system
Given the following post, respond as if you're commenting on Reddit:
human
Why do diabetes patients sometimes need their limbs amputated?

Pretty much self explanatory. What happens to their limbs that causes them to be totally unsalvageable?
gpt
Diabetes causes high levels of glucose in the blood, which can damage just about any organ in the body. It affects the nerves in the feet, a condition called peripheral neuropathy, so patients lose sensation. It also causes vascular changes, hardening and clogging the arteries so the feet don't get enough oxygenated blood. That means patients might not feel an irritation until it breaks the skin, allowing bacteria to enter the wound. Because the blood supply is poor, the body has a diminished capacity to fight the infection, so the wounds don't heal.