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My Life on the Medtronic MiniMed 670G Insulin Pump and More.

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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.


This article is probably the most detailed of any Medtronic funded studies out there that actually discusses pump settings used to optimize the Auto Mode settings. It also 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 looked at how to optimize Auto Mode inputs for 31 adolescent and young adult participants (14-26 years old) over a period of 3 months.

It talks of 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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Solution for the Medtronic 670G AutoMode BG Loop

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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Comparison of the Medtronic Contour next Link 2.4 meter and the ONETOUCH UltraMini

I recently set out to compare the two meters since I like to have a back up meter to the Contour Next meter supplied by Medtronic. It is only until recently that AETNA started to approve the Contour Next glucose test strips through my insurance coverage.

So I have been using the ONETOUCH UltraMini for the last 5 years or so since it was the only meter that was fully covered by my insurance without a co-pay on my part.

The difference in readings was all over the place, but the only discernible pattern was that the Contour next Link 2.4 meter read consistently higher than the ONETOUCH UltraMini.

I personally think that the Contour Next is a more accurate meter (closer to the real blood glucose number) but the ONETOUCH UlraMini is more precise (multiple readings from one site are closer).

And this is important since the ONETOUCH UlraMini and ONETOUCH Verio’s superior precision is  key to reducing Auto Mode and sensor errors and especially eliminating the “BG Required Loop” that occurs in Auto Mode.

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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

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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Upper Thigh Sensor Insertion Sites Seem to Take Longer to Stabilize

I have noticed that when I am using the outer side of my upper thigh as my sensor site, it takes such a long time for the sensor to stabilize and enter Auto-Mode for the Medtronic MiniMed 670G.

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

However after stabilizing, from my experience, this site gives the some of the best and consistent sensor readings.

TIP: To shorten the time it will take the sensor to stabilize and enter Auto Mode, you can insert the new sensor and leave it in place a couple hours prior to replacing the current sensor.

Rechargeable Batteries Work with the MiniMed 670G

Sanyo Enloop Rechargeable AA batteries I use with the MiniMed 670G

Sanyo Eneloop Rechargeable AA batteries I use with the MiniMed 670G

I never had luck using AAA rechargeable batteries with the MiniMed 530G. For some reason, the 530G found the batteries not to have enough charge even after I had recharged them completely. Since I started on the MiniMed 670G, I have been using Sanyo Eneloop AA Rechargeable batteries with no issue. The batteries might not last as long as the non-rechargeable ones but they last long enough before they are fully discharged. 

How Do Guardian/Enlite CGM Sensors Work?

Continuous Glucose Monitor

Continuous Glucose Monitoring (CGM) sensors are finicky, expensive and we all know of how much of a process it is for Medtronic to replace faulty sensors. For me, changing Medtronic CGM sensors is a ritual I do not look forward for many reasons. Getting my sensor inserted and working correctly seems to be a hit-or-miss proposition.

But the delicate nature of sensors is due to the fact they are miniature electrodes that are affected by small changes in the environment around them including small movements or presence of interfering chemical substances.

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For Manual Mode Basal Settings are Everything

Importance of Basal Settings

After nearly giving up on my pump, I found the very popular book by Gary Scheiner, Think Like a Pancreas: A Practical Guide to Managing Diabetes with Insulin. (Amazon) – I think this is a must-have book for people who want tight control of their glucose numbers.

At this point I had uncontrolled, severe hypoglycemia. With a new-born baby, this was not just a drag on my life but it was a bit dangerous. I do not know how many gallons of orange juice I drank to counter lows.

I had also not paid attention on the importance of fine tuning my basals. I was using a single basal which gave me big lows at night and when I was doing practically anything that needed me to expend a little energy.

Since many new pumpers are coming from a combination of short acting and long acting insulin injections, the idea of basals is a little foreign as compared to bolusing.

I think educators need to spend a little more time on talking about how basals are the foundation of successful pump therapy.

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