A correction here means a bolus with no carbs logged within 30 minutes of it. If corrections keep ending low, or keep ending high, show your doctor. Don't change pump settings off this app.
Every time the Bolus Wizard runs, your Medtronic writes down how much insulin it thinks is still active. That's a free answer key. Here's how this app's math stacks up against it, and how the numbers you punch into the pump stack up against Dexcom.
Same numbers, cleaned up and no swearing. Copy it into a message or the patient portal, or export every entry as a spreadsheet.
Drift is the gap between what your sugar should do and what it actually does. Time is only one cause. These checks dig through your data for the others and rank them, strongest sign first. They point at where to look. They don't diagnose a damn thing, and none of them tell you to change a dose.
Where the line sits between "strong sign", "some sign" and "looks fine" is my call, not a published medical cut-off. Four lean on real numbers: the sensor check calls 20% a strong sign because Dexcom's own user guides put the G6 at 9.8% and the G7 at 8.2% against lab blood, the site-age check's 30 points is about what one published study saw over three extra days on a set, and the correction check measures how far off the pump's own factor the drop landed. The sensor-age check splits your fingersticks by sensor age because both guides show a fresh sensor reading worse (G7: 9.9% in its first two days, 7.2% after). The rest are round numbers picked to be worth a look, nothing more.
Everything after that moment is a guess. Time, food, insulin that's still working and clocks that are set wrong all drag the real number away from the one on the screen. Everything below is a made-up person. None of it's your data.
The meter shows where your blood sugar was the second the blood hit the strip. Then it keeps moving. Sitting still, maybe less than a point a minute. After a meal or a dose, 1 to 2 points a minute is normal, and a big meal can push it past that. Drag the slider and watch the fan open up.
Before you add more, look at your pump's IOB (some pumps call it active insulin). If there's still a pile of it working, that's why the number hasn't moved yet.
Your pump drips a little insulin all day and all night. Those are your basal rates. They cover the sugar your liver dumps out on its own, even when you haven't eaten a thing. Their job is keeping you level between meals.
Most pumps don't count basal in the IOB number. So IOB can say 0 while basal keeps flowing. That's normal, nothing's broken. If your background comes from a daily long-acting shot instead, a late or missed shot fucks up everything after it.
Your pump runs basal off its own clock. If that clock's wrong, every rate change happens at the wrong fucking time, every single day. The meter's clock matters too. Anything you copy out of its memory carries the meter's time, right or wrong.
After a daylight saving change, check the pump and the meter. Many don't change their clocks on their own.
These only turn units and grams into points on the Now page. Copy them off your pump. This app will never tell you how much to take.
Copy your basal schedule off the pump. Each row runs from its start time until the next row kicks in.
This pulls readings straight off Dexcom's Share servers, the same ones the Dexcom Follow app uses. Your phone talks to Dexcom directly. Nothing goes through any other server, and the password never leaves this phone except to Dexcom.
Two catches. Share has to be turned on in the Dexcom app with at least one follower invited, or there's nothing to pull. And this is Dexcom's unofficial back door, not their official API, so they can break it whenever they feel like it.
This pulls up to the last 24 hours from Share. For anything older, log in at clarity.dexcom.com, click the export icon on any report, pick your dates, and bring the .csv file in here. Readings, plus any insulin and carbs logged in the Dexcom app, get merged in without doubling up.
Medtronic doesn't let anything read the pump live without a captcha login, so this is a file. Log in at carelink.minimed.com, find "Data Export (CSV)" on the reports page, pick your dates, download it, and bring it in here.
Your 770G talks to CareLink through the MiniMed Mobile app. The live view syncs every few minutes, but the data that lands in reports and this export goes up about once a day. Open MiniMed Mobile and hit Upload Now right before you export, or the file stops at yesterday. (Older pumps like the 630G and 670G don't upload on their own. They need the CareLink USB stick or the Contour Next Link 2.4 meter plugged into a computer.)
Auto Mode only runs off a Medtronic sensor, so with a Dexcom your 770G is in Manual Mode. Every bolus in the file is one you or the Bolus Wizard put in.
You get every bolus (square and dual-wave too), every carb count and blood sugar punched into the Bolus Wizard, and the pump's own "active insulin" numbers. The Patterns page checks this app's math against those. Straight talk: Medtronic pumps don't work with a Dexcom, so the pump never sees your Dexcom. Whatever you type in is all it knows.
The app can't talk to your pump or meter, so this part's on you. Look at the device, type in the time it shows (AM or PM too), and hit Compare. The app measures it against this phone's clock, which sets itself from the network, and remembers the difference. Do it within a minute of looking or the number's off.
That difference moves your basal schedule on the timeline to when the pump is really running it, and it can fix the time on readings you copy out of the meter's memory. It doesn't change anything on the devices. Fixing the clock on the pump itself is still your job.
Meter accuracy: the ISO 15197 standard lets a home meter be off by up to 15 points below 100 mg/dL and up to 15% at 100 and above, on 95% of readings. So about 1 in 20 can be off by more than that.
Drift speed: Dexcom's own arrow chart calls under 1 point a minute steady, 1 to 2 "slowly rising" or "slowly falling" (the slanted arrow), 2 to 3 a straight arrow, and over 3 a double arrow.
Insulin: the exponential curve from OpenAPS and Loop, the open-source pump software. It peaks at 75 minutes for rapid insulin and 55 for the faster stuff, and ends at the duration you set above.
Food: a basic 3-hour absorption curve. It's there to show the shape. Real meals are all over the place, and fat and protein slow them down.
Time in range and the targets: the 2019 international consensus (Battelino and others, Diabetes Care), which also asks for 14 days of CGM with the sensor on at least 70% of the time. GMI: Bergenstal 2018, Diabetes Care, 3.31 + 0.02392 × your average in mg/dL.
Dexcom accuracy: the G6 user guide reports 9.8% average error against lab blood glucose (325 people, 25,128 pairs), the G7 guide 8.2%. Both guides say blood changes before the fluid under your skin does, which is the lag. Neither puts a number of minutes on it, so this app doesn't either. Both also split accuracy by sensor age: in adults the G7 was off by 9.9% in a sensor's first two days and 7.2% in the middle and at the end, the G6 10.9%, then 9.2% and 9.5%. On day 1 alone, 86.1% of G7 readings landed within 20 points or 20% of lab blood, against 94.6% across the whole wear.
Pump site age: Thethi and others, 2010, Journal of Diabetes and its Complications. 24 pump users, average glucose 123 on day 2 of a set and 164 on day 5. The 4 to 8 AM rise: Porcellati and others, 2013, Diabetes Care.
Active insulin: the MiniMed 770G user guide defines it as bolus insulin you've already received, nothing else. That's why basal never shows up in the pump's number, and why this app leaves Auto Mode micro-doses out when it checks its math against the pump.
All of this is averages. Your body, the pump site, exercise, stress and being sick all shove these numbers around.