670G issues with basal rate

Hey guys,

I’ve had t1dm for 22 years (since I was 17), and have used a pump for 15 years. I’ve been on Medtronics hybrid 670g for about a year. I recently started a ketogenic diet (about 10 days ago) and I feel like the auto mode has not adjusted my nasal insulin enough…so despite appropriate mealtime boluses, I am hanging out in the 150s…and when I try to correct a bg of 150, it does not want to give me a correction bolts and so I have to cheat auto mode by pretending that I am bolusing for food…advice, thoughts?

Hi Alice @AliceD, I don’t use the 670G, I recently changed fron the MiniMed pumps I had been using for 15 years to the t-slim x2, but your experience sounds similar to what I found with the t-Slim. I’ve only glanced through the 670G user and training guides.

I suggest that you look at three of your settings [you said you have checked bolus ratios]: Target, insulin sensitivity and insulin duration. Two of the three are relatively easy to adjust, the insulin duration I find difficult to determine. Your target should be your first adjustment.

Unfortunately, the 670g target in auto mode is permanently 120, with an option to temporarily target 150 for exercise. The only variables are carb ratio, active insulin time, and meal choices/timing.

Having had to start auto mode three separate times, the micro boluses are always wimpy at the beginning. I think the best practice is to correct when above 150, and resist the temptation to bolus and not eat. Over time, the pump should slowly increase your micros as long as you aren’t going low.

There seem to be limitations based on one’s overall daily insulin usage. With the keto diet, you may be on the lower end of total daily dosage. The pump may improve over the next 4-8 weeks if you resist boluses without food.

This is definitely a time to seek more medical advice about your diet and settings, especially since being on a pump can increase the risk for DKA.

A lot of valid points are already mentioned.
here is another that no one has mentioned yet.

A lot of people do not realize that protein also does require insulin. Up to 50% of protein is slowly converted to glucose. So you may be bolusing enough for the carbs, but as you are now eating more protein (I am assuming, you are, as a lot of people do when cutting the carbs), your body doesnt have enough for the converted protein.

when I was doing low carb and eating more meat, I had to reduce my i:C quite a bit to cover all the extra protein. You may want to try that, or, enter more carbs to cover the extra protein. (though because it is slowly converted to glucose, you may need to try an extended bolus to make sure you do not go low. That slow - rise may be due to that slow conversion and not an inappropriate basal.

I also noticed that being low-carb, the effect of the insulin was much slower.

All food for thought!
Also if you plan on staying low carb for a while, I would suggest reading Dr Bernstein’s books, even if you do not follow his diet entirely. as his is also a low carb (but very stringent) he does have some good advice.
All the best!

Hi @Emet, your “ALL Food for thought” [my emphasis] really hit me in a nice way and got me thinking.
I too had observed how the carbohydrates produced from protein, especially from meat, affect me a couple of hours after a meal. At home I eat for supper a moderate - small piece of meat, fish or chicken but when eating out I wolf down the slab of steak or whole fish and often times did not count them in my carb calculations.

I’ve learned now to count more completely but I do NOT change me I:C ratio. I can “eyeball” the veggies, potato and other stuff pretty well for carb counting but for carbs in meat I may not have that down to a science - and almost always when eating out I use an extended bolus.

Hi Alice. I’ve been T1D for 42 years (since I was 16), been on a pump for 20 yrs, CGM for 10 and on the 670G system for about a month. The first couple weeks was VERY frustrating! Automode wasn’t doing what I thought it should (ie giving a correction bolus if I entered a BG of 200). I’ve had weekly conference calls with a Medtronic Trainer for the last past 3 wks and am finally starting to understand and trust Automode! Here’s what I learned:

There is more than a BG reading than effects a bolus correction. Your active insulin time and sensitivity do as well. So the reason it didn’t give me a correction bolus was based on the amount of active insulin I had. Sure enough, I got a down arrow shortly after that reading and came back into target.

I was all over the board with an average time in target at only 50% (compared to 63% before Automode!) Based on my Carelink reports, we made some adjustments to my carb ratio and active insulin time. This week’s report shows me in range for 81% of the last week!!

I strongly recommend talking to a Medtronic trainer. This was free of charge and really changed my experience. She also gave me tips on how to avoid the dreaded 12 hour calibration the day you start a new sensor. Good luck!

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Auto-mode is very slow adapt to changes like this. My advice, start exercising more to make up the difference. It will be easier to add an extra 45 minutes of exercise per day than waste your time fiddling with the insulin pump settings.

I too am T1 on Med 670 pump and have been eating low carb mostly keto for 3 months. After initial adjustment (withdrawal or candida burn off?) I now feel great and have found some delicious and fun food options. Much more stable bg too. Just want to add a couple things that might help you. 1. Watch out for the Dawn Phenomenon where bg rises for several hours in the am no matter what you consume. Took me along time to realize and now I bolus 2 g more and seems to work. 2. Eat red meat earlier in the day or eat less of it at dinner. The body is slow to metabolize it and you will get very high bg 3-4 hours later (overnight high). You can read all the science and evidence online and in Dr. Bernstein’s book. Good luck! Helene

Hi Alice,
Any update on this? Did auto mode “learn” your new patterns? I am having a similar issue with the 670G. I’ve only be doing LCHF for about two weeks and for the last 3 days I seem to be hovering around 155 all day and night. Have you found a way to correct this?