Nail Health 101: What Your Nails Are Telling You - and When to See a Doctor

This guide is informational only. It is not a substitute for professional medical advice, diagnosis, or treatment. If you notice a nail change that concerns you, consult a dermatologist or healthcare provider. No nail change should be self-diagnosed.

In this guide:

• What healthy nails actually look like — the baseline every person should know
• The most common nail changes explained: what is usually harmless, what to monitor, and what requires medical attention
• Dark streaks, nail lifting, pitting, clubbing, and discoloration — when each one matters
• The nutrients that support nail strength and growth from the inside
• The daily habits that make the most measurable difference to nail health

Your nails are one of the first places your body shows signs of internal change. Dermatologist Dr. Christine Poblete-Lopez of the Cleveland Clinic states plainly: 'Your nail health is a very good reflection of your overall health. Many things can occur in the nails that can signify systemic or skin problems.' Nail changes can reflect nutritional status, hydration, organ function, autoimmune response, thyroid health, circulation, and more — often before other symptoms appear.

This guide covers what healthy nails look like, what the most common nail changes mean, which changes are worth monitoring, and which require a prompt dermatologist visit. It also covers the nutrition and daily habits with the strongest evidence for supporting nail health.

What Do Healthy Nails Look Like?

A healthy nail has a smooth, slightly curved surface with no horizontal ridges, pitting, or discoloration. The nail plate — the hard part — should appear pinkish, reflecting the nail bed beneath it. The free edge (tip) should be white or off-white. The lunula — the pale crescent at the base of the nail — should be visible, particularly on the thumbs. The surrounding skin should be intact, with no redness, swelling, or lifting.

Healthy nails grow at approximately 3mm per month for fingernails and 1mm per month for toenails. Growth slows in cold weather and with age, and varies significantly between individuals. Healthy nails are firm but have a slight natural flex — complete rigidity or extreme bendiness both indicate a problem.

Surface: Smooth. Faint vertical ridges are normal, especially with age. Any pitting, horizontal ridges, or roughness is worth noting

Color: Pink with a white free edge. Pale pink to light beige on the nail bed. White half-moon (lunula) at base

Texture: Firm, slightly flexible. Smooth surface that reflects light evenly

Cuticle: Intact, flexible, attached to the nail plate base. Not red, swollen, or peeling

Shape: Gently curved following the fingertip. No clubbing, spooning, or pronounced curling

What Do Your Nails Say About Your Health?

Nails are made primarily of keratin — the same protein found in hair and skin. When the body is not functioning optimally or is not receiving adequate nutrition, the nail matrix (where new nail cells form) is one of the first places this is reflected. Because the body prioritizes essential organs over structural proteins like keratin, any systemic stress — nutritional deficiency, illness, medication, or organ dysfunction — tends to show up in nail quality, growth rate, color, and texture.

Not every nail change is a health signal. Many are completely benign — trauma-related white spots, dryness from weather, or simple aging. The skill is knowing which changes to monitor and which require attention. Here are the most commonly encountered nail changes and what they typically indicate:

The three-tier nail change guide — normal variations, changes to monitor for 2–4 weeks, and changes that warrant medical attention.

Vertical Ridges

Usually normal and benign. Faint vertical ridges running from the base to the tip of the nail are extremely common and typically reflect nothing more than the aging process — the nail matrix becomes less efficient at producing perfectly uniform cells over time. They tend to become more pronounced in the 40s and 50s. If they appear suddenly and severely across multiple nails in a younger person, mention them to a doctor, but in most cases they require no action.

Horizontal Ridges (Beau's Lines)

Worth investigating. A horizontal ridge — or indentation running across the nail — is called a Beau's line and indicates a disruption to nail matrix function at a specific point in time. Because the nail matrix continuously produces new cells, a single horizontal ridge represents a single event that temporarily interrupted normal growth. Common causes include high fever, severe illness, major surgery, chemotherapy, significant nutritional deficiency, or extreme physical stress. The ridge grows out with the nail. Multiple simultaneous Beau's lines across all fingernails suggest a systemic event worth discussing with a doctor.

White Spots (Leukonychia)

Almost always harmless. The small white spots most people notice on their nails are called leukonychia and are caused by minor trauma to the nail matrix — a knock, a tight grip, or pressure on the nail base. Because the nail matrix is where new cells are produced, even minor trauma can cause a small disruption that shows up as a white mark several weeks later (the time it takes for the affected cells to grow to where they are visible). These spots grow out with the nail and require no treatment. White discoloration that covers most of the nail — particularly if it has a two-toned appearance with a pink band near the tip — can occasionally indicate liver conditions and is worth showing to a doctor.

