Auto Mode

Final Post – 2 Years Later on Medtronic MiniMed 670G and AutoMode

Considering that Medtronic plans to release the MiniMed 780G this year, I have decided I might as well wind up my blog on my experience with the MiniMed 670G and Auto Mode.

I have compiled a set of final tips/observation for those planning to get the 670G and use Auto Mode based on my 2 year experience with the pump and Auto Mode.

Auto Mode does not adjust for diurnal trends such as dawn phenomenon.

Despite being adaptive, Auto Mode will not adjust for diurnal trends. Medtronic explicitly recommends manual correction for fasting BG numbers related to dawn phenomenon or somogyi effects.

Auto Mode does not work as well for foods high carb or high-fat foods.

Because of the conservative nature of Auto Mode, expect a spike in BG when you eat high glycemic index (GI) foods. Timing is a little tricky with this pump since there is a period of no basal insulin delivery right after bolusing.

Unless my BGs are low or dropping, I typically wait for 30 minutes after bolusing to eat high GI foods.

For high-fat foods like Pizza, you might need an additional bolus after 1 or 2 hours.

Balance between Bolus and Basal is important

Auto Mode works on input from your historical daily total daily dose (TDD). So the dispensing of bolus and basal will be a balancing act, but in relation to the TDD. So if you set your carb ratio to be so aggressive, expect the Auto Mode to cut back on the basal delivered and vice versa.

I think the jury is still out on whether the 50:50 basal bolus ratio is s needed for Auto Mode. According to my Medtronic Educator, a 55:45 bolus-to-basal ratio is the recommended starting point.

Consistency is Key.

Since Auto Mode depends on TDD history, I have found that it is important to keep my daily carb intake consistent. If you miss a meal or two the previous couple days, Auto Mode will scale down the basal to reflect the changes in your TDD.

Too much snacking will get you into trouble.

Although Auto Mode can handle small BG changes, too much snacking will get you in trouble since the system is very conservative in nature. Too much snacking also might require too much bolusing, which will force the pump to scale back on basal to meet the daily TDD limits.

Bolusing for Ghost Carbs will come back to haunt you.

Although it might seem a good idea to inject for “ghost carbs” or fake carbs to adjust for high BG, it is not. Auto Mode assumes that a meal accompanied the ghost carbs. So expect a precipitous drop in BG a couple hours later since Auto Mode does not account for ghost carbs as part of its BG correction process.

Auto Mode is only as good as the accuracy of your sensor.

Make sure that your sensor is as accurate as possible by identifying which sites give you the most accurate readings. Upper Thigh sites work best for me as compared to belly sites.

Change your infusion sites often.

Just as sensor sites, make sure that the site you are using for your infusion sites deliver insulin consistently. Rotate your sites as recommended. If your BG rises for unexplained reasons, the major culprit is normally a bad or overused infusion site.

Also remember Medtronic offers a wide variety of infusion sets. So talk to your Doctor to see whether you can test different infusion sets to see which one is best for you.

Know when to change your sensor.

Do not wait for the sensor to expire before changing your site. Remember that:

  • It takes nearly an hour to charge your transmitter.
  • It takes two hours for the sensor to warm up.
  • It takes 30 minutes for you to reenter Auto Mode after the first calibration.
  • The pump will require a mandatory calibration in 6 hours.

So if you start the sensor change-out at 7 pm, you will be up all night.

It also helps to “marinate” the new sensor about 24 hours in advance, but remember this might cut short the sensor life by a day.

Optimize your manual basal rates often for a rainy day.

There are days when you might not enter or stay in Auto Mode. So it is prudent to make sure your manual basals are good for such a time.

It also seems as if Auto Mode will “reset” if you run manual mode for a couple days. This has seemed to help where Auto Mode was delivering very little basal insulin.

Do not be too hard on yourself when on Auto Mode.

Auto Mode will test your patience on some days, but do not give up. Work with your doctor and Medtronic educator to optimize your settings. Also, be realistic on your BG targets when using Auto Mode. Auto Mode might not be for you if you are looking for tight control of your BGs.

I would say a realistic HbA1c when using Auto Mode is between 6.5 and 7.0.

