LifeAfterDx--Diabetes Uncensored

A internet journal from one of the first T1 Diabetics to use continuous glucose monitoring. Copyright 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014

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Location: New Mexico, United States

Hi! I’m William “Lee” Dubois (called either Wil or Lee, depending what part of the internet you’re on). I’m a diabetes columnist and the author of four books about diabetes that have collectively won 16 national and international book awards. (Hey, if you can’t brag about yourself on your own blog, where can you??) I have the great good fortune to pen the edgy Dear Abby-style advice column every Saturday at Diabetes Mine; write the Diabetes Simplified column for dLife; and am one of the ShareCare diabetes experts. My work also appears in Diabetic Living and Diabetes Self-Management magazines. In addition to writing, I’ve spent the last half-dozen years running the diabetes education program for a rural non-profit clinic in the mountains of New Mexico. Don’t worry, I’ll get some rest after the cure. LifeAfterDx is my personal home base, where I get to say what and how I feel about diabetes and… you know… life, free from the red pens of editors (all of whom I adore, of course!).

Friday, March 23, 2012

The river of life

This is something I’ve been preaching for a number of years, but the message doesn’t seem to be making any headway. Not one to give up on my beliefs easily, here we go again: your blood sugar number doesn’t fucking matter. Period. End of sentence.

I don’t care if you’re at 49 mg/dL or 424 mg/dL. It doesn’t matter.

Not one teensy, tiney little bit.

It’s just a number. And as such, it doesn’t have any value at all.

But the context of that number means everything.

Consider the 49. Is it bad? Of course not. It’s just a number. It can’t be either good or bad. It’s just information, and frankly, not very good information, at that. Now, if I told you more, gave you some context to go along with it, then we would have something to work with.

Exhibit A: You took 12 units of Novolog 1.5 hours ago. Ten minutes ago, your BGL was 79 mg/dL. With that context you can safely say you’re in a world of hurt, and your life just might be snuffed out in the next ten minutes if you don’t take drastic action right now. You have a ton of insulin in your body, and it’s just reaching its peak action. If you do the math, you’ll see that you’re dropping at a rate of 3 mg/dL per minute. With no intervention in ten more minutes you’ll be at 19 mg/dL, pass out, have a seizure, and die.

Exhibit B: You just took first place at Dancing with the Stars. During the grand finale you really worked up a sweat dancing the Lambada. Or was it the Paso Doble? At any rate, as even your mother could have predicted, you waltzed your way right into a hypoglycemia. A pretty bad one, in fact. You bottomed out at 38 mg/dL. But you have a trophy to pick up. Luckily for you, you had the presence of mind to put some glucose tabs into your dancing shoes, which you just took five minutes ago. The glucose. Not the shoes. Well, in this scenario the 49’s not so scary any more. Hell, you’re supposed to wait fifteen minutes after taking the glucose before you test again anyway, not five. Not that I blame you. It would be embarrassing to pass out on national television, after all. Especially in your moment of glory. But in only five minutes, you’re already up by 11 points. Sure, you’re still low, but you’re on the rebound. Mission accomplished. There’s nothing more you can do at this point but wait.

I could just as easily create to “good” vs. “bad” scenarios for the 424 mg/dL but I won’t waste your time.

This is where CGM trace screens rule and rock. A trace screen is a graphic representation of blood sugar over time. It looks like a stock market report. The vertical axis is the level of blood sugar, typically from 40 to 400; and along the horizontal axis is time—it can be three hours, six hours, 12 hours, or 24 hours. Over on the right-hand side is where your blood sugar is now. A connect-the-dots line, called a trace, shows the meandering of your blood sugar over the time period.

Trace screens are your new best friend.

Once you get the hang of reading them, they are the fundamental, indispensable tool for helping you navigate your diabetes. Hell, they’re nothing short of blood sugar GPS.

