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.

Insulin Therapy Pump Therapy

Two Must-Have Books for people on Insulin or Pump Therapy

When moving to pump therapy, the idea of basal and bolus and how you use them in tandem does not make a lot of sense at first. There’s little to using long acting insulin such as Lantus than just injecting and letting it do its thing as far as your basal insulin is concerned.

But since your pump uses a short-acting insulin, you have to supply your basal insulin very small doses to mimic a long acting insulin 24 hour dose.

Getting your basal pump settings tuned is the foundation for successful pumping. In most cases you will need more than one basal rate to deal with uneven insulin requirement in the course of the day.”

The following two books have been indispensable books for me as I have tried to set basals, carb ratios, active insulin time etc. When I was first diagnosed, I struggled a lot with severe hypoglycemia.

“Think like a Pancreas” is probably the best book out there for optimizing your pump settings.

But reading Gary Scheiner’s book, “Think like a Pancreas” was just an eye opening experience. (See it on Amazon). This is the first book I would encourage anyone considering pump therapy or having trouble with BG control with their pump to get.

It might be the only book you will need to get up and running. Gary offers a myriad of real life scenarios and chances you’ll find a scenario that fits your case.

But if you want to delve deeper into the intricacies of the Insulin pump therapy, “Pumping Insulin” by John Walsh and Ruth Roberts will do the trick.

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.

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 Pump Settings

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 - 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. That is why it is important to work with your endo or educator to tune these settings.


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 (CR) and Active Insulin time (AIT).