Have you ever looked closely at your fingernails and noticed strange lines or ridges? While most of us don’t pay much attention to our nails, certain types of lines can actually be clues to what’s going on inside our bodies. From nutrient deficiencies to signs of systemic illness, here’s what science says about the lines on your nails.
1. Vertical Lines (Longitudinal Ridges)
What they look like: Fine, raised lines running from the cuticle to the tip of the nail.
What they may mean:
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Often a normal part of aging. As we get older, our nails may develop more noticeable ridges due to changes in cell turnover in the nail matrix.
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Can also indicate nutritional deficiencies, particularly in iron, magnesium, or vitamin B12.
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Sometimes associated with dry or dehydrated skin, especially in cold climates or with frequent handwashing.
Should you worry? Usually not. If the ridges are mild and develop gradually with age, they are harmless. However, if they are accompanied by brittleness, color changes, or nail thinning, it’s worth checking with a healthcare provider.
2. Horizontal Lines (Beau’s Lines)
What they look like: Deep horizontal grooves or indentations across the nail surface.
What they may mean:
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Often caused by temporary interruption in nail growth, usually due to physical or emotional stress, high fever, or illness.
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Common triggers include COVID-19, pneumonia, chemotherapy, or trauma to the nail.
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May be seen in people with uncontrolled diabetes, zinc deficiency, or circulatory disorders.
Should you worry? Yes, especially if multiple nails are affected. These lines can indicate a past systemic health issue and may help doctors identify when the stress occurred based on the nail’s growth rate (about 3 mm/month).
3. White Horizontal Lines (Muehrcke’s Lines)
What they look like: Paired white lines running horizontally across the nail that do not move as the nail grows.
What they may mean:
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Linked to low albumin levels in the blood, often due to liver disease, kidney disease, or malnutrition.
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Can also appear in individuals undergoing chemotherapy or those with nephrotic syndrome.
Should you worry? Yes. Muehrcke’s lines are a sign of underlying health conditions that affect protein levels in the body. A blood test is recommended if these lines are present.
4. Dark Vertical Lines (Melanonychia)
What they look like: Dark brown or black vertical bands running from the base to the tip of the nail.
What they may mean:
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Often benign, especially in people with darker skin tones, where it’s a normal variation.
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However, if the line is new, darker, wider, or changing shape, it may be a sign of subungual melanoma—a rare but serious form of skin cancer under the nail.
Should you worry? Yes—especially if the line appears on a single nail, spreads to the cuticle (Hutchinson’s sign), or you have no history of trauma. Seek evaluation by a dermatologist as soon as possible.
5. Splinter Hemorrhages
What they look like: Tiny red or brown streaks under the nail, resembling splinters.
What they may mean:
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Commonly caused by minor trauma (e.g., bumping your nail).
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In some cases, associated with infective endocarditis (infection of the heart valves), vasculitis, or autoimmune conditions like lupus.
Should you worry? If you haven’t injured your nail and notice multiple splinter hemorrhages or other systemic symptoms like fever or fatigue, you should consult a doctor.
When to See a Doctor
While not every line on your nails is cause for concern, it’s important to monitor changes over time. You should consult a healthcare provider if:
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You notice sudden or dramatic changes in your nails.
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Lines are accompanied by pain, discoloration, or nail detachment.
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You have other symptoms like fatigue, weight loss, or skin changes.
Bottom Line
Your nails are more than just cosmetic—they’re small windows into your overall health. If you notice unusual lines or textures, don’t ignore them. With proper medical evaluation, you can rule out serious conditions and take steps to support your well-being from the inside out.