Ridges on Nails: What Vertical and Horizontal Lines Mean

Take a closer look at your fingernails. You might notice a few faint lines running from the base to the tip, or perhaps a groove stretching across one of them. It's easy to overlook these changes until someone suggests they could mean a vitamin deficiency or an underlying health problem. So, what do ridges on nails actually mean, and should you be concerned?

The answer depends largely on which direction the lines run. Vertical ridges, which extend from the cuticle to the tip, are extremely common and often become more noticeable with age. They're usually harmless. Horizontal ridges are different. They can appear when nail growth temporarily slows or stops, sometimes following an illness, injury or certain medical treatments. Understanding this difference can help you recognise what's normal, what might be affecting your nail growth and when a change is worth discussing with your doctor.

How does a nail grow?

Your nail is made of keratin, the same tough protein found in hair and the outer layer of skin. It is built in a small pocket of living tissue hidden under the cuticle, called the nail matrix. The matrix keeps pushing out new nail plate. The older part slides forward towards the fingertip. This happens slowly. Fingernails grow by about 3 mm a month on average and toenails by about 1 mm. From around the age of 25 that rate drops a little each year. So a fingernail you look at today is a record of the last five or six months of your life, laid down line by line. So nails can carry clues. Anything that disturbs the matrix, even for a few days, can leave a mark that only becomes visible weeks later as the nail grows out.

What causes vertical ridges on nails?

Vertical ridges are thin lines that run from the base of your nail to the tip, almost like the grain of wood. They're very common and usually harmless. According to the American Academy of Dermatology (AAD), lines running along the length of your nails are generally nothing to worry about. There are two common reasons why these ridges may become more noticeable:

1. Natural ageing: Just as your skin changes with age, your nails do too. A review of nail changes in older adults explains that ageing can affect nail thickness, shape and surface texture. This can make vertical ridges more visible over time.

2. Dryness and everyday exposure: Frequent handwashing, washing dishes with detergent and repeated contact with water can leave nails dry and brittle. MedlinePlus notes that prolonged moisture exposure and nail polish can contribute to brittle, peeling nails, making existing ridges more noticeable.

In most cases, vertical ridges are a normal change rather than a sign of vitamin deficiency or illness.

Also read: Brittle Nails Causes: Why Your Nails Split and What Helps

When should you get a vertical nail line checked?

Most vertical ridges don't need treatment. However, a new or changing dark line running along a nail deserves medical attention, particularly if it affects just one nail. Watch for these signs:

• A new or changing dark streak: A brown or black line that appears, widens or changes colour should be examined by a dermatologist.

• Darkening around the cuticle: Pigment spreading from the nail onto the surrounding skin, sometimes called Hutchinson sign, needs prompt assessment.

• Thin, dark lines beneath the nail: These may be splinter haemorrhages, often caused by minor injuries. If they appear without an obvious injury, affect several nails or keep returning, get them checked.

A review of common nail disorders recommends prompt dermatology assessment when nail changes raise concern about cancer. Most nail lines are harmless, and a dark streak doesn't automatically mean cancer. However, a new or changing pigmented streak is worth checking early rather than waiting for it to disappear.

What do horizontal ridges on nails mean?

Unlike vertical ridges, horizontal ridges run across your nails from one side to the other. These grooves are known as Beau's lines. According to the American Academy of Dermatology (AAD), Beau's lines appear when something temporarily slows down or interrupts normal nail growth. Several factors can cause this:

1. Severe illness or high fever: Infections such as dengue, typhoid or other illnesses that put significant stress on your body can temporarily affect nail growth.

2. Major surgery or physical stress: Your body may briefly slow nail growth while recovering from a serious illness or operation.

3. Certain medicines: Chemotherapy and some other medicines can interfere with how nails grow.

4. Underlying health conditions: Some autoimmune diseases and other medical conditions can also contribute to horizontal ridges.

5. Nail injuries: An injury near the base of a nail can interrupt its growth, leaving a groove as it grows out.

These causes are described by MedlinePlus and a dermatology review.

Can you tell when a Beau's line formed?

Interestingly, the position of a horizontal ridge can give you a rough idea of when your nail growth was interrupted. Fingernails grow approximately 3 mm per month, although the rate varies from person to person. Here's a simple way to estimate the timing:

1. Measure the distance between your cuticle and the horizontal ridge in millimetres.

2. Divide that number by three.

3. The result gives you an approximate number of months since the interruption.

For example, a ridge 6 mm from your cuticle may have formed around two months ago. Think back to whether you had a high fever, surgery or another significant illness around that time. The number of affected nails can also offer clues:

• Several nails with similar ridges: This may suggest an illness or event that affected your whole body.

