What Your Nails Can Tell You About Your Health: 8 Signs + Care Tips

Your nails are a particularly interesting case study of this: Nail aesthetics can come with a host of underlying meanings and just general insights on the nails themselves. Here, we break it down with a few remedies and fixes:

Brittle nails tend to be people's most ardent gripe, especially as you age. If you notice this nail issue more and more, it's because nails can weaken with time. "Much like our hair getting thinner with age, our nails become dry and brittle with age as well," says board-certified dermatologist Tanya Kormeili, M.D. However, there are other issues at play with brittleness, especially if age isn't necessarily of concern: It could be a sign of iron-deficiency anemia and even hypothyroidism. 

"When your nails become weaker and thinner, you might experience discoloration with your nails, where they turn slightly yellow," explains Amy Lin, the founder of sundays—a nail care brand focused on wellness. "This is a physical sign that your nails may need a breather from polish." Yellow nails are also often associated with fungal infections, like athlete's foot1, although that's more prevalent on the toes than the fingers.  

Additionally, dietary deficiencies can cause splitting and cracking of the nails, notes Kormelli. 

These are horizontal indented lines that you can likely see—and definitely feel when running over your nails. "Horizontal ridges may develop after a physical stress to the body such as an illness, surgery, medication, or even malnutrition," board-certified dermatologist Joshua Zeichner, M.D., states (a concept also known as Beau's lines, if you've heard the term tossed around). If you do notice some horizontal lines across your nails, it's best to touch base with your derm straight away to make sure there's no systemic condition that might be halting your normal nail growth.

And because beauty always has an internal moment, those ridges (both horizontal and vertical) could also signify nutrition imbalances. If you've recently embarked on a new diet, check in with your nails—those divots could be important signs that the new eating plan might not be working for your body. "Nails are made of mainly hardened proteins," Lin explains (namely, a protein called keratin). "When we're low in protein, calcium, or other vitamins, that can sometimes show up on your fingernails with lines."

White spots have two common culprits. The first is typically pretty minor: You nicked your nail and the white spot is the residue from the trauma. These tiny traumas are actually called punctate leukonychia. And if you notice those dots right after removing polish, it can be a signal for another type of trauma: harsh manis that suffocate your nails: "chances are your nails are dehydrated," says Mary Lennon, president and co-founder of the clean nail care brand côte. However, they sometimes can signal mineral deficiency, most likely a lack of zinc or calcium.

Thickening of your nails is more commonly associated with your toes (although not unheard of for tips too) as it's notably caused by athlete's foot. Fungal overgrowth is actually the cause of tinea pedis, or the fancy name for athlete's foot. It's caused by the overgrowth of fungus like Candida albicans, trichophyton, epidermophyton, and microsporum. In the case of athlete's foot, these fungi thrive in wet, warm conditions—like your feet after being tucked into socks and shoes all day or after a workout. 

This is a serious one—see your doctor right away if you notice any dark or black discoloration on your nails, especially if it feels painful. Melanoma can sometimes cause black lines or stripes to appear on the nail, so pay attention to this clue. "This applies to everyone, of every color and especially if that discoloration extends onto the nail fold as well. That's called Hutchinson sign and associated with melanoma," says board-certified dermatologist Keira Barr, M.D.

Any of the above sound familiar? Here's exactly what to do:

If you feel that your nails are looking off, visit an M.D. to double-check about any of the underlying health conditions noted here (as well as others).

Studies indicate that collagen supplements can support healthy nail growth.* One study found that when patients took collagen daily for 24 weeks, their nail health was better maintained2, including faster growth rates, reduced breakage, and improved appearance.* The same goes for biotin, a form of vitamin B that is often used in hair growth supplements.* Biotin has been shown to support thickness and firmness of nails3.*

Given many of the above nail issues can come down to diet and deficiencies, check and see if there are any you may be dealing with. These tests can be done at your regular checkup. Here are the common ones to look out for:

There's a common myth that your nails need to "breathe"—they don't ("Nails don't actually breathe, as they get their nutrients, oxygen, and blood supply from the bloodstream, not from the air," notes Lennon)—but they do need breaks from polish. This is because polish can be dehydrating for nails, can stain them (hence the yellow above), and may even lead to irritation.  

You can avoid a lot of nail issues—frayed cuticles, snagging, and brittleness—with a little attention. Being diligent about your nail hygiene is a lot like skin care: Sure, your skin is affected by what's going inside, but tending to the outside goes a very long way. Regularly hydrate them with cuticle oils, keep them trimmed and filed (check out our DIY mani guide on best practices), and hydrate the skin around it. "It's important to care for the entire nail area so that your nails stay healthy in general," says Barr. 

Nail issues can be indicators for a whole host of problems. Whatever your nail issue is, be mindful to pay attention to it. Typically it's no cause for alarm—only that you perhaps need better nail hygiene–but if the issues persist, see a specialist.