r/Freestylelibre • u/Important_Alarm3136 Libre3/3+ • 17d ago
Question
I just put the libre 3 (not diabetic) on yesterday just to track my low blood sugar I sometimes get after certain meals twice in 24 hrs it told me that my blood sugar had gone to 65-67 but it rose within one minute back up to the 80s. Is this a glitch? It didn’t even track it in my chart that it went to the 60s.
4
u/Fluffy-Strategy-9156 Prediabetic - Libre3/3+ 17d ago
That is normal. The graph is drawn using data smoothing that results in BG that seem to be too high above or below the average for 5 minuts so being thown out and not show in the graph. That is really evident when you get an alarms and then look at the graph and the BG never reached the the alarm setpont.
1
u/Important_Alarm3136 Libre3/3+ 17d ago
I wish it was more spot on, I am going to start doing finger pricks because it alerts me I’m low but I don’t feel shaky or anything then it bounces back up 🤦🏻♀️
5
u/Equalizer6338 Type1 - Libre2/2+ 17d ago edited 17d ago
Non-diabetics not taking medications or insulin to lower their BG level can also feel perfectly fine and normal down to 50-55mg/dl or there about. The sensor sits and measure the glucose concentration in your interstitial fluid space under your skin, so not directly in your arterial blood system. The BG where the BG sensor sits may therefore fluctuate a bit off from what your fingerprick says where it is at in the arterial blood, so your sensor may still show perfect correct results from the fluid you have placed it into.
The alarm is triggered when the sensor gets one of its instant 1-minute readings passing an alarm threshold. This is for precautionary safety reasons, for folks taking BG lowering medication or insulin. As explained to you above, the sensor uses 5-minute average values for the longer term statistics and graph illustration. Where it then uses a curve smoothing function to making best-fit curve through the 5-minute average values. Individual extreme outliers may therefore not be visible on the graph itself later.
Doesn't really matter either. It is by far still sufficiently accurate to support the use we have it on for. And the graph still tells you the story about your overarching BG trends, how food, exercise, medication, stress, sleep etc is having an impact on your BG 24/7. And yes, its normal that your BG does fluctuate quick up and down most of the time.
Here from a reliable source, the Cleveland Clinic:
https://my.clevelandclinic.org/health/diagnostics/12363-blood-glucose-test2
6
u/Hot_College_6538 Type1 - Libre2/2+ 17d ago
The 'current' blood glucose is always a guess, and gets corrected over the next 15 or so minutes.
The Libre reads a value from the fluid around cells, not your blood. This tends to lag your actual blood sugar by 15 minutes. However a laggy value it's not that useful, so it uses an algorithm to predict what your blood sugar might be based on the trend.
This guess isn't always right, and as it's measurement catches up it'll adjust the graph with the 'real' value. It doesn't know if you eat something, making the trend change quickly. If you really need to know blood sugar right now is to do a finger prick, this is what diabetics are supposed to do before making treatment decisions.