I started using Dexcom recently and I love it so far but I have a question about the arrows. If I’m reading 60 diagonal down and I treat the low blood sugar, my next few readings might be something like 62 diagonal down, 69 diagonal down, 74 diagonal up. My question is why does the diagonal arrow continue despite the readings going up? It makes it so I have to remember the previous reading to see if I’m actually coming up from the low or if I might need to eat something else.
When you get that reading, you need to eat a measured dose item based on where you want your number to end up and then leave it alone. If for example I want to go from 60 to 80, then I know I need to eat 2 swedish fish as each swedish fish raises my bg 10 points. It then takes 15 minutes in my system for the swedish fish to even be recognized by my Dexcom CGM so there is no point fretting over interim readings. After 15 minutes, if the arrow goes horizontal, I ate the right amount. If the arrow goes up, chances are I ate too much. If the arrow still shows going down I ate too little. Even with a horizontal arrow, my BG will slowly climb back up to 80 from 60 and the arrow will stay horizontal during that process.
This is of course for a drop due to lack of carb in system, not a compression low caused by lying on and burying the transmitter into your mattress.
I think the arrow is based on trend of last 3-4 readings, not just most recent.
This is certainly what I’ve noticed with my G4.
When I first got the G6, I noticed those irrational arrows, too, and they caused me some consternation. They still happen, but I live with them. I’ve never found an explanation, but they don’t happen that often to me anymore (or at least I don’t notice them) and they don’t last long. I take it as a quirk of the system.
When I’m low, the lag between the CGM and what my blood sugar really is is quite noticeable to me. Basically, I will recover from a low blood sugar before the CGM will show that I’ve recovered. I usually do a fingerstick about 10 minutes after I’ve eaten a fast acting carb to reassure myself that my blood sugar is going up.
One thing I find helpful is that as soon as I’ve seen a low and taken action, I put on a timer for 10 or 15 minutes. I try to wait that long and then do a finger stick. I’m a person who is quite anxious about lows so this can be hard for me. At any rate, for me, if I wait for the CGM to reflect that my blood sugar has recovered, I will tend to over treat the low.
The lag between my blood sugar rising and the CGM reflecting that recovery isn’t very long (15 minutes? Maybe even less) but it’s long enough to cause me to over treat.
If you have android phone, you could install xDrip as replacement/addition to dexcom receiver. Many discussion on xDrip if you do search. XDrip can show point difference for each reading, and predict minutes until low limit will hit based on trend.
The arrows can be really misleading—I rely on visual inspection of the line much more than the arrows, since you can often see a flattening off before the arrows catch it, or that a reading is likely a false blip for example (which can easily cause double arrows that are completely misleading). Also because Dexcom trends are about 15 min lagging, it’s really important not to overreact to them when low, especially if you’ve already treated once. You’re probably fine and the Dex hasn’t had a chance to catch up.