When we talk about nail care, we’re usually thinking about the latest nail art trends, fresh chrome finishes or scheduling that long-overdue pedicure. But your nails are doing a lot more than just serving looks – they’re actually a direct window into your systemic health.

For the millions of Black folks navigating life with diabetes or prediabetes, changes in your toenails and fingernails (like sudden yellowing, brittleness, thickening or distinct ridges across the nail bed) are often the first subtle warning signs that your blood sugar levels need a little extra love or that your circulation is acting up. Because diabetes can impact nerve sensitivity and blood flow, a minor ingrown nail or a neglected fungal infection can quickly escalate into a serious complication if left unchecked.

What’s happening in your body

“Data from the Department of Health and Human Services’ Office of Minority Health shows that 13.4% of Black men and 12.7% of Black women have been diagnosed with diabetes,” stresses Anne Kamwila, Healthcare Policy Analyst. “To understand how diabetes affects your nails, you have to look at your circulatory and nervous systems. When you have diabetes, your body struggles to regulate the amount of glucose (sugar) in your blood.”

Over time, chronically high blood sugar acts like sandpaper on the inside of your blood vessels, causing severe damage to the tiny capillaries that deliver oxygen and nutrients to your extremities, specifically your toes and fingers, the Society for Vascular Surgery explains. At the same time, this high blood sugar damages your nerves, a condition known as diabetic neuropathy.

Because your toes are the farthest body part from your heart, they are usually the very first place to feel the effects of this poor circulation and nerve damage. Without proper blood flow, your nail beds cannot grow healthy, strong tissue, leaving your nails vulnerable to damage and disease.

Common causes of diabetic nails

When a diabetic patient notices changes in their nails, it is usually a combination of poor circulation, nerve damage and a weakened immune system that creates a perfect storm.

Fungal infections (Onychomycosis): This is the number one cause of nail changes in people with diabetes. Fungi absolutely thrive in warm, dark and sweet environments. Because high blood sugar literally leaves extra glucose in your bodily tissues, it provides an all-you-can-eat buffet for fungal infections. The Mayo Clinic notes that this causes the nails to become thick, brittle, crumbly and turn an unsightly yellow or brownish-black color.

Peripheral arterial disease (PAD): Poor blood circulation means your nail matrix (the root where the nail grows) is starving for oxygen. According to the Cleveland Clinic, this nutrient deficiency causes nails to grow very slowly, become thin and fragile or develop deep horizontal ridges on their surface.

Unnoticed trauma: Because diabetic neuropathy causes numbness in the feet, you might stub your toe, drop something on your foot or wear shoes that are entirely too tight without ever feeling the pain, the Mayo Clinic explains. This repeated, unnoticed trauma causes bleeding under the nail (subungual hematoma), making the nail appear black or purple, and often leads to the nail separating from the nail bed.

Diagnosis and treatment

If you notice significant changes in your nails, you should not just cover them up with a fresh coat of dark polish. It is crucial to seek a professional medical evaluation to prevent minor issues from progressing to severe infections.

For diabetic nail issues, your best line of defense is a podiatrist (a specialized foot doctor). During an exam, the podiatrist will check your foot pulses to evaluate blood flow and use a small filament tool to test for nerve numbness. If they suspect a fungal infection, they may clip a small piece of the nail and send it to a lab for testing.

Treatment for fungal infections usually involves prescription-strength topical lacquers or oral antifungal medications. Because diabetic nails are often too thick and hard to cut safely at home with standard clippers, a podiatrist will use specialized medical tools to trim and thin them, preventing painful ingrown toenails that could lead to open wounds. The most effective long-term treatment is strict management of your daily blood sugar levels to prevent damage in the first place.

If you have diabetes, a standard salon pedicure can actually be dangerous. Minor cuts from harsh cuticle clippers or pumice stones can quickly turn into severe ulcers due to poor healing. To protect yourself, always ask the nail technician to gently push your cuticles back instead of cutting them, request that they skip the cheese-grater foot files and consider bringing your own sanitized nail tools from home to ensure the equipment is completely sterile.

