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A Science Guy's Life on the Medtronic MiniMed 670G Insulin Pump and More.

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Category: Auto Mode

A YEAR LATER – SUCCESS WITH AUTO MODE

Exactly a year ago on this day, I met with my diabetes educator for my Medtronic MiniMed 670G training. Two weeks later I started using Auto Mode.

Along the way, I started documenting my journey on ButDoISay, nearly gave up on Auto Mode and certainly drove my endocrinologist crazy by constantly changing my delivery settings.

Her very words during our last appointment were: “Why change something if it ain’t broken”

Since we have a good rapport my answer was “You know, the scientist in me pushes me to fiddle with the settings. Right?!” And she just laughed.

Finally 100%. I took a year but I think am getting there
Time in Range is 91% in the last 7 days

Fittingly, yesterday for the first time I was 100% in Auto Mode and 100% in Target Range. Woohoo! I just can’t believe how the algorithm has learnt my sugar basal rhythms in the last one year.

But seriously, the last year was also a very stressful year for me. Our youngest daughter was diagnosed with Autism at the start of 2018 and my life was completely changed. All of a sudden I started noticing all the missed milestones and my schedule was now filled with Autism parent training, speech therapy and occupational therapy appointments.

However, the most stressful thing for me was not being ready to accept that my daughter was fine in her world and I am the one who needed to change to make sure I gave her the love and support that she needed to navigate around my world.

One thing though I did not have to worry so much about was: Do I have the correct basals set to deal with the stress and emotional roller coaster that came with our daughter’s diagnosis? This is quite liberating and freeing.

Auto Mode TO THE RESCUE

Through this time, Auto Mode worked like a champ and I can undoubtedly say it has done a better job of adapting to all the stressful events of 2018 than I would have done if it was left to me in Manual Mode.

I no longer have to worry so much about lows when taking my daughters to two separate schools or doing yard work. (I had been diagnosed with uncontrolled severe hypoglycemia in 2013 when I got my first pump. I am also a late onset Type 1)

Despite Auto Mode’s many shortcomings that could keep you awake all night, I am glad that I never gave up.

with auto mode patience is key.

This is my advice: If you are thinking of giving up on Auto Mode because of all those highs that you can’t seem to control, just give it time. For me it has taken close to a year to finally get to where I am comfortable with my numbers.

The Auto Mode algorithm seems to be more adaptive than I even thought. And the more data you feed it, the better it will become.

RECOVERING FROM THE “SENSOR UPDATING” message

You get this dreaded message on your Medtronic MiniMed 670G:

Do not Calibrate. Sensor Updating.”

You know that chances this will mean that you have to replace your all-valuable sensor when it is all said and done. I have not had so much luck with the “updating” part. Almost always the story ends with “replace sensor.”

In most cases the sensor updating message comes on because I have entered consecutive meter BG readings that the sensor does not like.

What i do when i get the “sensor updating” message

To salvage my current sensor this is what I do:

  1. Very carefully remove the tape and completely disconnect the transmitter.
  2. Charge the transmitter once again.
  3. Turn-off the sensor option under Options>Utilities>Sensor Settings.
  4. Remove the transmitter from the charger.
  5. Turn-on the sensor option under Options>Utilities>Sensor Settings.
  6. Reinsert the sensor and start a new connection and go through warmup under
    Options>Utilities>Sensor Settings>Sensor Connection>Start New Sensor.

Shortcomings of the medtronic minimed 670g, automode and guardian sensors

From the onset let me say I think the Medtronic MiniMed 670G and the Auto Mode setting are a big leap forward in glucose control for Type 1 diabetes. Closed loop insulin pump technology is the technology of the future. Personally I foresee the insulin pump becoming an install-and-forget type of medical device in the near-future. While in no way perfect, the first iteration of the MiniMed 670G was a great step forward in this direction.

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morning fasting glucose not exactly where i want them to be

As you can see my morning fasting glucose numbers are running higher than I would like them. I feel well rested in the morning if my numbers are below 120. Above that I wake up feeling tired. I have also noticed that it is in the morning that I get the biggest differences in reading between the Minimed 670G pump Guardian sensor and my BG meter (during other times the readings are within 10 mg/dL of each other but in the morning closer to 20 mg/dL ). Not sure why the sensor consistently under-reports my BG readings, but it is at this time that I would love my sensor to be the most accurate! Most probably it might have to do with the fact that the Auto Mode algorithm is likely most conservative at night.

CHECK BG ESPECIALLY TOWARDS END OF LIFE FOR SENSOR

Double arrows pointing down on your pump is never a good thing especially if the number is 65. But towards the end of life the guardian CGM sensor, it is especially important to counter-check this reading against a BG meter reading. It is quite common for the sensor to yo-yo between lows and highs (displaying double arrows due to false positives and negatives in current readings) especially on the last days of its life. In fact, this instability is normally a signal it is time to change your sensor especially if the numbers do not match BG meter readings.

Decided to counter-check sensor BG before treating low .

