It is well documented that keeping blood glucose levels as close to normal as possible can reduce the risk of the chronic or long-term complications of diabetes, including eye disease (retinopathy), kidney disease (nephropathy), and nerve damage (neuropathy). Accomplishing this task requires knowing what the recommended blood glucose range is, knowing what your blood glucose levels are, and knowing how to bring your levels into range if they are out of goal range.
To help people with diabetes know what they’re aiming for, both the American Diabetes Association and the American College of Endocrinology have published recommended goals for blood glucose control for healthy, nonpregnant adults (see “Blood Glucose Targets”). There are separate blood glucose goals for pregnant women with diabetes. The goals for healthy adults may need to be modified for certain people, including the elderly.
Blood glucose self-monitoring lets you know what your blood glucose levels are and can often help you and your diabetes team figure how to modify your treatment plan if your levels are out of range. Knowing how to use your meter, therefore, and being able to use it effectively are key to maintaining control of your diabetes.
Blood glucose self-monitoring has both immediate and longer-term applications. In the short term, monitoring can detect high blood glucose (hyperglycemia) and low blood glucose (hypoglycemia), which requires immediate action. (Action is usually recommended when blood glucose is 70 mg/dl or lower.) In the long term, monitoring can reveal patterns in your blood glucose levels that can help you and your diabetes team adjust your treatment plan to improve your blood glucose control.
When to check
The number of times you check your blood glucose level each day may depend on your treatment plan and/or your insurance coverage of the supplies needed to check. The times of day you check should be discussed with your diabetes care team. Common times to perform blood glucose monitoring include before meals, after meals, at bedtime, in the middle of the night, and before driving.
Before meals. Premeal blood glucose checks are probably the most commonly recommended checks. The reading taken before breakfast is often referred to as a fasting blood glucose check because it usually comes after 8–12 hours of no food intake. Fasting blood glucose levels provide information about overnight blood glucose control. Monitoring before lunch and dinner provides information about overall diabetes control.
After meals. Your diabetes care team may recommend monitoring approximately 1–2 hours after the start of meals. This result is probably most useful if you check both before and after a meal so that you can compare the two levels. The after-meal result can help you evaluate the effect of any insulin or oral drugs that you take with the intent of controlling after-meal blood glucose levels. These numbers may also help you assess the effects of the types and amount of carbohydrate you eat. You may be advised to check your blood glucose level after meals if your premeal levels are usually within your target range but your HbA1c test results remain above target.
Bedtime. There are at least two good reasons to check your blood glucose level at bedtime. One is to see if it is at a safe level to help prevent you from going low during the night. A bedtime snack may be recommended to keep your blood glucose levels within a safe range overnight. The other is to see how well your treatment plan is working overnight by comparing your bedtime level to your fasting blood glucose level the next morning. Ideally, your blood glucose levels should remain within a fairly close range from the time you go to bed to the time you wake up the next morning. However, this goal may need to be modified to meet individual safety needs.