When I was first diagnosed in 2017, the Medtronic 670G closed loop system was the only FDA approved closed loop system. It was the latest and greatest diabetes technology. It was so highly recommended that I of course chose this system over other options. After using it for a few years, I can honestly say there are a lot of things I like about it and there are some drawbacks too.

For some background, this system is made up of the Medtronic 670G Insulin Pump and the Guardian Continuous Glucose Monitor. A closed loop system means the CGM “talks to the pump” and the pump will adjust your basal rate to help keep your blood sugar in range.

The Positives

• I have fewer lows with the closed loop system then I did on MDI or in manual mode on the pump.
• It keeps me pretty stable if I don’t have time to micromanage my BGs
• Having a sensor taught me a lot about how things affect my blood sugar. This level of knowledge has been key to my BG management strategy and great A1c levels

The Negatives

• The algorithm doesn’t manage the dawn phenomenon well. 
  • It is not a predictive technology, it only reacts to what your BGs are doing.
  • Since the sensor reads the interstitial fluid, not actual blood, it runs about 15 minutes or so behind your actual blood readings. This means it is 15 minutes “behind” on all reactions.
• The Guardian sensor isn’t the most accurate on the market (but it isn’t horrible either)
• You can only see your sensor information on the pump itself and you can’t share it with anyone else.
• The algorithm targets a BG reading of 120, which is a bit higher than I like mine and I tend to have more highs when it is in automode than if I manage it myself.
• To reduce basal, you only have the option of setting a temp target to 150 in automode
• In automode, the only way to bolus is to enter the number of carbs you’re eating. It doesn’t factor in fat or protein. As you probably know, 30 g of carbs in rice, hits differently than 30 g of carbs in pizza or 30 g of carbs in a salad with salmon.
• I’m not convinced the pump is very durable. I have had 3 insulin pumps in a two year time frame because each of the first two had critical pump errors and they had to be replaced.
  • This also means the algorithm needed to “learn me” all over again with each replacement. Very frustrating!

Even though there are more negatives than positives on my list, the positives still outweigh the negatives in terms of how much weight they hold.  When automode isn’t effective, I take it out of automode and manage blood sugar myself.  It’s similar to having any other pump/CGM (that isn’t looping). Also, for my friends on MDI, I prefer a pump because I can micro-dose and therefore micro-correct (small inputs=small mistakes). I started on MDI and the two times my pump failed and I had to go back to it while waiting for the new pump to come in. I’ll personally never go back to MDI unless I don’t have another option. MDI works for some though, so I’ll never knock something that works for someone. 

Final verdict: Good enough for now. There is a lot to be said for fewer lows and a somewhat hands off approach. If those are things you value, this could be a decent option. Also be on the lookout for the next version of this system (hopefully this year!). Rumor has it that they fixed a lot of the issues with this one in the new model.

Scott (and Jenny) from the Juicebox Podcast also did a whole episode on this system. Check it out here for even more on this!