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

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

I recently set out to compare the two meters out of curiosity. 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.

An “Unscientific” Comparison

The reason I say this is an “unscientific” comparison is because, in a lab setting I would have to measure each reading at least three times (triplicate) for statistical purposes. But in my short study here I am more interested in seeing whether there are any trends that can be observed when it comes to comparing measurements performed using these two meters.

As you can see, the Contour next Link seems to measure consistently higher than the UltraMini over the range of my measurement.


*all measurements in mg/dL

However, no discernible pattern can be seen for the variance meaning it would be hard to adjust one meter’s reading for the other.

One thing I must say is that I have been able to achieve my Hba1c goals while using the both meters so I do think both meters are accurate enough.

Based on my experience and long-term use, I think the Contour next Link is more accurate (closer to the true reading) while the ONETOUCH UltraMini is more precise (more consistent readings).

Surprisingly, in relation to calibrating the Medtronic MiniMed 670G, I have had better luck with the ONETOUCH UltraMini (probably due to its precision) over the Contour next Link supplied by Medtronic.

UPDATE 09/19/2018: I  am having great luck calibrating for Auto Mode using the ONETOUCH UltraMini or the OneTouch Verio over the Contour next Link. At the back of my mind though is the fact that I know that the OneTouch meters are not as accurate as the Contour next Link.

Using the ONETOUCH Verio to calibrate the Medtronic Minimed 670G

The Guardian sensor numbers are awfully close to the OneTouch numbers during calibration which leads me to question whether the Contour next Link despite its accuracy is the best meter to use for calibration. Obviously it would mean a lot of rework if Medtronic was to move away from the Contour next Link since the meter is the standard way of uploading data to Carelink.

Many people have reported online that they think the Guardian sensor under-reports its numbers by close to 20 mg/dL. I think this might be true based on my recent experience. Dilemma is that the 670G seems to conservatively target your glucose numbers to between 120 and 150 mg/dL.

So if it under-reports, it means that it is very likely for your HbA1C to be above 7.0 if your daily average is in the 120-150 mg/dL range.

I am looking forward to seeing my next HbA1C number and will update accordingly.

UPDATE 10/15/2018: HbA1C was 6.8 exactly where my Endocrinologist wanted to see it. Because I am susceptible to severe hypoglycemia, my HbA1C goals were set a little higher.

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.

For sure there is something about the sensor readings that my pump did not like, and after a couple of hours (and in manual mode), the pump requested for a sensor change altogether as you can see below.

Alarm History Medtronic MiniMed 670G

Lots of alarms prior to my the change sensor alarm

Hooray it is now 12:56AM and I just entered Auto Mode. I am….exhausted.

Finally In Auto Mode Again at 1 AM

Getting back into Auto Mode was such a chore that took nearly a whole day.

I am starting to wonder whether Auto Mode is worth all the work.

I have noticed that the Contour Next Link meter, although accurate,  is not as precise. Therefore, it might be contributing to my sensor stability issues by introducing a larger variance.

I will cut back on calibrating the sensor just to when the pump requests for a calibration and see whether that helps.

UPDATE 08/24/2018: I have been using my One UltraMini meter for the last couple days and Auto Mode is working beautifully. Only downside is that I have to enter my values manually and I do not think it is as accurate as my Contour Next Link.

Medtronic Technical Support – Sensor Replacement

I talked to tech support today to see whether two sensors that had failed consecutively could be replaced.

As usual it is quite an ordeal, especially if you are short of time.  The representatives have to follow a script that has been given to them. Many medical companies are so concerned about litigation that they do not allow their customer representatives to freelance.

It is frustrating especially if you are running high or low numbers but having previously worked in a customer-focused position I relate to these guys.

But  long story short, I got the sensors replaced.

TIP: I normally upload my data in CareLink before a technical support call and point the representatives to CareLink as proof that actually my sensor failed and that seems to drive the conversation faster.

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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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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How often Do I Change my Infusion Set?

I have used the MiniMed Quick Set Paradigm infusion set for the last couple years. Medtronic recommends that one changes their infusion set every 48-72 hours.

I am the kind of person who questions why I have to do an oil change every 3000 miles and not 5000 miles but think for the 670G it is important to follow these guidelines.

Any blockage on your infusion set and subsequent high glucose readings will most likely throw Auto Mode and it will take hours before you can go back into Auto Mode. This is such a pain especially in the middle of the night since you will also receive a barrage of notifications to rectify the situation.

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