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 such problems as kidney failure, blindness, and heart disease. Insulin helps the body to 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 that are required to keep their blood sugar levels normal. Some patients can overcome the abnormalities with prescription pills. However, sugar levels often remain high despite the pills, and patients need to add insulin injections to their treatment. Different types of prescription insulins vary in how long they are active. Short-acting insulins act quickly and can lower blood sugar levels too much and too quickly in many patients. For this reason, long-acting insulins are often used when insulin is added to diabetes pills. Neutral protamine lispro (NPL), a newer insulin, is one such long-acting insulin, and insulin glargine is another.