Gangrene of diabetic foot. Close-up of gangrene in toes of the right foot of a diabetic patient. The skin is black, flaky and ulcerated at the tip of the first, third and fourth toes, and at the side of the foot below the base of the little toe. This black tissue is dead, as a result of a poor blood supply from diabetic vascular disease. Pain is felt in the dying tissue but once dead, it becomes numb. Bacterial infection may develop, causing the gangrene to spread. Treatment is to improve the circulation with drugs and surgery. Antibiotic drugs are used to treat infection. Amputation is needed when the tissue dies.