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

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.

Basal Settings

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 to 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 talking about how basals are the foundation of successful pump therapy.