Yellow Nails

The most common cause is nail polish staining — not a health concern. Dark polish worn without a base coat can leave a yellowish tint on the nail plate that fades as the nail grows out. If yellowing appears in nails that have not been polished, or if it is accompanied by thickening, crumbling, or detachment of the nail from the bed, a fungal infection (onychomycosis) is the most likely cause. Fungal nail infections require prescription antifungal treatment and do not resolve without it. In rare cases, persistent yellow nails across multiple digits can be associated with respiratory conditions, lymphedema, or rheumatoid arthritis — known as Yellow Nail Syndrome — which warrants dermatologist evaluation.

Nail Pitting

Small dents or depressions in the nail surface are strongly associated with psoriasis. Pitting occurs when irregular cell growth in the nail matrix creates small defects in the nail plate. It is the most common nail change in people with psoriasis — appearing in up to 50% of psoriasis cases — and can occur in nails even when there are no visible skin plaques. Pitting also occurs in alopecia areata and, less commonly, in eczema and connective tissue conditions. Even mild pitting across multiple nails warrants evaluation by a dermatologist, as it may indicate an underlying inflammatory skin disease that benefits from early treatment.

Nail Lifting (Onycholysis)

Onycholysis — the separation of the nail plate from the nail bed — appears as a white or yellowish area spreading from the free edge inward. Common causes include trauma (the most frequent cause, particularly in toenails), nail psoriasis, fungal infection, contact with harsh chemicals, thyroid disease, and reactions to certain medications including tetracycline antibiotics. Mild separation at the very tip after a nail trauma is common and usually grows out. More significant separation — particularly if discolored, spreading, or accompanied by pain — warrants medical assessment. Applying nail product over significant onycholysis traps debris and moisture, worsening the condition.

For nail technicians — onycholysis is a contraindication:

Do not apply gel, acrylic, or any nail enhancement over a nail with visible onycholysis. Product applied over separated nail plate traps debris and moisture between the product and the nail bed, significantly increasing the risk of bacterial and fungal infection and worsening the separation. Refer the client to their doctor before proceeding with any enhancement service.

Dark Streaks (Melanonychia)

This is the nail change that requires the most prompt attention. A dark brown or black vertical streak running the length of the nail — particularly one that appears on a single nail, is widening over time, or spreads onto the surrounding skin — should be evaluated by a dermatologist promptly. While dark streaks are commonly caused by trauma (bruising under the nail), medication, or benign pigmentation in darker skin tones, they can in rare but serious cases indicate subungual melanoma — a form of skin cancer that develops under the nail.

The distinguishing feature of melanoma-related streaks is that they tend to widen as the nail grows rather than growing out unchanged, and may extend onto the skin fold at the nail base (known as Hutchinson's sign). Trauma-related dark spots should move clearly toward the tip as the nail grows. When in doubt, see a dermatologist. This is not a wait-and-see situation.

Clubbing

Nail clubbing — where the fingertips enlarge and the nails curve steeply downward over the tip — is associated with chronic low blood oxygen. It develops gradually and is associated with lung conditions, heart disease, inflammatory bowel disease, and liver cirrhosis. Sudden-onset clubbing warrants prompt medical evaluation. Clubbing that has been present for decades in an otherwise healthy person may be a benign familial trait. A doctor can determine which applies.

Spoon Nails (Koilonychia)

Nails that curve upward at the edges — creating a concave, spoon-like shape — are associated with iron deficiency anemia. This is the nail change most clearly linked to a specific nutritional deficiency. Iron-deficiency anemia also typically presents with pale nail beds, fatigue, and brittle nails alongside the shape change. A blood test (ferritin and full blood count) confirms the diagnosis. Koilonychia can also occur with hemochromatosis (iron overload) and certain thyroid conditions.

Key nutrients for nail health — role, food sources, and the signs of deficiency in the nails.

What Vitamins and Nutrients Support Nail Health?

Nail health is built from the inside. The nail matrix produces new nail cells continuously — and the quality of those cells depends directly on the nutritional input available to produce them. No topical treatment can strengthen a nail plate that is already formed; the benefit of nutrition and supplements applies to new growth only. Here are the nutrients with the strongest evidence for nail health:

Protein

The most fundamental nutrient for nail health. Nails are approximately 80–90% keratin protein. Inadequate protein intake is a common cause of thin, soft, slow-growing nails. The recommended daily protein intake for most adults is 0.8–1.0g per kilogram of body weight. Food-first is the safest approach: eggs, fish, chicken, legumes, and tofu are all excellent sources. Most people eating a varied diet get adequate protein, but those on very restrictive eating patterns may not.

Biotin (Vitamin B7)

The most commonly discussed nail supplement — with an important caveat about who it actually helps. Biotin supports the enzymes involved in keratin production. Small studies suggest that 2.5mg/day may improve nail thickness and reduce splitting in people with brittle nails — but primarily in those who have a genuine biotin deficiency or true nail fragility syndrome. Most people eating a varied diet already get sufficient biotin. Supplementing does not improve nails that are already healthy or that are brittle for reasons other than biotin deficiency.