Auto Mode Medtronic MiniMed 670G Pump Settings

Spike Control is Auto Mode’s Biggest Weakness for the 670G

Now that I have been using Auto Mode for the Medtronic MiniMed 670G for the last one-and-a-half years, I can say that spike control is one of the major weaknesses of this closed loop system.

Auto Mode does a decent job of controlling BGs for low to moderate glycemic index foods. But for high glycemic index foods, the pump struggles because of inherent Auto Mode safeguards.

As a safeguard against hypoglycemia, the pump pauses basal and microbolus delivery following meal bolus delivery for close to thirty minutes. This makes it very hard for the pump to catch up with a meal related BG spike.

In the photo snapshot, as soon as I bolus for my breakfast comprising a cup of tea and a piece of toast, there are purple dots dissapear for close to thirty minutes (purple dots signify every time the pump dispenses a microbolus or basal dose).

As you can see, there is a period of close to thirty minutes (green box) where the pump does not dispense microbolus or basal dose. In cases of high glycemic index foods, the MiniMed 670G cannot catch up with the runaway BG numbers.

According to Medtronic, this period of no microbolus or basal delivery is needed to determine the BG trend after meal bolusing.

Even though the pump resumes microbolus and basal delivery, it is too late and the BG spike is inevitable.

Waiting longer than the 5-15 minutes before eating recommended by Medtronic somewhat helps. But it is still hard to recover from 30 minutes of no insulin delivery.

The reason manual mode is so good with spike control as compared to Auto Mode is because manual mode allows for a good balance between bolus and basal. The user can be able to adjust the basal does just right to assist the meal bolus counteract BG spikes.

Auto Mode

Dawn Phenomenon and Auto Mode

According to Medtronic, Auto Mode does not learn an individual’s time of day patterns or diurnal variations (i.e., dawn phenomenon) for the Medtronic MiniMed 670G.

Medtronic recommends the following for dawn phenomenon (word-for-word):

Morning highs: Assess for overnight / bedtime highs first, bedtime snack with inadequate or no bolus, morning caffeine. If issue is identified as dawn phenomenon, have patient test BG, take recommended correction dose and bolus for breakfast at least 15-20 minutes before eating. “

SEe this medTronic document

The same would most likely apply for the Somogyi effect.

Basically for both the Somogyi effect and dawn phenomenon, your fasting BG reading are elevated in the morning due to peak production of the cortisol hormone (dawn phenomenon) or your liver compensating for low sugar at night (somogyi effect)

Read more on dawn phenomenon and the Somogyi effect and strategies for dealing with both at

Auto Mode

Finding success with Auto Mode for the Medtronic MiniMed 670G

Since Auto Mode is adaptive and conservative in nature, patience must be exercised and expectations curtailed to reasonable levels.

I can say it took me about a year to get to the point where I was comfortable with Auto Mode. And if you are hoping for a HbA1c of 5.7 with Auto Mode, it will not happen unless you are following a very compliant diet.

Realistically I would say that a HbA1c between 6.5 and 7.0 is easily achievable with Auto Mode without changing your pre-Auto Mode diet or habits. 

But here are some tips from my experience on how to be successful in using Auto Mode to achieve the realistic HbA1c goals discussed above.

Get the new Enhanced Guardian 3 Transmitter (Version 2.2)

A lot of frustration for many users with Auto Mode arose from the defective first generation sensor transmitter that made it hard to enter Auto Mode due to the infamous “BG required loop”.

Medtronic resolved this issue with their new enhanced transmitter. I must say that I have had a lot of success with this new transmitter.

Using the upper thigh as a sensor insertion site, the guardian sensor is very accurate and in my view comparable to the Dexcom 5 which I used prior to getting the 670G. The new transmitter makes the CGM sensor experience even more pleasant.

The enhanced transmitter is a good foundation to finding success with Auto Mode since the more accurate the sensor, the better the control. The less the number of incessant errors and alarms at night, the higher the chance you will stick it out with Auto Mode.

To request for the new enhanced transmitter follow the link below:

I received the following message when my Diabetes educator ordered my enhanced transmitter.

Know your carb ratio(s) and master your carb counting

Knowing your carb ratio is very important since this is one of the two inputs that Auto Mode uses to keep your readings close to the Medtronic advertised BG target of 120 mg/dL.

