You may not pay much attention to your fingernails on a daily basis, but they can actually reveal a great deal about your overall health. Fingernails often reflect changes happening inside the body, and medical professionals have long recognized nail changes as potential indicators of health issues. In fact, nail examination has been used as a diagnostic tool since ancient times. There are hundreds of medical conditions and diseases that may cause visible changes in the nails, making them an important yet often overlooked health signal.

While nail changes are sometimes caused by minor issues such as fungal infections, cosmetic damage, or physical injury, they can also point to more serious underlying problems. Conditions affecting the liver, lungs, heart, thyroid, or immune system may all show early signs through changes in the nails. Learning how to recognize these signs can help you become more aware of your body and know when it may be time to seek medical advice.

The Half Moons at the Base of Your Nails

Healthy fingernails typically appear pink, with small crescent-shaped areas near the base known as lunulae, or “half moons.” These half moons are usually white or light pink in color. According to Dr. L. Reed, ND, the presence and visibility of these half moons can be an indicator of thyroid health. Nails missing visible half moons may suggest a weaker thyroid function. Thyroid imbalances can contribute to symptoms such as fatigue, mood changes, depression, thinning hair, weight fluctuations, and other metabolic issues.

Nail Texture and Overall Appearance

Healthy nails are smooth and even, without ridges, grooves, discoloration, or unusual thickening. If you notice changes in the color, shape, texture, or growth pattern of your nails and cannot explain them through injury or external causes, it may be a sign of an underlying health issue. Persistent or unexplained nail changes are a good reason to consult a healthcare professional.

Below are some common nail changes and what they may indicate about your health:

1. Brittle or Crumbly Nails

Brittle nails are often associated with aging, frequent exposure to water, detergents, or nail polish. However, they can also be linked to fungal infections, thyroid disorders, psoriasis, or lichen planus, a condition that causes itchy rashes on the skin or inside the mouth. In rare cases, brittle nails may be connected to reactive arthritis, a painful inflammatory condition.

2. Discolored Nails

Changes in nail color can have many causes. Yellow nails may result from prolonged use of nail polish, but they can also indicate fungal infections, psoriasis, liver conditions such as jaundice, sinus infections, thyroid disorders, lung disease, or lymphedema.

Green-black discoloration often suggests a bacterial infection beneath a loose nail. Bluish or purple nail beds may be a sign of reduced oxygen levels in the blood. Gray nails can sometimes be caused by certain medications, while brown nails may point to thyroid disease or malnutrition. Nails that are white at the base and brown near the tips can be associated with kidney disease, AIDS, or chemotherapy.

White nails may occur with aging but can also indicate fungal infection, anemia, liver cirrhosis, heart failure, kidney disease, diabetes, hyperthyroidism, or nutritional deficiencies.

3. Thickened Nails

Thick nails are most commonly caused by fungal infections, but they can also result from psoriasis or reactive arthritis. Thick, yellowish, slow-growing nails may sometimes be associated with chronic lung conditions.

4. Loose Nails

When nails separate from the nail bed, this may be due to injury, infection, allergic reactions to medications, poor circulation, thyroid disorders, or skin conditions such as psoriasis.

5. Spoon-Shaped Nails (Koilonychia)

Spoon-shaped nails curve inward and may indicate iron-deficiency anemia. They can also be linked to conditions such as hemochromatosis (iron overload), Raynaud’s disease, heart disease, or hypothyroidism.

6. Pitting or Dents in the Nails

Small pits or dents in the nail surface are often associated with psoriasis but may also occur with eczema, reactive arthritis, or autoimmune conditions such as alopecia areata.

7. Grooves Across the Nails (Beau’s Lines)

Deep horizontal grooves across the nails can appear after serious illness, injury, chemotherapy, or high fever. They may also be associated with diabetes, vascular disease, zinc deficiency, or exposure to extreme cold.

8. Nail Clubbing

Nail clubbing occurs when the fingertips and nails curve downward and enlarge. While it can be harmless and hereditary, sudden onset may indicate low oxygen levels in the blood. This can be associated with lung disease, heart disease, inflammatory bowel disease, liver disease, or immune-related conditions.

9. White Lines Across the Nails

Parallel white lines running across the nails may indicate low protein levels in the blood. This can be linked to malnutrition or liver disease and should not be confused with small white spots, which are usually harmless.

10. Dark Vertical Stripes on the Nails

Dark stripes running lengthwise down the nail are common in people with darker skin tones and are often normal. However, when such a stripe appears suddenly on one nail, it may indicate a rare form of skin cancer called subungual melanoma and should be evaluated by a doctor.

11. Red or Brown Streaks Under the Nails

These small streaks, known as splinter hemorrhages, are caused by tiny broken blood vessels and are often harmless. However, if they appear on multiple nails, they may be linked to an underlying medical condition.

Final Thoughts

Your fingernails can offer valuable insights into your overall health. Paying attention to changes in your nails and understanding what they may indicate can help you identify potential health issues early. While nail changes are not always a cause for concern, persistent or unusual signs should never be ignored. By observing your nails regularly, you gain a simple yet effective window into your body’s internal health.