Important safety note: high-dose biotin supplementation (2,500mcg and above) can interfere with certain blood tests, including troponin (cardiac) and thyroid function tests, producing falsely abnormal results. Always inform your doctor and stop biotin 2–3 days before any blood work.

Iron and Zinc

Iron deficiency is one of the most common nutritional deficiencies and one of the most reliably reflected in nail health — producing pale nail beds, spoon nails, vertical ridging, and slow growth. Zinc supports nail plate formation and immune function. Both should be tested before supplementing, as both iron and zinc can be harmful in excess. Supplementation is appropriate only when a blood test confirms deficiency.

Vitamin C

Vitamin C is essential for collagen synthesis — the protein that forms the structural support of the nail bed and surrounding tissue. Deficiency causes brittle nails, difficulty healing hangnails, and slow growth. Most people get adequate vitamin C from diet. Smokers have significantly higher vitamin C requirements.

Hydration

Dehydration is one of the most underestimated causes of brittle nails. The nail plate contains water — typically 18% water content — which contributes to flexibility. Repeatedly wetting and drying the hands (frequent handwashing, dishwashing without gloves, swimming) dramatically reduces the water content of the nail plate, making it brittle and prone to cracking. Daily cuticle oil application — which acts as an occlusive to reduce water loss from the nail plate — and drinking adequate water both contribute to nail plate hydration.

Evidence-based daily habits for stronger, healthier nails — organized by time of day.

How Do I Make My Nails Stronger? The Evidence-Based Daily Routine

Nail strength is built gradually — new nail grows at approximately 3mm per month, so it takes 4–6 months to grow out a full nail plate. Changes made to nutrition and habits today will not improve the nails currently on your fingers; they will improve the nails that grow over the next several months. Consistency matters more than intensity.

Apply cuticle oil morning and night: The single highest-impact topical habit. Cuticle oil — jojoba or vitamin E based — penetrates the cuticle and nail plate, reducing water loss and maintaining flexibility. Applied morning and night, it measurably reduces splitting and peeling within weeks

Wear gloves for wet work: Water is the primary environmental cause of brittle nails. Every minute of water exposure temporarily swells the nail plate — and repeated swelling and drying cycles weaken the plate structure over time. Rubber gloves for dishwashing and cleaning are the most impactful single protective measure available

File in one direction only: Back-and-forth sawing creates micro-tears at the nail edge that propagate into larger splits. Always file in one direction, from side to center. Use a fine-grit file (220+ grit) for natural nails

Never peel gel polish: Peeling gel removes nail plate layers — the visible thinness and peeling of nails after gel removal is almost always caused by the client peeling rather than soaking. This point cannot be overstated: always soak with acetone, never peel

Keep nails at a practical length during recovery: Long nails break. During a period of nail recovery — after damage, after gel, after illness — keep nails trimmed to a manageable length to prevent new breakage while the plate recovers

Eat adequate protein daily: The nail matrix needs keratin building blocks consistently. A protein-rich diet (eggs, fish, legumes) is the foundation of strong new growth

When Should I See a Doctor About My Nails?

The answer to this question is simpler than most people expect: see a doctor when a nail change is new, spreading, painful, accompanied by other symptoms, or when you are not sure what is causing it. Nail technicians are not diagnosticians and should not be asked to identify medical conditions from nail appearance — but they can and should flag changes to clients and encourage them to seek medical assessment when appropriate.

The changes that most consistently warrant prompt medical attention are: any dark streak or band on a single nail that was not caused by a known trauma; nail changes accompanied by symptoms elsewhere in the body (fatigue, weight change, hair thinning); significant nail lifting with discoloration; multiple nails developing sudden pitting; and any nail change that is worsening rather than growing out.

For nail technicians — how to raise a nail health concern with a client:

You do not diagnose. You observe and share. A simple, non-alarming approach: 'I noticed something on your nail I want to mention — it's probably nothing to worry about, but it would be worth showing your doctor next time you're in.' This is professional, caring, and leaves the medical assessment where it belongs — with a qualified medical provider.

Nail health from the outside in — start with what goes on the nail.

HEMA-free gel polish is particularly relevant for clients with nail health concerns — HEMA sensitization can cause contact dermatitis and nail fold inflammation that is sometimes mistaken for other conditions. Calyx London gel polish is HEMA-free and TPO-free, reducing one significant external risk factor for clients focused on maintaining healthy nails.

→ Explore the Calyx London HEMA-free collection

Frequently Asked Questions

What do healthy nails look like?