A Short Article Review – Optimizing Hybrid Closed-Loop Therapy in Adolescents and Emerging Adults Using the MiniMed 670G System

Link to the Article abstract for this article titled Optimizing Hybrid Closed-Loop Therapy in Adolescents and Emerging Adults Using the MiniMed 670G System by Messer Et al. that was published on Diabetes Care in April 2018. Inbox me to see how we can get you a copy of this paper. Disclaimer.

Bottomline: Your Endo might need to really get aggressive in adjusting your carb-ratios for Auto Mode.


This article is probably the most detailed of any publicly available Medtronic sanctioned studies that actually discusses MiniMed 670G pump and gives guidelines on how to optimize Auto Mode. It delves a little and provides references on how the HCL algorithm used in Auto Mode works and the inputs that can be adjusted when it comes to Auto Mode.

In their trials, the authors worked on optimizing Auto Mode inputs for 31 adolescent and young adult participants (14-26 years old) over a period of 3 months.

The study provides three settings that can be used to tune Auto Mode, namely: carb to insulin ratio, Active Insulin Time (AIT) and Bolus Speed (although this settings is not used or explained for the trial).

The main takeaways from this paper can be summarized as follows:

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Upper Thigh Sensor Insertion Sites ARE more accurate than belly sites

Bottom-line: For accuracy and fewer calibration errors I have found upper thigh sensor insertion sites better than belly sites. These sites take longer to stabilize (about 12-24 hours) but always give me very good accuracy and fewer calibration errors over the life of the sensor. Sensor values seem to match better with meter values for the upper thigh sites over the belly sites.


During my pump training, I was told that Medtronic now officially recognizes the outer side of the upper thigh as an FDA approved insertion site for the Guardian sensor. This was not the case for the Enlite sensor.

To shorten the time it will take the sensor to stabilize and enter Auto Mode, some people suggest inserting a new sensor and leave it in place a couple hours prior to replacing the current sensor. I have had mixed results with this approach with some sensors dying when it comes time to insert the transmitter.

Solution for the Medtronic 670G AutoMode BG Loop

UPDATE 03/13/19 - A new enhanced transmitter to resolve the BG loop issue is being issued to Medtronic MiniMed 670G owners. Please contact your Medtronic Diabetes Educator or call Medtronic directly for one.

This is the email I got from Medtronic after my educator requested for a new transmitter today. However it will take 90-120 days for them to fulfill my order.
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Couple weeks ago, I could not enter Auto Mode on my 670G for three days due to the dreaded “BG Required Loop.” As a solution, I eventually had to change the sensor to be able to re-enter AutoMode.

God knows I have tried to resolve the issue using every advise given online in forums (including trying to “fake” the system by entering a number just above or below your last entry) but these have only worked only a couple times.

What I think Causes the BG Required Loop

At issue I think is the way that the 670G calibrates the Guardian sensor. It seems to be programmed to validate the BG you’ve entered into the system probably based on the ISIG history and its predictive model of where your BG readings are trending towards.

Sounds complicated?

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Kicked Out of Auto Mode….Again!

Guardian Sensor Stability and Auto Mode

I have been trying to get back to Auto Mode for the better part of the day today.

As you can see my readings in manual mode were not so bad and I would say those were stable sensor readings. I am not sure what reading variance the Auto Mode algorithm considers acceptable to enter Auto Mode.

Variance does not look too shabby but Auto Mode did not like it.

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Review – What I Love (and Hate) about the Minimed 670G Auto Mode Feature

The MiniMed 670G in AutoMode. The blue shield means it is all-systems-go and in AutoMode.

The MiniMed 670G in AutoMode. The blue shield means it is all-systems-go and in AutoMode.

There is a lot to like about the Auto Mode feature for the Medtronic MiniMed 670G. This feature is analogous to self-driving technology where a car employing this technology drives along fine until the camera hits a blind spot. The same happens for Auto Mode, it works fine until an unexpected situation arises and the Auto Mode algorithm cannot handle this sudden change.

The closed-loop hybrid system is ground-breaking technology that as a research scientist I really appreciate. Yes it is a work in progress. But its current intricacies and potential to give people with Diabetes better control of their glucose numbers and more freedom to pursue other important things in their lives is really laudable.

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Tunable Settings in Auto Mode for the MiniMed 670G

Tuning Auto Mode for the Medtronic MiniMed 670G is just like tuning an engine. Changing one setting throws off the other settings

Getting Auto Mode settings just right seems to be a balancing act – more fine tuning than just dialing settings up or down

UPDATE 03/13/09 - I have certainly found out that dialing the Carb Ratio and Active Insulin time up and down do not necessarily mean that you will get better control. It is more of a balancing act between these two settings and that is why it is important to work with your endo or educator to tune these settings.

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When it comes to Auto Mode for the MiniMed 670G, tuning the settings to get as close to your sugar targets feels a little more complicated as compared to the manual mode. This is because the closed loop system has a feedback mechanism which will likely throw-off one setting when you change another.

In the course of your day, the system is performing a balancing act between bolus and basal to keep you as close to Auto Mode’s fixed and preset BG target of 120mg/dL by introducing a third input – the micro bolus.

When it is all said and done, the user has control of  two settings only, namely Carb Ratio and Active Insulin time.

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