My landlady is a diabetic and got cellulitis from a mosquito bite last summer. Her legs were killing her, but she didn't want to go to the doctor and she was on her way to septicemia before she finally decided she needed to go.
Her doctor said if she had waited just another day or two, that she would have been dangerously septic and would probably have been put in the ICU. As it was, she spent time in the hospital, not just for antibiotics, but also to get her sugar under control, along with her blood pressure. She was in pretty bad shape.