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The relatively recent introduction of continuous glucose monitoring or CGM technology has left many people confused about their best options for managing their diabetes. Many people who have diabetes are comfortable using their current blood glucose meters and are reluctant to learn a new system. Others are concerned with the added cost of switching and are unsure of whether their insurance will cover it. I’m going to examine the history and development of this new technology, evaluate its strengths and weakness, and discuss some of the pros and cons of upgrading to the new devices so that diabetics can make more informed choices about their treatment options.

The first CGM system was approved by the FDA in 1999.  The early models did not always produce accurate results, but, since then, there has been a steady improvement in their accuracy. Most models have required calibration with a blood glucose meter that require finger sticks. The latest models do not require a finger stick and can send results directly to a smartphone.  

How Are CGMs Different from Regular Glucose Monitors?

Blood Glucose Monitors give you a very accurate, yet discrete reading of your blood glucose level at the time of the test. Depending on your doctor’s recommendation, you are probably testing your blood 4-10 times a day. When you test your blood, you’re getting a snapshot of your glucose level at that point in time. The problem is that it can sometimes be hard to identify trends in your glucose level because you’re not aware of how it changes between tests. Glucose levels can change significantly based on when and what you eat as well as your activity level. But traditional glucose monitors don’t always give you all the information that you need to see how your behavior affects your glucose levels. 

Continuous Glucose Monitors use a sensor either attached or implanted in your skin. The advantage they have over glucose meters is that they are always on. Because of this, you get a ton more information. Instead of just seeing a few data points each day, you can see trend lines indicating whether your glucose levels are going up or down.  Multiple studies have shown that patients who use CGMs do a better job of maintaining their glucose levels within the desired range, mainly because they are better able to adjust their behavior more quickly than they would if they used the traditional glucose meters.

Some downsides of CMGs

There is some evidence that many people stop using their CGMs after a few months. Although the reasons aren’t entirely clear, researchers believe that people get tired of wearing the device all the time or that they get “information fatigue,” i.e., they find themselves glued to their smartphone or monitor, continually hyper-aware of their glucose levels. Most CGMs have alarms that go off if your glucose levels go above or fall below a predetermined level. That can get annoying and provide too many interruptions to daily life. Working with your doctor to adjust your CGM so that alarms go off less frequently is one solution. Despite these drawbacks, most people who use CGMs like the fact that they are pricking their fingers less often, and they are healthier because they are better able to adjust their behaviors to keep their glucose levels in the proper range.

Insurance Coverage

Many, but not all, private insurers cover CGMs. Check with your own insurer to see which systems they will reimburse you for. Many insurers require that the following conditions be met for you to be covered:

  • A history of hypoglycemia, documented in the physician’s chart/records
  • Presence of hypoglycemia unawareness (lack of symptoms during the early phases of hypoglycemia)
  • Erratic blood glucose levels
  • Suboptimal HbA1c
  • Frequent blood glucose monitoring
  • Having completed diabetes self-management education (Source: Integrateddiabetes.com)

Medicare has also begun to cover CGMs. Here are their requirements to receive coverage:

  • The beneficiary requires a therapeutic CGM. The beneficiary has diabetes mellitus; and,
  • The beneficiary has been using a home blood glucose monitor (BGM) and performing frequent (four or more times a day) BGM testing; and,
  • The beneficiary is insulin-treated with 3 or more daily injections (MDI) of insulin or a continuous subcutaneous insulin infusion (CSII) pump; and,
  • The beneficiary’s insulin treatment regimen requires frequent adjustments by the beneficiary on the basis of therapeutic CGM testing results.
  • Within six (6) months prior to ordering the CGM, the beneficiary had an in-person visit with the treating practitioner to evaluate their diabetes control and determine that the above criteria are met; and,
  • Every six (6) months following the initial prescription of the CGM, the beneficiary has an in-person visit with the treating practitioner to assess adherence to their CGM regimen and diabetes treatment plan. (Source: Dexcom.com)


Many diabetics might see significant health benefits by switching to a CGM.  Some people have been reluctant to switch, partly because they have been worried about costs, and partly because the technology still had some kinks. The latest generation of CMGs, however, are much more accurate and easier to use then the first ones to hit the market in the late 90s.  We’ve also seen a greater willingness to cover the costs of CMGs from both Medicare and private insurers. Because of these recent developments, now might be a good time to ask your doctor if a CGM would be right for you.