Circadian glucose phenomenon

I’ve observed many times that a significant low or high blood sugar event tends to produce a metabolic “echo” 24 hours later. Let’s say that at noon one day you find your blood sugar too high, maybe 250 mg/dL (13.9 mmol/L), and your troubleshooting reveals a bent cannula that impedes steady insulin absorption. You replace the infusion set at a fresh site and your blood sugar then drops into a healthy range.

But then you’re surprised, around noon on the next day, by an elevated BG, perhaps at 180 (10), that cannot be reasonably explained by other factors. Even though the trigger event, in this case a bent cannula, is absent on the following day, the blood sugar still marches upward like some kind of salute to the prior day’s excursion. I’ve experienced this phenomenon many times over many years.

I know that blood glucose levels are the result of a complex interaction of not just glucose and insulin but also of cortisol, adrenaline, thyroid hormones, sex hormones, the immune system, sleep status, and other factors.

This 24 and sometimes 48 and 72-hour circadian echo happens even when the first day’s trigger is removed. I speculate that the body’s powerful circadian rhythm prompts this collection of hormones to anticipate this aberrant glucose excursion repeating and stages what I call a circadian glucose phenomenon.

Here’s a recent example that I experienced. Let me first explain what triggered this hyperglycemia.

My automated insulin dosing system, Loop, contains a protection setting called, suspend threshold. The idea is to set a floor level BG below which the system will suspend all basal insulin deliveries. This safety setting protects you from the inevitable chaos of diabetes.

My Loop program resides on my iPhone and I must have accessed that screen and placed my phone back into my pocket while it was still active. This happened in the late evening, near bed-time. This “pocket-dial” event caused me to set the suspend threshold to a ridiculously high setting. That meant that all my BGs would never exceed my suspend threshold setting and my basal rates were all set to zero.

When I woke up the next morning, here’s the mountain-top CGM trace I saw.

While I made very few changes to diet and exercise, here are the following four overnight traces.

Getting better, but still resonating to the 12/14 trigger.


Pretty good trace but still influenced by the trend started on 12/14.


Finally, four days later and the influence of 12/14 hyperglycemia event is extinguished.

A correlation to this happens when I enjoy a particularly great BG day, I find that the following day tends to follow the previous day’s BG results. This occurs even if I’ve relaxed my eating and exercise standards some on the following day. It’s as if my glucose trends produce an ensuing “stickiness” in the days that follow.