in the University of Bristol’s Department of Physiology, Pharmacology and Neuroscience. Here are a few key points to watch for.
Spoon Nails
Nails on your fingers and toes should have a slight convex curve without any dips or indentations; those depressions can indicate underlying problems. For instance, they may signal koilonychia, a type of nail dystrophy in which the nail becomes concave. In some cases a central indentation forms deep enough to hold a drop of liquid (hence the name “spoon nails”). Typically, nails affected this way look thinner and may become more brittle.
Koilonychia can point to anemia, meaning there aren’t enough red blood cells to carry oxygen to body tissues. It is often linked to iron deficiency, which can stem from poor nutrition.
Mechanics and hairdressers are particularly prone to developing koilonychia because of regular exposure to petroleum-based solvents. Still, there are many possible causes for spoon nails, so consult a doctor if you notice this change.
Discolored Nails
Healthy nail beds should be pink. Changes in color of the nail bed or the nail itself can signal illness.
Yellow nails, for example, may indicate a fungal infection or changes caused by a skin condition like psoriasis.
A change in nail color to white—known as leukonychia—can be a sign of various diseases. For instance, white spots on the nails may indicate heavy metal poisoning from lead or arsenic. That is a significant issue for populations in many countries with contaminated water systems.
If the white color spreads across the entire nail or appears on several nails, the problem is more likely related to a protein deficiency in the blood. That could indicate liver or kidney disease.
Minor white spots on the nails usually point to traumatic injury. If you’ve ever stubbed your toe or pinched your finger, you might have seen the nail turn dark purple, blue, or red. That discoloration is a subungual hematoma—a collection of blood between the nail and its bed following an injury, as reported by Science Alert.
Emergency Nail Tests
In emergency care, doctors often check a patient’s nails to estimate blood oxygen saturation. This measurement is taken with a pulse oximeter, which clips onto a finger and passes light through the fingertip to estimate the oxygen saturation of the blood.
By assessing how much oxygen is entering the bloodstream, clinicians can gauge how well the heart and lungs are functioning.
Another quick test of circulatory function is capillary refill time. The clinician presses on the nail or fingertip for five seconds, causing the skin underneath to turn white. After releasing the pressure, the skin should return to its normal color within two seconds. If it takes longer, the person may be dehydrated, frostbitten, or have poor peripheral perfusion. That means the heart isn’t pumping blood strongly enough, or something is obstructing blood flow to the body’s extremities, possibly due to shock.
Nails can also be pressed to check a patient’s response if they are drowsy or unconscious. That check can be part of assessments used with the Glasgow Coma Scale, which measures responsiveness and level of consciousness.
What to Do If You Notice Something Unusual
This is a brief overview of potential health issues your nails might reveal. If you’re concerned about changes in the color or shape of your nails, consult a doctor. Artificial or painted nails can hide these changes and delay diagnosis, so keep that in mind if you rely on manicures.
