Type 2 diabetes mellitus interferes with the body's ability to store energy from food, resulting in high blood sugar levels that can lead to kidney failure, blindness, and heart disease. Insulin helps the body convert food to stored energy and keeps blood sugar levels within the normal range. In type 2 diabetes, body tissues are resistant to the effects of insulin and patients lack effective insulin levels required to keep their blood sugar levels normal. Prescription pills and, if needed, insulin injections can help some patients. However, sugar levels may remain high despite these treatments.