Brittle nails with ridges usually result from one of three things: normal aging, nutritional deficiencies, or an underlying health condition that disrupted nail growth. Vertical ridges running from cuticle to tip are extremely common and generally harmless, while horizontal ridges signal a specific event that temporarily paused your nail’s growth. Understanding the direction and pattern of your ridges helps narrow down the cause.
Vertical vs. Horizontal Ridges
The distinction between vertical and horizontal ridges matters more than most people realize. Vertical ridges, running lengthwise from the base of the nail to the tip, become increasingly common with age. They’re the nail equivalent of wrinkles: the nail matrix (the tissue under your cuticle that produces the nail plate) gradually becomes less uniform in how it lays down keratin, creating subtle lines. By age 50, most people have some degree of vertical ridging.
Horizontal ridges are different. Called Beau’s lines, these are dents or grooves that run side to side across the nail. They form when something interrupts nail growth entirely for a period of time. Because nails grow slowly (roughly 3 to 4 millimeters per month for fingernails), a horizontal ridge typically appears weeks or months after the triggering event. If you notice a groove halfway up your nail, the disruption likely happened two to three months ago.
Nutritional Deficiencies That Weaken Nails
Iron deficiency is one of the most common nutritional causes of brittle, ridged nails. When your body doesn’t have enough iron to support healthy cell production, the nail plate thins and becomes fragile. In more advanced cases, nails can develop a concave, spoon-shaped appearance. This is worth paying attention to because brittle nails can be an early visible sign of low iron before other symptoms like fatigue become obvious.
Severe zinc deficiency and insufficient protein intake can also produce horizontal ridges and brittleness. Zinc plays a direct role in cell division, and without adequate levels, the rapidly dividing cells in your nail matrix slow down. Protein matters because your nails are made almost entirely of keratin, a structural protein. Restrictive diets, eating disorders, and periods of significant illness that reduce appetite can all create these deficiencies.
Biotin (vitamin B7) has gotten the most attention as a nail supplement. In one small study, 2.5 mg of biotin daily for 6 to 15 months increased nail thickness by 25% in women with brittle nails. A second study found that the same dose taken for an average of 5.5 months led to firmer, harder nails in 91% of participants. These results sound promising, but the studies were small, lacked placebo groups, and didn’t measure participants’ biotin levels before starting. Biotin supplements are unlikely to help if you aren’t actually deficient, and true biotin deficiency is rare in people eating a varied diet.
Thyroid Problems and Nail Changes
Hypothyroidism (an underactive thyroid) is one of the more common medical causes of nails that are both brittle and ridged. Thyroid hormones regulate your body’s metabolic rate, and when levels drop too low, the effects reach your nail bed. Cells in the nail matrix divide more slowly, keratin production decreases, and nutrient delivery to the nail bed is reduced. The result is nails that grow slowly, feel dry and weak, and develop an uneven texture.
These nail changes often accompany other hypothyroid symptoms like fatigue, weight gain, dry skin, and feeling cold. If your nails have become noticeably more brittle alongside any of those signs, a simple blood test can check your thyroid function.
Illnesses and Health Events
A wide range of acute illnesses can leave their mark on your nails in the form of horizontal ridges. High fevers, pneumonia, strep infections, COVID-19, and even heart attacks have all been linked to Beau’s lines. The pattern makes sense: when your body is fighting something serious, it diverts resources away from non-essential functions like nail growth. The nail matrix essentially pauses, and when growth resumes, a visible groove is left behind.
Chronic conditions that interfere with blood flow to the nail matrix produce the same effect over longer periods. Diabetes, peripheral artery disease, and Raynaud’s phenomenon (where small blood vessels in the fingers spasm in response to cold) can all cause recurring ridges and brittleness. The nails aren’t getting consistent blood supply, so growth becomes uneven.
Severe emotional stress can trigger Beau’s lines too. Events like a death in the family, divorce, or job loss, along with ongoing anxiety disorders, can disrupt nail growth in the same way a physical illness does.
Skin Conditions That Affect Nails
Psoriasis and eczema don’t just affect the skin on your hands. When either condition involves the skin around or beneath the nail, the nail plate itself can develop pitting, ridging, and brittleness. Psoriatic nail changes are particularly common, affecting up to half of people with psoriasis at some point.
Lichen planus, an inflammatory condition that can affect the skin, mouth, and nails, causes a distinctive pattern. Affected nails lose their shine, develop grooves and ridges, and progressively thin out. As the condition advances, nails may split or stop growing altogether. Lichen planus can affect just one nail or all twenty, and in some cases the damage is permanent.
Environmental and Lifestyle Factors
Before assuming a medical cause, it’s worth considering what your nails go through on a daily basis. Repeated wet-dry cycles are one of the biggest culprits for brittleness. Washing dishes, frequent handwashing, swimming, or working with cleaning products strips moisture from the nail plate and weakens its layered structure over time. Nails absorb water and swell, then dry out and contract. That repeated expansion and contraction makes them prone to peeling, splitting, and cracking.
Nail polish removers containing acetone are particularly drying. Gel and acrylic manicures, while protecting the nail surface temporarily, can leave nails thinner and more fragile when removed, especially if the removal process involves scraping or peeling. Even frequent use of hand sanitizer, which became routine during the pandemic, can contribute to dryness and brittleness.
What Actually Helps
If an underlying condition is causing your nail changes, treating that condition is the only real fix. Correcting an iron deficiency, managing hypothyroidism, or getting psoriasis under control will allow healthy nail growth to resume, though you’ll need to wait several months for the damaged portion to grow out entirely. Fingernails take about six months to fully replace themselves, and toenails take over a year.
For everyday brittleness without a medical cause, moisture is more important than supplements. Applying a plain moisturizer or cuticle oil to your nails and the surrounding skin after washing your hands makes a measurable difference over time. Wearing gloves when cleaning or washing dishes protects against the wet-dry cycling that weakens nail structure. Keeping nails on the shorter side reduces leverage that leads to breakage.
Ridge-filling base coats are a popular cosmetic option. These products work by depositing a film (typically nitrocellulose and various plasticizers) that fills in surface irregularities and creates a smoother appearance. They contain no ingredients that strengthen or repair the nail itself. They’re purely cosmetic, essentially a thin layer of smoothing polish. That’s fine if the goal is appearance, but they won’t address the underlying cause of ridging.
If your nails have changed noticeably over a short period, if horizontal ridges appear on multiple nails at the same level, or if brittleness is accompanied by other symptoms like fatigue or skin changes, those patterns point toward something worth investigating beyond simple wear and tear.