Yesterday you watched the arrow tell you direction. Today: the angle of that arrow — how steep it is — tells you something just as important. How fast.
Today's idea
Direction without speed is half the picture. A gentle rise is something you might watch. A fast rise is something to pay closer attention to. A gentle fall often resolves on its own. A fast fall is something else entirely.
Most CGMs use a system roughly like this: one arrow up or down means changing about 1–2 mg/dL (0.06–0.1 mmol/L) per minute. Two arrows in the same direction means 2–3 mg/dL (0.1–0.17 mmol/L) per minute. Three arrows is the rare, urgent case — 3+ mg/dL (0.17+ mmol/L) per minute.
That math turns the arrow into a forecast. A 130 (7.2 mmol/L) with two arrows up is on track to be near 190 (10.6) in 30 minutes if nothing changes. The same 130 with one arrow up will likely be near 160 (8.9). The number you see now and the number you'll see in thirty minutes can be very far apart.
She's going down. But she's going down at a speed I'm comfortable with based on the food that I know is going in.
— Scott Benner, from Pro Tip 1006
The number 75 (4.2 mmol/L) with a flat arrow and the same 75 with a fast-down arrow are not the same situation. Today is the day you stop reading them as if they were.
The speed tells me how much time I have.
Today, when you check your CGM, name the direction first, estimate the speed (gentle? medium? fast?), then read the number. Notice if your sense of urgency shifts when you read those three pieces in that order.
Small Sip #1448 — Stop the Arrows
Did reading direction, then speed, then number change how I felt about any of today's readings?