Just remember, with Auto Mode, you will have to dial you manual mode carb ratio by about 1-2 points. So if your carb ratio is around 10 when you are in manual mode, it is likely that your effective carb ratio for Auto Mode will be somewhere between 8 and 9.

Having carb ratios really off will result in the pump becoming overly aggressive or really conservative. Over bolusing causes the pump to cut back on basal and micro bolus. For me if I go for long without the basal or microbolus, I feel fatigued and have to always deal with a spike if I end up eating during these periods.

Under bolusing will obviously lead to highs that will make it hard for Auto Mode to stay on-track.

Periods of no basal or microbolus with the Medtronic Minimed 670G Auto Mode
Balance between Bolus and Basal – Periods of no basal or microbolus with the Medtronic Minimed 670G Auto Mode is marked by a lack of small purple dots on the sensor readout (dots signify basal/microbolus delivery).

Know that Auto Mode still requires discipline

Auto Mode does give you a little flexibility when it comes to your diet but it does not give you total freedom to do things you never did while in manual mode. For example, Auto Mode seems to get thrown off by constant snacking and bolusing. Constant bolusing really throws off basal delivery since the pump has to play a balancing act between basal and bolus to keep you within the 120 mg/dL target.

Similarly, Auto Mode requires mastery when it comes to eating foods with a high glycemic index or fatty food like pizza. It gets better with time but I normally exit Auto Mode and do dual bolusing when I eat such foods.

Do not try to trick Auto Mode

It is temping to give yourself a dose of bolus to correct high sugars under the guise of carb intake. Entering “fake or phantom carbs” really throws off Auto Mode.

Since Auto Mode assumes you ate with the bolus, it will continue to work hard to correct high sugars. What results is an accumulation of insulin that will cause your BGs to drop on the tail end of the insulin active time.

I have had scary lows at night as a result of trying to correct the high BGs right before bedtime outside Auto Mode’s recommended bolus.

Furthermore, the more Auto Mode keeps getting thrown off due to “fake carbs,” the more trouble you will have spiking and controlling hypoglycemic events.

If I must correct high sugars outside the recommended dose that Auto Mode suggests, I now exit to manual mode. Or else I just let Auto Mode take its time to getting me back on track.

Wait for 15-30 minutes to eat after Bolusing

I personally find waiting between 20-30 minutes helps with my post-meal spike control while in Auto Mode. The wait time is dependent on my pre-meal BG readings (longer times for higher BGs).

Auto Mode is not very good with Spike control as compared to manual mode and this can be a little frustrating. In manual mode, my basals and carb ratio are dialed down to a point where I have minimal spiking between meals.

Keep your Manual Basal up to date

It is important to make sure your basal patterns is still working well just in-case you have to exit from Auto Mode for a prolonged period of time due to illness or personal preference.

I am now making it a habit of exiting Auto Mode for two weeks every three months to optimize my basal patterns. This also seems to help my Auto Mode numbers.

This document by Medtronic for healthcare providers is the most detailed document I have read so far on Auto Mode and how to deal with different control scenarios.

Have a good Endocrinologist

Auto Mode and closed loop technology give us a glimpse of how complicated insulin pump therapy will become in the future. A good endocrinologist will keep up with the technology and help you fine tune your pump based on the training they continually receive from Medtronic or any other pump manufacturer.

As much as I hate going in to see my endocrinologist every three months, it has helped me achieve success with Auto Mode since it allows us to set  short-term strategies that can be evaluated during very visit.

Auto Mode Guardian Sensor Medtronic MiniMed 670G

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 learned 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.


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.


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.


Auto Mode CGM Sensors Pump Settings

Morning Meter Fasting Glucose is much higher than Sensor Glucose

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.

Article Review Auto Mode

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.

Bottom line: 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 the 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 setting is not used or explained for the trial).

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

Auto Mode CGM Sensors

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 of hours prior to replacing the current sensor. I have had mixed results with this approach.

Auto Mode Pump Settings

Solution for the Medtronic 670G AutoMode BG Loop

UPDATE 09/10/19 – A new enhanced transmitter to resolve the BG loop issue is being issued to Medtronic MiniMed 670G owners. This has worked beautifully for me since receiving it about 3 months ago.

To request for the new enhanced transmitter follow this link.

Or you can contact your Medtronic Diabetes Educator or call Medtronic directly for one.

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?

Auto Mode

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.