![]() I generally assume two-thirds of my bolus insulin is gone after two hours, meaning a three-unit bolus at 12 pm has about one unit remaining “on board” at 2 pm. I only add insulin if I don’t have enough on board to get back to my target of 100 mg/dl. Kerri Sparling coined the term “rage bolus,” and it’s very easy to do when you’re on CGM – you notice how slow insulin actually works, particularly after meals. Blogger and diabetes thinker extraordinaire Ms. Always account for “insulin on board” or “active insulin” before taking additional insulin. Never overreact to high alarms with aggressive bolus insulin dosing (“rage bolus”), especially for those on pumps. My alarms are set at 80 mg/dl and 150 mg/dl, allowing me to catch highs and lows very quickly the tradeoff to that tighter range is getting more alarms. For instance, starting with alarms at 70 mg/dl (low) and 250 mg/dl (high) and tightening them over time can help minimize frustration. If CGM alarms become annoying, set them at conservative thresholds or don’t have them on at all. I’ll have a ton more to say on this in my upcoming book. ![]() Changing my relationship to CGM - a partner instead of a nag - makes a huge difference in frustration levels. View CGM values and alarms as a helpful speedometer for diabetes, not a “bad” driving grade. If you’re considering a new CGM, those with lower “MARD” values will typically be more accurate, on average. Obviously insurance and other factors play a role in this decision, so switching on a whim is not always possible. I’ve personally seen great results with the Dexcom G4/G5 and the Ascensia Contour Next meter for calibration. If you do not get good results from one brand or model, switching to another may help - some people see brand-related differences. BG meters and CGMs are not perfectly accurate devices both have inaccuracy and both measure glucose in different areas of the body. If CGM readings do not track well with your BG meter, try switching to a different brand of meter (for calibration) or another CGM brand. Patient innovator Dana Lewis calls this “soaking the sensor,” and it really works. This extends the new sensor’s warm-up and brings much better day one accuracy. When the previous CGM expires, I simply put the transmitter on the new one and then start the official two-hour warm-up. This is best done when the previous sensor session is about to expire (e.g., on day 6.5), meaning I wear two sensors at one time – the current one that is still running and giving me data, and the new one that is inserted into the body but not connected to the transmitter. One trick I use to improve day one accuracy is to insert a sensor, but not “start” the official sensor warm-up for 3-12 hours. Accuracy will eventually decline, though this varies by person and by device – some people wear their CGM sensors for three weeks, while others can’t get more than 7-10 days. ![]() CGMs tend to get more accurate the longer they are worn, so don’t give up if accuracy is frustrating in the first 24 hours. Approach day one with patience and caution – especially for insulin dosing – since this is a limitation of the technology. I find morning and right before bed are great times to calibrate – hands are clean and glucose tends to be stable.ĬGMs have higher inaccuracy on day one, especially in the hours after sensor insertion. Both of those times can drive worse accuracy. Try not to calibrate a CGM when glucose is low or rapidly changing. This strategy has prevented me from taking dangerous insulin overdoses many, many times. Upon a second fingerstick, I often find the CGM is correct and the first meter value was reading falsely high (from not washing my hands!). When the CGM and fingerstick meter values are very different, wash hands and take another fingerstick to confirm the BG meter is actually correct (especially if dosing insulin). These two strategies can help avoid a major source of CGM inaccuracy: dirty hands -> inaccurate BG meter readings -> inaccurate CGM calibration -> worse CGM accuracy. Take CGM calibration extremely seriously: (i) always wash hands before taking a fingerstick OR (ii) when hand washing isn’t possible, wipe the first drop of blood and use the second drop. Separately, I’ve also been very hard at work finishing my upcoming book, Bright Spots & Landmines – stay tuned for updates very soon in diaTribe! Since I often hear frustration that CGMs are not accurate, that alarms are annoying, and adhesive is a pain, I wanted to share some tips and tricks from personal experience and research. I’ve been extremely lucky to use and study CGM since my first summer at diaTribe and Close Concerns seven years ago (over 50,000 hours now!), and I’ve seen this technology’s high points, limitations, and progress. What I’ve learned from 50,000 hours using CGM
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