Changes in nail color can offer a clue, but blood tests and clinical assessment are much more reliable ways to evaluate anemia or other medical conditions.
7. Yellow, Thickened, or Crumbling Nails
Yellow nails can develop for many reasons. Some are relatively minor, while others require treatment.
One common cause is a fungal nail infection. The affected nail may become yellowish, thickened, brittle, distorted, or crumbly. Debris may accumulate beneath the nail, and the nail may gradually separate from the nail bed.
Fungal infections are more common in toenails but can affect fingernails as well.
Other possible explanations for yellow discoloration include nail polish staining, smoking-related staining, certain medications, and some skin conditions.
A less common condition called yellow nail syndrome can cause thickened yellow nails alongside other health problems, including respiratory difficulties or swelling caused by lymphatic abnormalities.
However, yellow nails alone do not establish that a person has this syndrome.
Can yellow nails indicate cancer?
Yellow discoloration is not, by itself, a reliable sign of cancer.
Although nail changes can occasionally occur alongside systemic illnesses, it is misleading to treat a yellow nail as proof of a serious internal disease.
The pattern and accompanying symptoms matter.
If the nail is becoming thicker, painful, distorted, or separated from the nail bed, seek medical advice to determine whether an infection or another condition is responsible.
Fungal infections may require treatment lasting several months because nails grow slowly. A clinician may examine a nail sample before recommending a medication.
Avoid using harsh chemicals to try to remove discoloration, and do not share nail clippers or other tools if an infection is suspected.
If several nails turn yellow and the change is accompanied by persistent coughing, breathlessness, or unexplained swelling, a medical assessment is particularly important.
The safest approach is to identify the cause rather than assume that every yellow nail represents the same problem.
8. Spoon-Shaped Nails: A Possible Sign of Iron Deficiency
Some nails become unusually thin and curve inward, creating a shallow depression that resembles the bowl of a spoon.
This appearance is called koilonychia.
Mild changes may be difficult to recognize, but more pronounced spoon-shaped nails can sometimes be associated with iron deficiency or iron-deficiency anemia.
Iron is necessary for producing hemoglobin, the protein in red blood cells that carries oxygen. When iron stores become depleted, the effects can extend beyond fatigue and weakness.
Other possible symptoms of iron deficiency include reduced exercise tolerance, dizziness, headaches, and shortness of breath. Some people have few symptoms until the deficiency becomes more significant.
However, spoon-shaped nails can also occur for other reasons, including repeated exposure to certain substances, local trauma, inherited nail characteristics, or other medical conditions.
What should you do?
If your nails have gradually become spoon-shaped, particularly if several nails are affected, discuss the change with a healthcare professional.
Depending on your history and examination, the clinician may recommend a complete blood count and tests of iron status.
If iron deficiency is confirmed, treatment should address the underlying cause as well as replenishing iron when appropriate.
This distinction matters because iron deficiency can result from insufficient dietary intake, impaired absorption, increased requirements, or blood loss.
In adults, unexplained iron-deficiency anemia may require investigation to identify the source, particularly if there are signs of gastrointestinal bleeding or other concerning symptoms.
Do not assume that changing your diet alone will correct every case, and do not begin high-dose iron treatment without appropriate guidance.
Spoon-shaped nails are not a diagnosis, but they may be a useful reason to look more closely at your health.
9. Nail Changes Associated With Psoriasis and Other Skin Conditions
Nails are connected to the skin, and conditions that affect the skin can also influence nail growth.
Psoriasis is one example. Although it is often recognized by red, scaly patches on the skin, it can also affect the fingernails and toenails.
Nail psoriasis may cause tiny pits in the nail surface, separation of the nail from the nail bed, thickening, discoloration, or crumbling.
Some people experience nail changes before obvious skin symptoms develop. Others already know they have psoriasis and later notice changes in their nails.
Another condition, lichen planus, can affect the nail matrix and sometimes cause longitudinal ridging, thinning, splitting, or other structural changes.
Eczema and repeated inflammation around the nails can also affect their appearance.
These conditions do not mean that nail changes necessarily indicate a dangerous internal disease. However, they may require specific treatment to prevent discomfort or progressive nail damage.
How can you tell whether a nail condition needs treatment?
Look for persistent changes such as pitting, separation, thickening, tenderness, recurring inflammation, or changes affecting several nails.
If you already have a diagnosed skin condition, mention new nail symptoms to your healthcare professional.
Avoid aggressive manicures, artificial nail products, or repeated filing if the nails are damaged or inflamed.
A clinician may recommend treatment aimed at the underlying skin condition. In some cases, tests may be needed to distinguish psoriasis from fungal infection or another cause.
Because several nail disorders look similar, trying multiple over-the-counter treatments without confirming the diagnosis can delay appropriate care.
10. Brittle Nails That Split, Peel, or Break Easily
Brittle nails are another common concern.
Some nails split lengthwise, peel into thin layers, or break before reaching the desired length. This can be frustrating and may lead people to assume that their bodies are lacking important nutrients.
In many cases, brittle nails are associated with environmental exposure and everyday habits rather than a serious illness.
Repeated wetting and drying, frequent handwashing, detergents, solvents, aggressive manicures, nail polish removers, and mechanical trauma can weaken the nail plate.
Aging can also contribute to changes in nail strength and flexibility.
However, persistent brittleness may occasionally be associated with underlying health conditions, including iron deficiency, thyroid disorders, skin diseases, or medication effects.
The key is to consider the broader pattern rather than attributing every broken nail to a single cause.
How can you protect brittle nails?
Wear suitable gloves when handling cleaning products or working with prolonged exposure to water.
Apply a moisturizer to your hands, nails, and surrounding skin after washing. Avoid using your nails as tools to open packages, scrape surfaces, or pry objects apart.
Keep nails at a manageable length and file rough edges gently in one direction when appropriate.
Repeatedly applying artificial nails or removing them aggressively can weaken the nail plate and damage surrounding tissue.
If brittle nails persist despite sensible care, or if the changes occur with fatigue, hair loss, weight changes, or other symptoms, discuss them with a healthcare professional.
A blood test or other investigation may be appropriate depending on your history.
Biotin supplements are heavily promoted for nail strength, but not everyone benefits, and the evidence for routine supplementation is limited. High-dose biotin can also interfere with certain laboratory tests, including some tests used to evaluate thyroid function or heart-related conditions.
Tell your healthcare professional if you take biotin before having blood tests.
11. A Nail That Separates From the Skin Beneath It
When the nail plate lifts away from the nail bed, the area beneath it may appear white, yellowish, or opaque. This is known as onycholysis.