Originally published June 4, 2018.
Medtronic’s new 670G system for managing diabetes is exciting, indeed: it combines an insulin pump and CGM (continuous glucose monitor) with an algorithm to keep glucose in range. It’s dubbed a “hybrid closed-loop system” because it has both Auto and Manual Modes, but it is essentially the first iteration of what an Artificial Pancreas will eventually look like.
As a first-generation product, it is tricky to navigate for many new users. We’ve been fortunate to talk with a number of tech savvy PWDs (people with diabetes), including a few who work in the diabetes industry, to gather this rather detailed list of tips. These are not the “official” recommendations you’ll hear from the manufacturer, but rather real-world practical tips that come straight from the mouth of those who’ve used this new Minimed system.
If you’re using or considering the 670G, you may want to print out this guide:
Calibrations: ready, set… make it work!
- Do 3-4 calibrations per day to optimize your sensor readings. That is, go ahead and make all the extra fingerstick BG (blood glucose) checks you do each day anyway, and be sure to enter them as calibrations until you get at least 3-4 in.
- Sometimes the pump nonsensically asks for a confirmatory ‘BG’ to nag you even when you’re pretty sure it’s not needed. Don’t skip this — go ahead and enter a calibration to help improve the sensor readings.
Manual vs. Auto Mode:
When you train on the 670G, there’s an initial 7-day period where you learn to transition from Manual Mode to Auto Mode. You should attempt to optimize your basal rates during this period. Also be aware:
- On the 670G you can use a Temp Basal in Manual Mode but not in Auto Mode, where a Suspend Insulin Delivery on Low (which can’t be timed) is the only option.
- If you revert to Manual Mode after being in Auto Mode for some time, you may need to change your I:C Ratio to a higher, i.e. less aggressive, number to prevent lows (see below).
- Your Insulin-to-Carb (I:C) Ratio will be more aggressive when using the 670. So when you input your setup in Manual Mode the first week, trying decreasing your I:C Ratio by 1-2 points. For example, if your normal I:C Ratio is 10, drop that number to either 8 or 9 in your new pump setup.
Your “Total Daily Basal Dose” goes down in Auto Mode, in part because it is programmed to decrease your Auto Basal to aggressively defend against hypos. The decrease may also be due in part to:
- the more aggressive I:C Ratio
- the fact that many users input “fake carbs” to drive their BG down from the correction target of 150mg/dL to the preset Auto Basal target of 120mg/dL, and
- the more you rely on “fake carb” boluses to redirect corrections down to 120mg/dL, the less need there is for Auto Basal to facilitate these corrections
The normal pump setting for insulin action time is usually 4 hours, but with the 670G, it will probably go down to 3 to 3.5 hours. Be aware of this when inputting your setup. Specifically, the insulin action on prior pumps is typically set at:
- 4 hours for adult PWDs with normal insulin sensitivity
- 5-6 hours for pediatric PWDs or elderly type 1 PWDs who are insulin sensitive
- 3 hours or less for insulin-resistant PWDs
As noted, the 670G will aggressively defend against hypoglycemia while in Auto Mode. If you are using Manual Mode most of the time, a shift to Auto Mode will accommodate mild to moderate upticks in activity without a need to change your target BG from 120 to 150mg/dL.
For strenuous activity, you may need to change the BG target in Auto Mode to 150mg/dL and supplement with carbs.
- Confirmations are requested when your BG exceeds low or high targets, or if you’ve been at your max or minimum Auto Basal Rate for more than 2.5 hours while in Auto Mode.
- Timely pre-meal boluses for meals and snacks will decrease high BGs and minimize the time your Auto Basal is parked at the maximum rate.
- Correcting your BG to ≤120mg/dL with “fake carbs” will put Auto Basal at its minimum and may cause the need for more confirmation BGs. Just so you know!
One of our contributors to this list actually told us: “I’ve concluded that being able to avoid frequent hypos is worth the hassle of managing all the alerts and over-notifications.”
Hope this helps!