Diabetic foot ulcers are open wounds on the feet that develop in people with diabetes, typically on the sole or bottom of the big toe. They affect between 9 and 26 million people worldwide each year, and someone living with diabetes faces a lifetime risk of 19% to 34% of developing one. These ulcers form because diabetes gradually damages both the nerves and blood vessels in the feet, creating conditions where small injuries go unnoticed and heal poorly.
How Diabetes Causes Foot Ulcers
The process starts with nerve damage. Diabetic peripheral neuropathy is present in about 60% of people with diabetes overall and in 80% of those who develop foot ulcers. When the nerves in your feet stop functioning properly, you lose the ability to feel pain, pressure, and temperature. That means a sharp object, a blister from tight shoes, or a small cut can go completely undetected. Without pain as a warning signal, you keep walking on the injury, making it worse.
Nerve damage also affects the muscles in your feet and legs. When the small muscles lose their coordination, the way your foot absorbs pressure during walking changes. Certain spots, especially the ball of the foot and the base of the toes, end up bearing more weight than they should. Over time, this repeated mechanical stress breaks down the skin.
High blood sugar also stiffens connective tissues throughout the foot. The Achilles tendon becomes less flexible, limiting how far your ankle can bend upward. This forces even more pressure onto the front of the foot with every step. Meanwhile, autonomic nerve damage reduces sweating, leaving the skin dry, cracked, and vulnerable to splitting open.
Blood vessel disease compounds all of this. People with diabetes have higher rates of atherosclerosis, particularly in the arteries below the knee. Persistently high blood sugar damages vessel walls, promotes plaque buildup, and thickens capillary membranes. The result is reduced blood flow to the feet, which means fewer oxygen molecules and immune cells reach the skin. Wounds that would heal in days for a healthy person can linger for weeks or months, and infections take hold more easily.
Warning Signs Before an Ulcer Forms
Foot ulcers rarely appear out of nowhere. The earliest changes are subtle: dry or cracked skin on the soles, thickened calluses in pressure areas, redness that doesn’t fade, or slight swelling around the toes or heel. Because neuropathy dulls sensation, many people first notice a problem when they see drainage or bloodstains on their socks rather than feeling any pain.
Once an ulcer has formed, the signs become more visible. The wound itself appears as a red crater in the skin, sometimes surrounded by a ring of callused tissue. If infection sets in, you may notice increased swelling, warmth, discoloration spreading outward from the wound, and a foul odor. Infected ulcers can deteriorate quickly, especially when blood flow is already compromised. In severe cases, infection can spread to deeper tissues or bone and may lead to gangrene in the affected toes.
Who Is Most at Risk
Peripheral neuropathy is the single biggest risk factor. If you can’t feel a monofilament test (a thin fiber pressed against the sole of your foot during a clinical exam), your risk of ulceration increases dramatically. Beyond neuropathy, several other factors raise the likelihood:
- Poor circulation: Peripheral artery disease reduces the blood supply needed for wound healing and infection control.
- Foot deformities: Bunions, hammertoes, and Charcot foot create abnormal pressure points where skin breaks down faster.
- Previous ulcers or amputations: A history of foot ulcers is one of the strongest predictors of future ones.
- Poorly controlled blood sugar: Chronically elevated glucose accelerates nerve and vessel damage and impairs the immune response.
- Ill-fitting footwear: Shoes that are too tight or too loose create friction and pressure that the person may not feel.
How Foot Ulcers Are Treated
Treatment centers on three priorities: removing dead tissue, protecting the wound from further pressure, and controlling infection if present.
Debridement is usually the first step. A clinician removes dead, damaged, or callused tissue from the wound bed to expose healthy tissue underneath. This creates a cleaner environment for healing and helps topical treatments reach the areas that need them. Debridement is often repeated at regular intervals throughout the healing process.
Off-loading, which means taking pressure off the ulcer, is critical for wounds on the sole of the foot. The gold standard is a total contact cast, a non-removable knee-high cast that redistributes weight across the entire lower leg so the ulcer site bears almost none. A meta-analysis in Frontiers in Endocrinology found that total contact casts produced 22% higher healing rates compared to removable devices. However, they also came with a higher rate of device-related complications such as skin irritation and new pressure sores, particularly compared to therapeutic footwear. Removable walking boots and specially designed shoes are alternatives when casting isn’t practical.
Wound dressings are chosen based on the ulcer’s depth, moisture level, and whether infection is present. The goal is to keep the wound moist enough to support cell growth without creating a breeding ground for bacteria. For infected ulcers, antibiotics are prescribed based on the severity. Mild infections involving only the skin surface are typically treated with oral antibiotics. Moderate or severe infections, especially those involving deeper tissue, exposed bone, or spreading redness, often require hospitalization and sometimes surgical drainage.
How Long Healing Takes
Diabetic foot ulcers heal slowly compared to wounds in people without diabetes. A survival analysis study found the median healing time was 112 days, roughly four months, with standard care. The first signs of a favorable healing trajectory typically appeared around 30 days. If an ulcer hasn’t shown meaningful progress in that first month (shrinking in size, developing healthy pink tissue at the base), the treatment plan usually needs to be reassessed.
Several factors influence healing speed. Shallow ulcers that haven’t reached muscle or bone heal faster than deep ones. Adequate blood flow is essential; ulcers on feet with significant arterial disease may not heal at all without a procedure to restore circulation first. Blood sugar control during the healing period also matters. Persistently high glucose slows the production of new tissue and weakens the immune response at the wound site.
Preventing Ulcers From Developing
Daily foot inspection is the most effective habit you can build. Check the entire surface of both feet, including the soles and between the toes, looking for cuts, blisters, cracks, redness, or any color changes. A small mirror can help you see areas that are hard to reach. Because neuropathy removes your ability to feel problems, your eyes have to do the work your nerves no longer can.
Proper footwear makes a significant difference. Shoes should fit well, with enough room in the toe box and no interior seams that could cause friction. Many people with diabetes benefit from custom-molded shoes or inserts that distribute pressure more evenly. Walking barefoot, even indoors, increases the risk of stepping on something that causes a wound you won’t feel.
Keeping skin moisturized prevents the cracks that serve as entry points for bacteria, but avoid applying lotion between the toes where trapped moisture can cause its own problems. Regular toenail care, ideally by a podiatrist if you have neuropathy, prevents ingrown nails from creating wounds. And maintaining blood sugar as close to target as possible slows the progression of both nerve damage and vascular disease, reducing the conditions that make ulcers likely in the first place.