An important concept in insulin therapy is taking “correction doses” of insulin. This means taking extra rapid-acting insulin before a meal to correct for high blood glucose. A common correction dose is 2 extra units of insulin for a premeal blood glucose level above 150 mg/dl; even more will be needed if the level is above 200. Although there is a large range of appropriate correction doses, a typical scale can be found in “Correction Doses.” Correction doses can significantly impact blood glucose levels. For example, if you generally take 6 units of insulin aspart with lunch but your blood glucose level before lunch is 250 mg/dl, your usual 6 units will not adequately lower both the current high blood glucose and the anticipated rise from lunch. If you take 4 additional units of insulin, the correction dose will cover your premeal high glucose and the 6 units will cover your meal. Although this system can take a few weeks to adjust to, most people find it rewarding because they can take action to lower their high blood glucose as soon as they know about it, rather than letting it remain high throughout the day.
Insulin and weight gain
When first starting insulin therapy, many people complain that they are eating and exercising the same amount as before but gaining weight. This occurs because with insulin, the body is able to use glucose that was previously wasted in the urine. Glucose that is not needed right away for energy is stored as fat. Studies have shown that weight gain may lead people, particularly women, to not follow their prescribed insulin regimen. This is a dangerous practice that can lead to sustained high blood glucose and a higher risk of long-term complications. Weight gain with insulin therapy is not inevitable, but avoiding it or reversing it generally requires eating fewer calories and/or exercising more.
Continuing oral medicines
Many people ask whether it is worthwhile to continue their oral medicines once they have started insulin. Many studies have shown that people who use both an oral drug and insulin have better blood glucose control than those taking long-acting insulin alone. Continuing metformin when beginning insulin, for example, can reduce the weight gain that often occurs in the first year of insulin therapy. Sulfonylurea drugs such as glyburide and glipizide can help reduce high blood glucose after meals and are effective when combined with a single injection of long-acting insulin.
Metformin can be continued even when short-acting insulin with meals is introduced. Glyburide and glipizide are generally discontinued when short-acting insulin is begun.
Thiazolidinedione drugs such as rosiglitazone (Avandia) and pioglitazone (Actos) are associated with weight gain and fluid retention when combined with insulin, so they are usually discontinued when insulin therapy is initiated.
Another medicine that is commonly used prior to starting insulin is exenatide (Byetta). This injectable drug is associated with significant weight loss, and many doctors opt to continue exenatide when starting basal insulin. However, it must be emphasized that at this time, the U.S. Food and Drug Administration does not sanction using exenatide and insulin together.
Back to basics
The overall goal in treating diabetes is to maintain optimal blood glucose levels to reduce the risk of diabetic complications. For many people, insulin is the best way to achieve this goal. There is no single right way to begin insulin; a regimen should take individual needs and circumstances into account. Insulin doses and regimens are also likely to change over time as people’s lives—and bodies—change. With just a little bit of knowledge, however, you can begin insulin therapy undaunted and ready to take the next step in controlling your diabetes.
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