I was happy last week because my spot-sugar was a "normal" (i.e. non-diabetic) value, about 5½ mmol/l (100 mg/dl). (After the last post, I'm going to try to quote both units.) But I observed at the time that a one-off value is just that, and not particularly important except in the context of all my other values.
Today, my average sugar - all the readings over the last month - dipped below 9 mmol/l (160 mg/dl), for the first time since I started calculating averages. This is not a particularly significant number in diabetes terms, so again this is mainly me playing with numbers rather than anything significant, but nice to see my average getting lower. I note once again that it takes two insulin injections per day to get to this level.
I also measure a statistical property called the standard deviation. It's quite straightforward to calculate, but not trivial. An application like Excel will calculate it for you. It is basically a measure of how much your sugar varies with each measurement. Obviously, if you take one measurement and you're at "really low", and the next measurement at "really high", then you have an average which probably isn't very remarkable, but it'll hide these extreme values.
So possibly of a greater cause for note is that I've got this variance down to about 1.4 mmol/l (25 mg/dl). So my average is 8.9 ± 1.4 mmol/l (160 ± 25 mg/dl). In a healthy person, your pancreas produces sufficient insulin that your body's sugar is pretty constant, so the smaller the it varies, the better. For me, whose pancreas doesn't produce enough insulin, 1.4 represents the smallest variance since I started taking measurements back in 2016. Because I take readings every day, I end up with 30 or so per month, so typically the standard deviation will only change by a tiny fraction per day, so it takes a while to notice much difference in the numbers.