A diabetic ulcer is not a pressure ulcer. Although they can look similar and even occur in overlapping locations like the heel, these are medically distinct conditions with different causes, different classification systems, and different treatment approaches. Healthcare systems categorize them under entirely separate diagnostic codes, and clinicians use different tools to assess and manage each one.
Why They Get Confused
The confusion is understandable. Both are open wounds that can develop on the feet, both involve tissue breakdown, and both worsen when left untreated. Some clinicians and researchers have historically oversimplified the issue by referring to diabetic foot ulcers as “foot pressure ulcers.” A study in Diabetes Care noted this tendency directly, pointing out that the two have different causes despite several similarities. The distinction matters because treating one like the other can delay healing or miss the underlying problem entirely.
What Causes Each Type
Diabetic Ulcers
Diabetic ulcers develop primarily because of nerve damage and poor blood flow, both complications of prolonged high blood sugar. Nerve damage (neuropathy) affects up to 50% of people with diabetes and is the single biggest driver of diabetic foot ulcers. When the small nerve fibers in your feet are damaged, you lose the ability to feel pain, temperature, and pressure. That means a blister, a pebble in your shoe, or a poorly fitting seam can cause a wound you never notice.
Nerve damage also affects the muscles in your feet. As muscles weaken and atrophy, the foot can change shape, developing deformities like claw toes or hammertoes that create abnormal pressure points when you walk. On top of that, the nerves that control sweating stop working properly, leaving the skin dry and cracked, which opens the door to infection. Meanwhile, diabetes thickens the walls of tiny blood vessels, reduces blood flow, and promotes small clots. The result is tissue that’s starved of oxygen and nutrients, making any wound that does form extremely slow to heal.
Research also points to repetitive shear forces on the sole of the foot as a key factor. Walking creates forces that pull tissue in opposite directions during each step, a process compared to bending a paper clip back and forth until it snaps. This “fatigue failure” builds calluses and raises skin temperature, weakening tissue over time until it breaks down.
Pressure Ulcers
Pressure ulcers (also called pressure injuries or bedsores) form when sustained external pressure compresses soft tissue against a bony prominence. This cuts off blood flow to the area. If the pressure isn’t relieved, the tissue dies. Shear, where skin moves in one direction while deeper tissue stays anchored, compounds the damage. The National Pressure Injury Advisory Panel recognized shear as a core cause back in 2005.
Pressure ulcers develop in people who can’t reposition themselves easily: those who are bedridden, use wheelchairs, or are immobilized after surgery. The cause is external and mechanical, not metabolic. A person without diabetes can develop a pressure ulcer, and a person with diabetes can develop a diabetic ulcer without any sustained external compression.
Where They Appear on the Body
Location is one of the clearest ways to tell them apart. Diabetic ulcers typically form on the foot, especially the forefoot (the ball of the foot, the toes, and the areas beneath the metatarsal heads) in people with neuropathy. These are the spots that absorb the most force during walking. Ischemic diabetic ulcers, where poor blood flow is the main issue, tend to show up on the heel.
Pressure ulcers concentrate over bony prominences where the body’s weight bears down against a surface. About 70% occur at the sacrum (the base of the spine), the ischial tuberosities (the “sit bones”), and the greater trochanter (the outer hip). They also develop on the back of the head, shoulder blades, elbows, heels, and ears. Heels are the one location where the two can genuinely overlap, which is why a heel wound in a diabetic patient requires careful assessment to determine the true cause.
The Heel Overlap Problem
A heel ulcer in someone with diabetes presents a real diagnostic challenge. It could be a pressure injury from lying in bed, an ischemic diabetic ulcer from poor circulation, or both simultaneously. Clinicians distinguish between the two by testing for nerve function and blood flow. A monofilament test, where a thin nylon fiber is pressed against the sole of the foot, checks for sensory nerve loss. Pulse checks, ankle-brachial index measurements, and ultrasound imaging assess whether arteries are blocked or narrowed. If a patient has significant arterial disease and absent pulses, the heel ulcer is more likely ischemic in origin. If the patient has been immobile and the wound sits directly over the heel bone, pressure is the more likely culprit.
In a large cohort study of diabetic foot disease, heel ulcers were far more common in patients whose primary problem was vascular disease rather than neuropathy alone. Neuropathic patients had more forefoot involvement. This pattern helps clinicians sort out what’s driving the wound.
How They’re Classified
Each ulcer type has its own grading system. Diabetic foot ulcers use the Wagner classification, which runs from Grade 0 (a high-risk foot with no open wound) through Grade 5 (gangrene of the entire foot requiring amputation). The middle grades track depth: Grade 1 is a superficial ulcer, Grade 2 reaches tendon or bone, and Grade 3 adds infection. Grades 4 and 5 involve tissue death.
Pressure injuries use the NPIAP staging system, which focuses on how deep the damage extends. Stage 1 is intact but discolored skin. Stage 2 involves partial-thickness skin loss exposing the second layer of skin. Stages 3 and 4 involve progressively deeper damage into fat, muscle, and bone. There’s no equivalent to Wagner’s gangrene stages because pressure ulcers don’t typically cause the kind of widespread tissue death that leads to amputation.
The medical billing system reinforces the distinction. Diabetic foot ulcers are coded under the E10 and E11 categories (Type 1 and Type 2 diabetes with foot or skin ulcer). Pressure ulcers fall under L89 codes, organized by body location and stage. These are completely separate categories in the healthcare system.
Treatment Differences
Because the causes differ, so do the treatments. For diabetic foot ulcers, the priorities are restoring blood flow, controlling blood sugar, and reducing mechanical stress on the wound. If arteries are blocked, a vascular procedure may be needed to re-establish circulation before the ulcer can heal. Off-loading, using special boots, casts, or footwear to take pressure off the wound while you walk, is considered essential for neuropathic ulcers. Blood sugar management matters because high glucose impairs immune function and slows tissue repair at every level.
For pressure ulcers, the cornerstone of treatment is eliminating the pressure that caused the wound. This means repositioning schedules (turning a bedridden patient every two hours), pressure-redistributing mattresses and cushions, and addressing moisture and friction on the skin. Nutrition support plays a major role, since healing requires adequate protein and calories. The wound itself is managed with dressings and debridement, but none of it works if the pressure isn’t relieved.
Both types of wounds benefit from infection control, moist wound healing environments, and adequate nutrition. But the underlying strategy is fundamentally different: fix the blood flow and metabolism for a diabetic ulcer, remove the mechanical force for a pressure ulcer.
Prevention Looks Different Too
Preventing diabetic foot ulcers centers on daily self-care. Inspecting both feet every day for blisters, cuts, and ingrown toenails is the most basic step. Checking the soles with a mirror catches problems you can’t feel due to nerve damage. Properly fitting shoes, with about half an inch of space between the toes and the tip, reduce friction and pressure points. Having your feet measured each time you buy shoes accounts for changes in foot size and shape that happen over time.
Pressure ulcer prevention focuses on the environment and care routine. Specialized mattresses and seat cushions distribute body weight more evenly. Regular repositioning, skin inspections at bony prominences, and keeping skin clean and dry are the main strategies. Risk assessment tools like the Braden Scale help identify patients most likely to develop pressure injuries so that preventive measures can be started early.