Ridges in your fingernails are usually harmless, but the direction they run matters. Vertical ridges (running from cuticle to tip) are almost always a normal part of aging. Horizontal ridges (running side to side) are more likely to signal that something disrupted your nail growth, from a severe illness to a nutritional deficiency. Here’s how to tell the difference and when to pay closer attention.
Vertical Ridges Are Usually Normal
Vertical ridges run from the base of your nail to the free edge, like tiny grooves in the nail surface. Most people develop them as they get older, and they become more numerous and prominent over time. This happens because the cells that produce your nail plate slow down and turn over less evenly with age, similar to how skin develops fine lines. These ridges are not dangerous and don’t indicate disease on their own.
That said, vertical ridges can sometimes point to specific conditions:
- Very dry skin or eczema. Chronic dryness around the nail matrix (the tissue under your cuticle where nail grows) can produce more noticeable vertical lines.
- Thyroid problems. An underactive thyroid can cause thick, brittle nails with prominent vertical ridges.
- Iron deficiency. Low iron can cause vertical ridges along with nails that curve inward like a spoon, a condition called koilonychia.
- Low calcium or zinc. Both deficiencies are associated with brittle nails and longitudinal splitting that starts at the free edge and works its way back.
If you’re otherwise healthy and your ridges developed gradually over years, aging is the most likely explanation. If they appeared suddenly, came alongside brittle or splitting nails, or showed up with other symptoms like fatigue or hair loss, a nutritional deficiency or thyroid issue is worth considering.
Horizontal Ridges Signal Disrupted Growth
Horizontal ridges are different. Clinically called Beau’s lines, these are indentations or grooves that run across the nail from side to side. They form when something temporarily stops or slows nail growth at the matrix. Once growth resumes, the dent moves forward as the nail grows out, creating a visible line that travels from cuticle to tip over weeks and months.
Because fingernails grow roughly 3 to 4 millimeters per month, you can actually estimate when the disruption happened by measuring how far the ridge sits from the cuticle. A ridge halfway up a nail that’s about 12 millimeters long suggests the interruption occurred roughly six to eight weeks earlier.
Common causes of Beau’s lines include:
- Severe illness with high fever. COVID-19, pneumonia, measles, mumps, strep infections, and even heart attacks can all trigger them.
- Chemotherapy. Cancer treatment frequently disrupts the rapidly dividing cells in the nail matrix.
- Nail injury. Slamming a finger in a door or dropping something heavy on a toe can cause a single horizontal dent on that nail only.
- Long-term use of acrylic or gel nails. Repeated application and removal damages the nail plate over time.
- Chronic conditions. Diabetes, peripheral artery disease, underactive thyroid, and Raynaud’s phenomenon can cause recurring Beau’s lines because they interfere with blood flow to the nail matrix.
- Nutritional deficiency. Protein deficiency, zinc deficiency, and the general malnutrition associated with chronic alcoholism are all documented triggers.
If you see horizontal ridges on just one nail, the cause is most likely local trauma. If they appear across multiple nails at the same position, that points to a systemic event, something that affected your whole body at a specific point in time.
Ridges vs. Other Nail Changes
Not every nail irregularity is a ridge. Psoriasis, for example, typically causes tiny pits in the nail surface rather than long grooves, along with white spots, a yellowish “oil drop” discoloration, or the nail lifting away from the bed. About half of people with psoriasis develop nail changes at some point, and nail involvement can precede joint symptoms of psoriatic arthritis by years.
Splitting or peeling at the nail tip is also distinct from ridging. Brittle nail syndrome, which involves the nail flaking apart in layers at the free edge, can result from low calcium, zinc deficiency, or chronic dryness, but it looks different from the grooves associated with aging or illness.
What You Can Do About Ridges
For vertical ridges caused by aging, there’s no medical treatment needed, but you can minimize their appearance. Keeping your nails and cuticles moisturized helps. Look for hand creams or cuticle oils that contain ingredients like petroleum jelly, lanolin, or alpha-hydroxy acids, which help lock in moisture. Gentle buffing with a fine-grit buffer can smooth out minor ridges, but avoid doing this more than once every couple of weeks. Over-buffing thins the nail plate and makes it weaker.
For ridges tied to a nutritional deficiency, addressing the deficiency resolves the nail changes over time, though you’ll need to wait for the affected portion to grow out completely. Since a fingernail takes about four to six months to grow from cuticle to tip, it can take that long to see full improvement.
Horizontal ridges from a one-time illness or injury simply grow out on their own. There’s nothing you need to do other than wait. If they keep appearing on multiple nails without an obvious cause like a recent illness, that pattern is worth bringing up with a healthcare provider, especially if you’re also noticing color changes in your nails. The Mayo Clinic specifically flags discoloration combined with horizontal ridges as something that warrants evaluation for an underlying condition.