Yesterday I found that my "fasting" glucose was actually higher than it was the rest of the day, except right after meals. So this morning I woke up at 3 a.m. to try to catch the absolute low point, before my liver started putting out glucose in preparation for my normal waking time.
I got 110 mg/dl, even higher than my previous morning's fasting value!
This experiment has been full of surprises, which is why we measure instead of guessing. Apparently my liver is a really, really early riser. So tonight I'm going to wake up and measure at 1 a.m.
My fasting glucose this morning was 98, not significantly different from the last couple of days. I didn't take any other readings until 5:30, when I got 75. I was definitely feeling loopy so I drank a little orange juice right after. 70 is considered hypoglycemic and is where diabetics are counseled to eat something quick so as not to lose consciousness.
The interesting thing about the later measurement is that I didn't eat lunch until 2:30 because I worked through lunch and left at 2:00 to take my boys go-karting (they're on spring break this week.) So the 5:30 measurement was only 3 hours after a rather substantial (but still low-carb) lunch of three slices of leftover cranberry-apple stuffed pork roast. I even got a little sugar from the stuffing. But I was back down to 75 in three hours. The hormonal regulatory system really wants to maintain the glucose level according to the time of day and fights any dose of carbs from a meal.
So far, here are my conclusions:
1. The morning fasting value is probably the best one for measuring long-term trends in an individual, because it occurs under the most uniform conditions. But I bet it varies a lot from person to person even after identical fasting times. They should probably not publish a normal range for that value because someone could easily have a late-rising liver and get consistently "normal" values, but then it skyrockets after they eat breakfast and the liver finally gets going.
2. Even a drastic change in diet produces slow changes in blood glucose. My fasting value averaged 108 over three days of my normal diet but when my diet dropped from ~100 grams/day of sugar to near zero, it's averaged 97, only a 10% drop.
3. The fasting value should absolutely not be considered a daily minimum. My fasting value of yesterday was 97 but my daily average during waking hours was only 91, and the lowest I measured was only 70!
4. I tend to get tired after lunch and this could be due to low blood sugar. So I need to consider eating a smaller or later breakfast and a bigger lunch in order to smooth things out. I've never been a big breakfast eater and it evidently has to do with not needing food because of the big glucose release I get in the morning.
People who study this for a living probably know all this stuff already, but it's more fun to find it out directly, by measuring. The diet will go on to Day 6...