Diabetes leads to foot ulcers through a chain of three steps, and each one makes the next more likely.
First, the damage. Diabetes can damage the nerves and blood vessels in your feet. This damage can cause numbness and reduced feeling in your feet.
Second, the injury that is not noticed. As a result, your feet are more likely to get injured and may not heal well if they are injured. For example, if you get a blister, you may not notice, and it may get worse. Even small sores or blisters can become big problems if an infection develops, resulting in a diabetic foot ulcer.
Third, the healing that does not happen. Damaged blood vessels mean the supply that repair depends on is reduced. Oxygen is essential for healing, and poor blood flow is one of the reasons wounds do not heal.
There is a fourth factor that sits alongside rather than after. Foot ulcers are partly caused by too much pressure on one part of your foot. A foot that cannot feel pressure cannot shift away from it. You may not feel pressure from shoes that do not fit well, and blisters and sores can develop when your foot presses against your shoe.
None of this is about carelessness, and it is worth saying plainly. This is a loss of the warning system, not a failure to pay attention.
The problem is serious. Foot ulcers are a common reason for hospital stays for people with diabetes, and untreated foot ulcers are the most common reason for toe, foot, and leg amputations in people with diabetes.