Our Experience with Dex G5

We ~usually~ can get our Dexcom G5 continuous glucose monitor (CGM) to be pretty accurate to the point we use it to make daily decisions. We have had times when it isn't. Here are some of my observations on how we work toward more accuracy and these are only based on our experiences. I wanted to keep notes on what I am learning about Dex as I go along. I'll try to add to and refine this list, so if you have anything to add, please comment below. Note: it is not medical advice, just our experiences and notes.

• Readings are less accurate the first 24 hours. More finger sticks are needed that first 24 hour period. After, it seems to get more and more accurate. 
• Accuracy for us seems to depend on standard deviation. If we are experiencing a lot of highs followed by lows (high SD), it seems less accurate. It also seems to wear out the sensor faster.
• We make sure it's well adhered. We've had times where the filament was half out.
• The transmitter, even a new one, might not be working well, have to call Dexcom to determine this, and has happened to us once (gave error code) but is rare for us.
• If near end of battery life, we have found that sometimes, even though we've not gotten the error code that the transmitter needs to be replaced, it needs to be replaced. The battery might be low enough to not give reliable readings.
• Calibration: we try to calibrate the requested two times a day with finger sticks. We only calibrate when in range even if it is asking for a reading.  We wait until we have a steady arrow in range to calibrate.
• We wash his hands if the meter and Dex are off by more than 25 mg/dL. It may be that the meter is wrong because of dirty hands or contamination. If you have a control solution, check meter calibration periodically or test against the lab value at doctor appointment.
• Placement: We have found that legs are more accurate for him than other places (although he refuses to try the abdomen). We try to find the spot that is most accurate for him.
• Compression lows: if he rolls on the transmitter during sleep, a compression low occurs. We then get a false reading telling us he is low and sometimes, dropping. It takes our Dex a while to recover from this. If it is a great difference between the actual and compression reading, Dex may even go offline with ??? because it knows that something is wrong and will not give a reading until it figures out where he actually is. 
• Certain drugs, like Tylenol or acetaminophen can affect the readings.
• We experience it being less accurate during rapid changes in blood glucose. If he has a rapidly rising or rapidly falling BG, I am less likely to trust it. It takes a while to turn a ship around.
• I always require a finger stick if the Dex reading is very high or very low before treating.
• If I think a sensor isn't working well, I'll pull it. Dexcom will replace any sensor that didn't last or work for 7 days.
• Static electricity can be a problem for us, especially in low humidity winter. He likes to wear nylon basketball shorts which exacerbate the problem. We've tried to fight this by using more fabric softener and cotton shorts. 
• We used to use Opsite Flexfix tape when the adhesive started pulling up. It works okay but can look rather nasty if we use the sensor more than one week. He now prefers Grif Grips. We usually wait until the second week to put the Grif Grip on. 
• We put Skin Tac on first before insertion. This helps keep it on longer.
• Dexcom sensor are only approved for use for one week. I am not telling you to use them more than one week. I will tell you that we often get more than one week from our sensors and in our experience, the second week is often just when the sensor is working very well. (Not always, but sometimes.) To do this, we just restart the sensor when it tells us to insert a new one. Note: I am not recommending this - only telling you we do it.
• In order to get a better A1C, we've set the high alert lower than what we were recommended. Right now, my setting is at 140 mg/dL so that I know he is rising before he is already high.
• The accuracy is affected by dehydration. 
• My son seems to think the latest and greatest iPhones give the best connection to the transmitter. I think any iPhone will do. The data is unclear for this bullet point.

This is NOT meant as medical advice. I am not a medical professional and these are just my notes based on my experiences with my son and for myself. Please consult your own medical team before making medical decisions. If using the Dexcom G5 sensor, please follow the manufacturer's instructions and instruction by your medical professional team.