Blood glucose monitoring is an essential part of your treatment plan when you have diabetes. Your blood glucose numbers are important to help make the best decisions for optimal blood glucose targets on a daily basis, as well as over time. Self-management of values outside your target range can provide direction for immediate action. Ongoing blood glucose management can help you prevent or delay long-term complications, such as diabetes-related eye disease, diabetic kidney disease and nerve damage associated with diabetes. Additionally, your diabetes care team relies on timely and accurate glucose values to provide recommendations regarding your treatment plan.
A continuous glucose monitor — typically referred to as a CGM — is a system that measures interstitial glucose levels (glucose in fluid between cells) on a continuous basis throughout the day and night. The CGM system is made up of a sensor, a transmitter and a receiver. A tiny sensor about a half-inch long is inserted just below your skin, usually on your belly or arm. From there, an electrode measures your interstitial glucose levels within the tissue fluid rather than directly from your blood. A transmitter attached to the sensor sends glucose information to a wireless receiver. This receiver displays glucose results on a small screen in up to five-minute intervals. It may be a separate device or incorporated into an insulin pump. Some CGM devices can now be incorporated with insulin pumps to adjust insulin delivery to decrease hypo- and hyper- glycemia as well as to increase time-in-range (the percent of time that your blood glucose levels are in your recommended target range). The unit also allows you to set and manage your sensor settings to personalize them for your lifestyle. Since your CGM device is continuously recording your glucose levels, you can see this information at any time, allowing you to track glucose changes and identify trends. Seeing glucose levels in “real time” can help you make decisions throughout the day about how to balance your food, activity and diabetes medications. Some CGMs send information directly to a smartphone or tablet. You can even share your glucose numbers with your loved ones through your smart device.
Type 1 diabetes is an autoimmune disorder in which the immune system attacks and destroys the insulin-producing beta cells in the pancreas. As a result, the pancreas produces little or no insulin. Type 1 diabetes is also characterized by the presence of certain autoantibodies against insulin or other components of the insulin-producing system such as glutamic acid decarboxylase (GAD), tyrosine phosphatase, and/or islet cells.
When the body does not have enough insulin to use the glucose that is in the bloodstream for fuel, it begins breaking down fat reserves for energy. However, the breakdown of fat creates acidic by-products called ketones, which accumulate in the blood. If enough ketones accumulate in the blood, they can cause a potentially life-threatening chemical imbalance known as ketoacidosis.
Type 1 diabetes often develops in children, although it can occur at any age. Symptoms include unusual thirst, a need to urinate frequently, unexplained weight loss, blurry vision, and a feeling of being tired constantly. Such symptoms tend to be acute.
Diabetes is diagnosed in one of three ways – a fasting plasma glucose test, an oral glucose tolerance test, or a random plasma glucose test – all of which involve drawing blood to measure the amount of glucose in it.
Type 1 diabetes requires insulin treatment for survival. Treatment may also include taking other drugs to prevent kidney damage or to treat diabetes-related conditions such as high blood pressure.
Talk with your diabetes care team to see if you qualify for a CGM. The majority of people who use CGMs have Type 1 diabetes. CGM is usually covered if you have Type 1 or take multiple insulin injections daily, monitor your blood glucose (with a meter) at least four times daily, and have frequent hypoglycemia (low blood glucose) and/or hyperglycemia (high blood glucose). CGM may be indicated if you have hypoglycemia unawareness, which is when you do not feel the symptoms or recognize the signs of hypoglycemia. Hypoglycemia unawareness places you at a higher risk for episodes of severe hypoglycemia. Keep in mind that qualifications may vary between insurance plans.
A prescription from your provider is required for CGM. Your diabetes care team may offer insight regarding your individual insurance coverage based on their experience using CGM in diabetes patient care. Fortunately, due to the improvement in the technology, the reliability of the information and the ease of use, more and more insurers are offering coverage for the various CGM systems (i.e. Medtronic, Abbott, and/or Dexcom). If you are interested in learning more, consult with your commercial insurer about the qualifications and coverage for CGM. If you have Medicare, coverage of CGM system supplies and accessories is available when the beneficiary uses an approved Abbott or Dexcom product with a receiver classified as durable medical equipment. Additionally, you must have Type 1 or Type 2 diabetes, be checking blood glucose at home at least four times daily, be on three or more insulin injections or use an insulin pump, and require frequent adjustments to your diabetes regimen. If you are a Medicare beneficiary, you may want to call 1-800-MEDICARE or visit dexcom.com/medicare-coverage for more information.
In any case, be sure and ask about deductibles and copays and how that applies to CGM coverage as well as ongoing coverage for CGM supplies. Keep in mind that your CGM sensor will need to be replaced every seven to 14 days depending on the model with the exception of the implantable sensor (Senseonics), which should be replaced every 90 days.
Currently, three CGM sensors are approved for treatment decisions, Dexcom (G5 and G6), Abbott FreeStyle Libre, and Senseonics Eversense. What that means is that you can make changes to your diabetes care plan based on CGM results alone. The Dexcom G6 should be calibrated (confirm value with a blood glucose meter) in special circumstances, such as when your symptoms do not match your CGM readings. Other sensors require that a blood glucose check with a meter be done at least twice daily for accuracy as well as for treatment decisions including before you take insulin or treat hypoglycemia. The continuous glucose data that a CGM provides allows you to make more informed therapy decisions than you can with finger stick glucoses alone.
Prior to use of the CGM, ensure the system is approved for use for your age (or your child’s age). CGMs have alarm settings that you can set to sound when your glucose level changes, such as with hypoglycemia or hyperglycemia. You can preset or customize the glucose values to prompt the alarm. Some CGMs can also send information immediately to the smartphone to a designated person, such as a parent, partner or caregiver. For children with diabetes, the parent’s phone can be set to alert them when the child experiences hypoglycemia or hyperglycemia at any time of day or night. Likewise, the system may be helpful when dealing with elderly parents who may need assistance with their personal diabetes care.
By using the alarm feature, you may have less severe hypoglycemia — especially if you have hypoglycemia unawareness. The graphic on the CGM screen displays your glucose as it trends downward or upward, including how quickly the changes are taking place. This display can alert you to make timely changes, if necessary, to help keep your blood glucose in a safe target range.
Your diabetes care provider will want to make sure you are equipped with the following to increase the probability of success. Ideally, you should be adequately trained by a diabetes technology expert to get the most out of your device. Upon starting CGM, your education and training should include the following:
• use of the sensor as well as the transmitter and receiver;
• information on the difference between the information your blood glucose meter provides versus the trends with sensor data;
• use of the sensor data that show your blood glucose changes to assist with adjustment of insulin doses;
• the need (or not) for sensor calibration;
• where to place the sensor on the body;
• routine care of the sensor site;
• benefits of alarms to identify falling and rising blood glucose levels.
When compared with a standard blood glucose meter, using a CGM improves surveillance of your glucose levels by giving you feedback throughout the day while requiring fewer finger sticks. Those who gain the most benefit from a CGM are those who use it daily to evaluate glucose trends and assist in therapy treatment decisions. If CGM is a routine part of your life with diabetes, take advantage of it by developing your skills over time to best use these data to analyze your glucose patterns and trends to support your diabetes care decisions for the better.
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