At a mere glance you can know where you are, and how you got there. Try that with an isolated number on a BG meter! This is why I get so hot under the collar when some people get on a rant about their CGM not 100% syncing up with their meter. Never mind that the meter’s accuracy sucks in the first place, even if meters were 100% accurate, a single number is powerless compared to the flood of informational context you get out of an even moderately accurate CGM.

I think a good comparison is to the instrument panel of an airplane. I used to fly back in the day (the day being pre D-day), and I even have a dusty un-usable commercial pilot’s license to show for it. Now, the instruments in the cockpit were designed to give you some quick information about your aircraft at a glance. You didn’t need to think about what they were telling you. You didn’t have time. You were busy flying the damn plane. Simply sweeping your eyes across the various instruments can quickly tell you some important things like if your plane is up-side-down or right-side-up, if the engines are still running, how close to the ground you are, and how much gas is left in the tanks.

A CGM trace screen tells you the same thing. It’ll show you, at a glance, where your sugar is at, where it was a while ago, and how rapid the change is. That last part is what dictates your response. Rapid changes require quicker and more desperate action than slower changes; and rapid changes—graphically—are shown by steeper lines on the CGM.

Consider these two low blood sugars that mySentry has recorded in the last week:


I’m below target at 80. Now, I really don’t like being below 100. Ever. Being hypo unaware and all. The readout shows a drop from about 200 over the last hour and a half. That’s a drop rate of 1.3 mg/dL/min.


I’m still above target at 101. But note the double-down arrow to the left of the BG readout at the bottom of the screen. Yeppers. I’m still dropping like a fucking stone. The readout shows a drop from about 275 over the last hour. That’s a drop rate of 2.9 mg/dL/min.

Which CGM trace should worry me more? Right! The one with the steeper curve, the sharper, deeper line—showing faster change. You don’t even need to do the math, the sharper the line in the vertical direction, the faster the shit is hitting the fan.

Especially with lows, faster lows… well, technically, faster drops… are more serious, and require more sugar to stop and reverse. Slower lows are less serious, as you have more time to fix them. Generally, but not always, fast drops are associated with waaaaaaay too much insulin while slower drops are associated with only a little too much insulin.

As I’m sure you can imagine, my response to the two lows above was very different. Of course, CGMs also have rate of change alarms, so you can get a head’s up to a steep drop long before it gets low at all.

All the CGMs on the market today have trace screens on the receivers, but they’re limited in size by the size of the device, Med-Ts being a fair bit smaller and lower resolution than Dexcom’s. That said, I always found both of them more than adequate.

Until now, damn it.

It turns out that bigger is better, after all (and I always suspected they were lying to us about that all these years). The much, much, much larger CGM trace screen on the monitor of the Sentry is fucking awesome. At four-and-a-half inches wide and three-and-a-quarter tall, it’s a good 300% larger than the screen on the Revel pump. Oh and it’s resolution is better, too. And it has come color, something I regarded as frivolous at first, but have become quite addicted to. Ummm… That said, however, I think Med-T could have used the color in a smarter way. On the monitor, the glucose targets are thin red lines, the hour line and the trace are both white, on a grey back ground. As I think I mentioned yesterday, the status icons for battery, insulin, telemetry, sensor calibration and sensor age all change from green to yellow to red. I’m good with all that, but I think Med-T missed an opportunity when it came to the alarms. The various “Glucose Alert” screens that pop up when the pump sends an alarm to the Sentry are basically B&W. It would have been cool if falls and rises had been in yellow and low and high alarms flashed red.

Sorry, I got off topic there. But the big screen is awesome, it makes it so easy to take in what’s going on in a glance. And more. The larger screen lets me see finer detail. I’ve used it to judge hypo recovery. Ah…. see that! The trace line is flattening out! The recovery is underway. No need to take more glucose!

I’m using the Sentry to manage my personal diabetes crises in real time.

Next time: A different kind of day at the office.

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