Good monitoring is the foundation of good control. Decisions about medication, food and exercise are based on the results of blood glucose monitoring. People with diabetes need to know how to monitor their blood glucose levels, record the results, understand the individual readings and recognize the patterns.
Blood glucose levels vary from hour to hour throughout the day, even when blood sugar is high (above 200) or low (below 50) people may not feel it. Luckily, we have the tools to let us know what blood glucose readings are at any time with a minimum of fuss and mess.
These measurements are important because decisions about diabetes vary from one person to the next. No single formula fits all. A clinician can give you an idea of the duration of action of different insulins, the carbohydrate content of various foods and some of the other variables that affect diabetes. But each unit of insulin and gram of carbohydrate works in a unique way in each individual’s body. Modern technology has provided inexpensive and easy-to-use instruments that make measuring blood glucose a relatively simple job, once you’ve mastered the technique.
How to do it, and how often
The drop or two of blood that you get from a quick pinprick to the tip of your finger is sufficient for the glucose meter to give you an accurate reading. However, don’t use a pin; the recommended tool is a lancet, which fits into a spring-loaded device designed to prick to the necessary depth. Several different lancing devices are on the market, including some with adjustable depth settings.
Wash your hands and make sure they are thoroughly dried, so the blood is not diluted with water. Swabbing with alcohol is not necessary, although some people like to do this. Quickness is a key to avoiding pain. In and out, the spring of the lancet takes only a split second to get the blood you need. Blood will usually come more easily from the sides of the fingertips than the middle.
Drip the drop of blood onto a pad or a strip in the glucose meter. A meter should never be shared, but used only by the person it was bought for to eliminate risk of spreading blood-borne diseases or confusing two peoples’ readings.
The number of daily glucose readings depends on the type of diabetes and the way it is treated. In many people with type 1 diabetes, blood glucose readings are recommended about four times a day — before every meal and at bedtime. In people who have type 2 diabetes and are not taking insulin, two readings a day to two readings per week may be recommended depending on individual blood sugar variability. The results give the information you need at the time you need it. Use the information from glucose monitoring to determine your insulin or oral medication dose and how much the meal should include. Sometimes overnight sticks are necessary to troubleshoot problems of blood glucose ups and downs.
How do blood glucose meters work?
Most of today’s meters use the enzyme glucose oxidase, which reacts with the glucose in the drop of blood on the strip. Usually a color develops, which the meter translates into a numerical reading: the mg/dL blood glucose value. Some meters measure electric current generated by the enzyme in response to the glucose and translate that into the numerical reading.
Different meters provide different information. Meters with a memory keep track of blood glucose levels. If your meter doesn’t have a memory (and sometimes even if it does), you want to keep track yourself by recording each value and perhaps charting them on a simple graph, to observe your patterns. Some meters may also tell you what percent of your readings are in target range, how often they are high and how often they are low.
Most of the newer meters allow the results to be downloaded to a computer. This makes it possible to chart or graph the results and print them out.
What do the numbers mean?
In general, the target range for blood glucose is between 70 and 120 mg/dL, but this is a flexible and moving target for people with diabetes, depending on a number of different factors. An upper level of about 180 is considered reasonable for the period after a meal. For young children who cannot communicate the symptoms of hypoglycemia, parents will want the target range higher; for example, no lower than 100. The goal for nighttime levels may also be higher to avoid overnight lows. The Diabetes Control and Complications Trial (DCCT) showed that complications were minimized if the average blood glucose was 150 mg/dL or less.
Goals must be flexible. If someone is experiencing frequent lows, then higher goals will be appropriate. Again, this is individualized for each person with diabetes.