What are the early warning signs of diabetes?

According to the National Institute of Diabetes and Digestive and Kidney Diseases, the classic early warning signs of diabetes include having to urinate frequently (especially waking up multiple times at night), unquenchable thirst, extreme fatigue and blurred vision.

For Black individuals specifically, another major early indicator of insulin resistance is a condition called acanthosis nigricans, which presents as dark, velvety, hyperpigmented patches of skin appearing on the back of the neck, in the armpits or in the groin area.

Why can’t diabetics be barefoot?

People with diabetes are strongly advised against walking barefoot, even inside their own homes, because diabetic neuropathy causes a loss of sensation in the feet. If you step on a rogue piece of glass or a sharp tack, you might not feel the puncture wound; because diabetes also severely slows down the body’s natural healing process, that unnoticed, untreated cut can rapidly develop into a severe, bone-deep ulcer or a staph infection that may require amputation.

“In general, any manicure left in place for an extended period of time is not a good idea because you are not seeing what is going on underneath the nail polish,” assistant professor of dermatology Dr. Chris Adigun of the Ronald O. Perelman Department of Dermatology says.

When to see a doctor

While you should have a routine foot exam with your doctor at least once a year, certain symptoms require immediate medical attention.

You need to schedule an appointment with a podiatrist or primary care physician right away if your nail becomes extremely thick, turns black or green or begins to lift away from the skin. Furthermore, you must seek urgent medical care if you notice any redness, swelling or warm skin surrounding the nail, or if the toe starts leaking pus or has a foul odor, as these are clear signs of an active bacterial infection that requires immediate prescription antibiotics.

Bottom line

Changes in your nails, such as thickening, yellowing or brittleness, are common complications of diabetes caused by a combination of high blood sugar, poor circulation and nerve damage. Because diabetes impairs your body’s ability to heal and fight off fungal or bacterial infections, it is critical to leave nail care to the professionals and avoid covering up the problem with cosmetic fixes. By aggressively managing your blood sugar and seeing a podiatrist for safe trimmings and antifungal treatments, you can protect your feet from severe, long-term complications.

Frequently Asked Questions

Can you tell if you have diabetes by your toenails?

While thick, yellow or brittle toenails caused by chronic fungal infections are a strong indicator of poor circulation and high blood sugar, a doctor must perform an A1C blood test to officially diagnose you with diabetes.

Can you live a long life with Type 2 diabetes?

Absolutely, by proactively managing your blood sugar through a balanced diet, regular exercise and prescribed medications, you can successfully prevent severe complications and live a long, healthy, and active life with Type 2 diabetes.

Citations

Merschel M. The challenge of diabetes in the Black community needs comprehensive solutions. www.heart.org. Published July 13, 2021. https://www.heart.org/en/news/2021/07/13/the-challenge-of-diabetes-in-the-black-community-needs-comprehensive-solutions

Society for Vascular Surgery. Why diabetes can damage your blood vessels, and how to know if you’re at risk | Society for Vascular Surgery. vascular.org. Published November 24, 2019. https://vascular.org/news-advocacy/articles-press-releases/why-diabetes-can-damage-your-blood-vessels-and-how-know-if

Mayo Clinic. Nail fungus – Symptoms and causes. Mayo Clinic. Published 2019. https://www.mayoclinic.org/diseases-conditions/nail-fungus/symptoms-causes/syc-20353294

Cleveland Clinic. Nail Matrix: What It Is, Function, Damage & Conditions. Cleveland Clinic. Published February 14, 2023. https://my.clevelandclinic.org/health/body/24734-nail-matrix

Mayo Clinic. Diabetic neuropathy – Symptoms and causes. Mayo Clinic. Published 2022. https://www.mayoclinic.org/diseases-conditions/diabetic-neuropathy/symptoms-causes/syc-20371580

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & Causes of Diabetes | NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. Published 2020. https://www.niddk.nih.gov/health-information/diabetes/overview/symptoms-causes