670 G Max Micro Bolus

I have been using the 670 for almost 18 months. I regularly trac the micro Bolus history on the graph. Until today, I have never seen it exceed 0.375. Today I saw it hit 0.425.

Does anyone know it there is a set max micro Bolus and if so, what it might be.

Tagging @rphil2 , who can probably help, and has been using 670 for a while.

There is a practical limit. I have never seen mine go above 0.425 either. The typical dose is 0.375 or less. I think the next jump would likely be 0.475 but to do that it would be pressing insulin at over 2.5 U per hour and I am doubtful that would happen.

If you like I can ask Medtronic and see if they know the set upper limit, but i suspect it is 0.425 since I would have rang a bell over that amount many times if I could have.

I have used the pump for about 24 months now and While I do not have every record, I do not see anything higher. Again let me know if you wish me to ask.

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things about Medtronic devices or the company. OK, they sent me a shirt and a cup but even I am more expensive than that.

I got a replacement 670 Pump a month ago and a new transmitter two months ago. Perhaps they have different algorithms because I got a 0.450 yesterday and again several times this morning, I never went above 0.375 on my old pump and transmitter.

I have occasional highs at night if I have a high carb meal. Accordingly, a 0.450 works to my advantage.

Are all of the 670 users here saying that even if you were to hit a bg of say 400, the pump won’t give more of a correction bolus than .450? What bg levels precipitate a max bolus? And how many of these corrections does it do in an hour, or 2 hours, or 3?

Micro boluses are delivered every five minutes and the dose is determined by the algorithm which takes into account current BG levels, the direction the BGs are moving, and I assume the rate of increase/decrease they are moving along with other factors.

I just checked back 30 minutes ago and noticed a 0.475 micro Bolus when my BG hit 219 (about 2 hours after breakfast) and again 15 minutes ago with a BG of 215. I also still have 2 units of insulin on board

No, it also gives a correction bolus and tells you to check connections etc. The auto bolus is on top of the suggested correction bolus. These are two different things entirely. The Micro bolus is the automated basal amount delivered by the pump.

Note: I am a Medtronic ambassador. My opinions are my own. They did not pay me to say nice things about Medtronic devices or the company. OK, they sent me a shirt and a cup but even I am more expensive than that.

Dave - I wanted to be sure you understood what the 670 was doing. Those micro boluses are the rough equivalent of an intuitive basal rate. That’s what isn’t going over .450.

You can give yourself a correction bolus dose if you have a BGL of higher than 150. This is calculated through the bolus wizard feature and takes into account the insulin on board and the micro boluses too. And you should…This will give you the appropriate bolus all at once to combat an existing hyperglycemic episode or prevent one from occurring.

Therein lies my complaint about the 670. At least one of my complaints. The fact that when the sensor detects you are going too high, the adjustments are so anemic to the point of users having to give themselves boluses, making what is purported to be a closed-loop feature nothing more than marketing nonsense.

1 Like

I agree. I think it’s the FDA more than Medtronic though. Or I hope it’s the FDA and not Medtronic being dopey. Though they’d never tell you if it was their fault. I’ve told the tech team every time I have called about the need for the pump to get more aggressive. They say they are noting this from a large constituency of customers and are working on the next version continuously. We’ll see I guess.

1 Like

0.450 units every five minutes is equivalent to 5.4 units every hour which, in my opinion, is fairly aggressive under “normal” circumstances. If you need more than that, then you have probably miscalculated your carb intake. The algorithm for the micro boluses of the 670 was probably not designed to cover user “mistakes.” For that purpose, the 670 includes a Bolus Wizard which allows the user to make Bolus corrections.

In my experience, the 670 has kept my BGs at acceptable levels as long as I have properly accounted for my carb intake. I know I go higher too often than I should, but it is usually due to poor food choices and miscalculating mealtime boluses.

Don, if high, I’d rather get my correction “up front”, ie at the time that the high is noted. Taking an hour to get about 5U of correction is not how I like to roll. :slight_smile: It seems apparent to me that there is a large contingent of 670 users unhappy with the algorithm.

I went into my pump menue and under options, clicked on Delivery Settings and found Max Basal/Bolus. I clicked on Max Basal/Bolus and found my Max Basil was set at 5.05 u/hr. When I tried to change the setting, I got a message that I should consult my medical professional before making any changes. However, I changed it to 5.5 and will see how that changes the max micro Bolus when in auto mode.

Been trying to understand the algorithms. After breakfast I had a steady rise in BS (Sensor values) even though I took a large dose for breakfast. When reaching 360 mg/dL(I am in Sweden and we mmol/L and the value was around 20), I checked the microboluses and still only giving me 0,125 units (per 5 mins) as the highest (as far as I can remember I have never been given higher than 0,150). I had to give a correction of course - calculated as to 2,6 units. [I weigh 80 kg approx, 175 lbs and have a pretty good Hba1c]

Is there anyone that has any inkling on how to increase the micorbolus-dosage? I go crazy with how low doses it gives me when reaching high levels. Anyone has been able to break into the algorithm or found any Admin privileges to change this. It is a fantastic piece of machinery but its anxiety is really giving me a headache.

Take care now!

0.125 seems to be fairly standard for me. However, after checking yesterday’s activity I noticed one micro Bolus was 0.275 units when my BG was at 175. I also once recall seeing a micro bolus of 0.750.

To supplement the micro boluses, I often use “fill cannula” which I have set at 0.8 units.

1 Like

Welcome to TUD, Andeas, hope you stick around!

When I was using the 670G this was a huge frustration for me, and I think still is for a lot of people. The one parameter you can control that has the greatest effect on this is AIT, Active Insulin Time. Supposedly it’s the actual insulin effect duration, but bears little relation to what you’d set it at for a standard pump. The logic is that a shorter AIT permits a larger microbulus without the algorithm thinking you’re “stacking.” I set it to the lowest possible value, which was 2hrs, and that helped make the pump more aggressive about correcting highs, but still left me frustrated.

The other issue is that it uses a higher target for determining corrections than for general operations. Standard algorithm target is 120 but it uses 150 for corrections, then the standard algorithm kicks in and is supposed to take you the rest of the way. But it’s v-e-r-y s-l-o-w. This is not an adjustable parameter.

Generally the people who are happiest with this pump are the ones who were struggling to get down out of HBA1Cs in the 8s or worse. It’s supposed to get you into the sixes and a higher time-in-range. Before I started using it I was already getting 6 or lower HBA1Cs and 90% TIR, which the 670 couldn’t match. So I went back to my old pager-style Paradigm and Dexcom CGM.

1 Like

Thanks. I kind of figured something along these lines. And I totally agree; it is soooooooooo slow.