For example, a small blister develops from tight shoes. Because the person has reduced sensation, the blister is not noticed immediately. Continued walking damages the skin further, and impaired circulation slows the healing process.
Over time, the injury may become a foot ulcer.
A diabetic foot ulcer is an open sore that can develop when pressure, injury, neuropathy, and other risk factors combine. Some ulcers begin with only a small area of broken skin, making regular inspection particularly important.
Warning signs that should not be ignored
Look for wounds that remain open, repeatedly reopen, or show little improvement.
Other concerning signs include:
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Increasing redness or warmth around the wound.
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Swelling or tenderness.
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Pus, drainage, or an unpleasant odor.
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Darkening skin or tissue that looks black.
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Fever or feeling generally unwell.
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A wound on the sole, heel, or another area exposed to repeated pressure.
If you have diabetes or suspect you may have it, a new open wound on your foot should be assessed promptly rather than left untreated.
Seek urgent medical care for a wound with spreading redness, increasing swelling, pus, blackened tissue, or other signs of infection. Severe symptoms, fever with a rapidly worsening wound, or signs of a serious systemic illness require emergency assessment.
Do not wait for a wound to become painful. Neuropathy can reduce the pain that would ordinarily warn you of a worsening injury.
What should you do if you discover a wound?
Gently clean a minor wound with clean running water, cover it with a clean dressing, and avoid unnecessary pressure on the affected area.
Do not cut away damaged tissue yourself or apply harsh chemicals to the wound.
If you have diabetes, reduced sensation, known poor circulation, or a history of foot ulcers, contact your healthcare team promptly for individualized guidance. Do not rely on home treatment alone when an ulcer or infection may be developing.
The sooner a problematic wound is assessed, the greater the opportunity to prevent complications.
5. Cold Feet, Color Changes, or Unusual Swelling
The fifth group of warning signs involves changes in foot temperature, color, or swelling.
These symptoms are less specific than some of the others. Cold feet, for example, can occur because of room temperature, Raynaud's phenomenon, anemia, thyroid disorders, or ordinary differences in circulation.
Swelling can result from prolonged standing, certain medications, venous problems, or conditions affecting the heart, kidneys, or liver.
However, circulation problems are important to recognize because diabetes can increase the risk of peripheral artery disease, a condition in which narrowed arteries reduce blood flow to the limbs.
How diabetes can affect circulation
High blood glucose can contribute to damage in the blood vessels over time. Diabetes also frequently occurs alongside other cardiovascular risk factors, including high blood pressure, abnormal cholesterol levels, and smoking.
Together, these factors can increase the likelihood of atherosclerosis, in which fatty deposits narrow the arteries.
When blood flow to the feet is reduced, tissues may receive less oxygen and fewer nutrients. Wounds may heal slowly, and the risk of serious complications increases.
Possible signs of peripheral artery disease include:
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Pain or cramping in the calves when walking that improves with rest.
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Feet that feel persistently colder than usual.
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Changes in skin color, including pale, bluish, or unusually dark areas.
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Reduced hair growth on the lower legs or feet.
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Thickened or slowly growing toenails.
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Sores on the toes or feet that do not heal.
Some people with peripheral artery disease experience no obvious symptoms, so the absence of leg pain does not guarantee normal circulation.
Why swelling requires a different kind of attention
Swelling is not a classic stand-alone sign of high blood sugar. It can have many causes, and the pattern matters.
Swelling in both feet may be associated with fluid retention, venous insufficiency, certain medications, or other systemic conditions.
A foot that becomes suddenly swollen, red, warm, or painful may indicate an infection, injury, blood clot, or another problem requiring urgent evaluation.
In people with diabetes and neuropathy, an unusually warm, swollen foot can sometimes signal Charcot neuroarthropathy, a condition in which bones and joints in the foot become damaged despite relatively little pain. Early treatment is important to prevent deformity and further injury.
A suddenly cold, pale, blue, or severely painful foot is a medical emergency, especially if the change develops abruptly or is accompanied by numbness or weakness.
Likewise, sudden one-sided leg swelling, particularly with pain or warmth, needs urgent medical assessment because a blood clot may be responsible. If swelling occurs alongside sudden shortness of breath or chest pain, seek emergency care immediately.
Do not assume that unusual temperature or color changes are simply a consequence of diabetes. They may have other causes, some of which require immediate treatment.
6. Why Diabetes Can Remain Undetected for Years
One reason foot symptoms matter is that type 2 diabetes can develop gradually.
In the early stages, the body may continue producing insulin but become less responsive to it. This is known as insulin resistance. The pancreas initially compensates by producing more insulin, but over time it may no longer be able to keep blood glucose within the normal range.