Healthy nails have a smooth surface with faint (if any) vertical ridges, a pink nail bed visible through the nail plate, a white or off-white free edge, and an intact half-moon (lunula) at the base. The cuticle is attached and flexible with no redness or swelling. The nail plate is firm with a slight natural flex and no pitting, horizontal ridges, discoloration, or separation from the nail bed. Growth rate is approximately 3mm per month for fingernails and 1mm per month for toenails.

What do white spots on nails mean?

White spots on nails — medically called leukonychia — are almost always caused by minor trauma to the nail matrix, the area at the base of the nail where new cells are produced. Common causes include bumping the nail, gripping objects, or pressure on the nail base. The spot appears several weeks after the trauma because the affected cells take time to grow to the visible portion of the nail. White spots from trauma grow out with the nail and require no treatment. White discoloration that covers most of the nail surface — particularly with a two-toned pink-and-white pattern — may occasionally indicate liver conditions and is worth showing to a doctor.

What causes ridges on nails?

Vertical ridges (running from base to tip) are extremely common and usually reflect normal aging — the nail matrix becomes slightly less uniform in its cell production over time. They are benign and require no treatment. Horizontal ridges — called Beau's lines — run across the nail and indicate a temporary disruption to nail matrix function at a point in time. Common causes include high fever, severe illness, major surgery, chemotherapy, or significant nutritional deficiency. The ridge grows out with the nail. Multiple simultaneous horizontal ridges across all fingernails suggest a systemic event worth discussing with a doctor.

What nail changes should I see a doctor about?

See a dermatologist or doctor promptly about: any dark brown or black streak on a single nail, particularly if it is new, widening, or extends onto the surrounding skin; nail lifting accompanied by discoloration; significant pitting across multiple nails appearing suddenly; nail clubbing (fingertips enlarging and nails curving sharply downward); spoon-shaped nails; green or black discoloration under the nail; and any nail change accompanied by symptoms elsewhere such as fatigue, hair thinning, or weight change. As a general rule: if a nail change is worsening rather than growing out, it warrants medical assessment.

What vitamins help nail health?

The nutrients with the strongest evidence for nail health are protein (nails are made of keratin protein — adequate daily intake is the foundation), biotin/vitamin B7 (supports keratin production; supplements help primarily those with genuine deficiency — most people eating a varied diet have adequate biotin), iron (deficiency causes spoon nails, pale nail beds, and brittle nails — blood testing should confirm deficiency before supplementing), zinc (supports nail plate formation), and vitamin C (essential for collagen synthesis supporting the nail bed and surrounding tissue). Hydration is also critical — dehydrated nails are brittle nails. Food-first is the safest approach for all of these nutrients.

What is the best thing for brittle nails?

The most impactful interventions for brittle nails are: wearing gloves for all wet work (water exposure is the primary cause of brittleness), applying cuticle oil morning and night (jojoba or vitamin E oil maintains nail plate hydration), eating adequate protein daily, never peeling gel polish (which removes nail plate layers), and filing in one direction only with a fine-grit file. Biotin supplementation (2.5mg/day) may help those with genuine biotin deficiency or brittle nail syndrome, but results take 3–6 months and are not guaranteed. Persistent brittle nails that do not respond to these measures after several months may indicate an underlying condition — thyroid dysfunction, iron deficiency, and psoriasis are among the most common — and warrant a dermatologist visit.

Can nail technicians diagnose nail health conditions?

No. Nail technicians are trained in nail services, not medical diagnosis. A nail technician may observe a change — such as discoloration, lifting, or pitting — and appropriately bring it to a client's attention, but they should not identify it as a specific condition. The appropriate response is a professional, non-alarming observation: 'I noticed something I wanted to mention — it might be worth showing your doctor.' Medical assessment of nail changes belongs with a qualified healthcare provider, dermatologist, or podiatrist. A nail technician who suspects a contraindication — fungal infection, severe onycholysis, active skin condition — should decline the service and recommend medical evaluation before proceeding.

Medical Disclaimer

The information contained in this article is intended for general educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. The nail changes described in this guide are presented to help readers become more familiar with common nail appearances and variations — they are not a diagnostic tool and should never be used to self-diagnose a medical condition. Every individual's nails are different, and the same visual change can have multiple causes, some harmless and some requiring medical attention. If you notice any change in your nails that concerns you, or if a change is new, spreading, painful, or accompanied by other symptoms, please consult a qualified healthcare professional, dermatologist, or podiatrist promptly. Do not delay seeking professional medical advice on the basis of anything you have read in this article. Calyx London US is a professional nail product distributor and is not a medical organization. Nothing in this blog should be interpreted as a substitute for the advice of a licensed medical professional.

Written by the Calyx London US Education Team

Calyx London US is the national distributor of Calyx London professional gel polish in the United States. This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider or dermatologist about any nail or health concerns.