• One nail with a ridge: This is more likely to be related to a local injury or damage near the nail base.

Beau's lines usually grow out naturally once normal nail growth resumes. However, MedlinePlus recommends contacting a healthcare professional if you notice horizontal ridges. The AAD also advises getting checked if you cannot identify what might have caused them.

Why does your thumbnail look like a washboard?

Sometimes, a thumbnail develops several closely spaced horizontal grooves, giving it a washboard-like appearance. This is often caused by repeatedly picking, rubbing or pushing back the cuticle, sometimes without even realising it. The AAD explains that this habit can damage the area where new nail grows, leading to repeated grooves. The good news is that stopping the habit allows healthier nails to grow in gradually. Try leaving your cuticles alone and avoiding repeated pressure around the nail base.

Can a deficiency cause ridges on nails?

People often ask whether ridges mean they are short of a vitamin. The answer depends on the kind of line.

• Thin, spoon-shaped nails that dip in the middle, called koilonychia, are linked with low iron. Our guide to iron deficiency in women explains the symptoms and tests.

• MedlinePlus notes that malnutrition and vitamin deficiency can also affect how nails look.

• Fine vertical ridges on their own are not a reliable sign of any single vitamin shortage.

If you are tired, pale, breathless or losing hair as well, a blood test will tell you far more than your nails can. Our article on vitamin B12 deficiency explains what to test and when. A good everyday diet with dal, eggs, paneer, curd, nuts, seeds, green vegetables and fruit gives growing nails the protein and minerals they are built from.

Other marks that are not ridges

A few nail changes are easily confused with ridges.

• Pitting, many tiny dents like the surface of a thimble, is seen with psoriasis and alopecia areata

• Nails lifting away from the skin underneath can come with thyroid problems, psoriasis or fungal infection

How to care for ridged nails

You cannot iron out age-related ridges, but you can make nails stronger and smoother looking.

1. Rub a little moisturiser or coconut oil into your nails and cuticles after washing your hands and at bedtime.

2. Wear rubber gloves when washing vessels or clothes.

3. Leave your cuticles alone. Do not cut or push them back hard.

4. Keep nails short and file in one direction with a fine file.

5. Buff very lightly, if at all. Heavy buffing thins the nail.

6. Use an acetone-free remover and give your nails breaks from polish.

If you take any medicine or supplement for a health condition, keep taking it as prescribed. Your doctor can tell you if it is linked to nail changes.

When should you see a doctor?

Most vertical nail ridges are harmless and need little more than regular nail care. However, some changes are worth getting checked. According to MedlinePlus, you should see a doctor if you notice:

• Blue or unusually pale nails.

• Clubbed nails, where the fingertips become rounded and enlarged.

• Changes in nail shape or distorted nails.

• Horizontal ridges or white lines.

• White discolouration beneath the nails.

• Small pits or dents on the nail surface.

• Peeling, painful or ingrown nails.

Seek prompt medical attention if you notice thin, dark lines beneath the nails (splinter haemorrhages) or dark pigmentation spreading onto the cuticle (Hutchinson sign). The American Academy of Dermatology (AAD) also recommends seeing a dermatologist for a new or changing dark streak, a nail lifting away from the nail bed, or redness and swelling around the nail, which could indicate an infection.

What your nails are telling you

Most of the time the fine lines on your nails are like the lines on your hands. They come with years, washing and living. They ask only for a little care. A line that runs across the nail is worth a pause and a ruler. It is a small diary entry from a few months ago. Once the reason has passed, it will grow out and be clipped away.

Sources

• 12 nail changes a dermatologist should examine (American Academy of Dermatology)

• Nail abnormalities (MedlinePlus, US National Library of Medicine)

• Common nail changes and disorders in older people: diagnosis and management (Can Fam Physician, 2011)

• Beau lines, onychomadesis and retronychia: a unifying hypothesis (J Am Acad Dermatol, 2015)

• Optimal diagnosis and management of common nail disorders (Ann Med, 2022)

Medical Disclaimer: This article is for general information and is not a substitute for advice from your doctor. Speak to a qualified healthcare professional before starting any supplement, especially if you are pregnant, breastfeeding or taking medication.