Upgrading from 530G to 670G: Why the Larger Reservoir

In the very near future (less than 2 months) I plan on upgrading from the 530G with Enlite CGM to the 670G with Guardian CGM. I have done tons of research on the new features and capabilities of the 670G, the most significant being, of course, Auto Mode. I also noticed, however, that the reservoir is 300 as compared to the 180 used by the 530G. This is more than 1.5 times as large, and if I were to use the exact same amount of insulin per day would obviously mean changing my pump much less often (definitely a desirable thing!). Do the significantly different methods and algorithms used with Auto Mode mean that I will be using more insulin, or will I really get to change my pump less often?

A few years ago I changed from a pump with a 2 mL reservoir (Animas Ping) to one with a 3 mL reservoir (MiniMed 722). I didn’t want to change the frequency of infusion site changes due to a slow down of site absorption but I could reduce the frequency of insulin cartridge changes. So, my cartridge and infusion site changes are now independent of each other.

I fill the cartridge with about 300 units of insulin and only change it when it runs out. I do change the cannula portion of the infusion set every three days. I change the infusion set tubing on the same schedule as the insulin cartridges.

This way, my cartridges last about 7-10 days and I don’t have to buy as many of them. I also like that I don’t need to do a complete cartridge/tubing/site change every three days. It cuts down on the overall work load. I sometimes wonder why it took me so long to catch on to this!

There have been articles about pump set occlusions being caused by running insulin, particularly my insulin, Apidra, for so long in a single cartridge/infusion tubing setup. In 18 months I have not had a single occlusion from this practice.


In the 670G you can also put in the small reservoir. So why compline.

I moved from 530 with the small reservoir to the 670. I’ve heard of people using the smaller reservoir in the 670. I use the larger reservoir and only fill it with the same amount as I did in the 530 which is about half full.

it makes the pump larger. so that’s the “complaint”. Is that not a legitimate complaint? To be forced to use a larger pump because MM won’t make 2 sizes? Sounds legit to me!

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IMO, the smaller the better. Something I wear 24/7 I want as small and as light as possible. Forcing me to “upgrade” to a larger model is not something I take kindly to. I’ll keep my 551 for as long as it is working

I totally agree and that is one of many reason why I do not have 670 anymore. I was referring to what I thought was her concern of having to use more insulin. And whoever responded “why complain” I think was inappropriate and disrespectful to the person with a question.

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I didn’t hear anyone complain, I only heard a question.

@njsokalski I do not have an experienced answer to your question as I have not made the switch to the 670 but I doubt there will be a large change in your insulin needs. Maybe some of our members that have made the change can weigh in on any differences they have noticed in their insulin needs.

In the past Medtronic has chosen to make pumps in two sizes 1.8 ml and 3 ml. Who knows why they chose to only make the 670 in 3 ml I doubt it has anything to do with needing more insulin.

Cost of 2 machines is to high and to have 1 machine saves also the FAA costs.

I don’t the think the FAA has jurisdiction over medical device certification. LOL!

it cost money to get approval for 2 machines.

FDA will ask a lot of money.

That doesn’t make a lot of sense to me. The difference between the large Reservoir and the small Reservoir is so miniscule as it relates to getting certification that it sounds like you are making this stuff up

Is the fact that the 670g is only produced in one size a problem? The 670 does not have to be filled to the max each time, it can be filled to any level up to 300 units. The user determines how much to put in it. That makes it suitable for almost every diabetic.

I have never understood why they made their previous pumps in two sizes. Was it for the sake of physical pump case size, in previous version the 180 unit versions were slightly shorter than their larger cousins, the difference to me did not seem like something worth shaking a stick at. The difference seemed petty and was not an issue that would drive me away. I suspect that Medtronic realized this and saw no reason to continue running near duplicate production lines.

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For the older models, medtronic makes 2 physical different pumps, for example 523 (180ml) and 723 (300ml). The 723 is physically different size and parts to drive the larger size reservoir. So I could guess each model had some degree of additional costs, and FDA review.
I think the 670 is physically one body. But you could put in the 180ml or 300ml (or whatever it is) into the same pump.

Below is link to physical dimensions.
It notes the 723 can use either 180 or 300 ml reservoir.
I think the smaller 180 was for kids ands folks with low TDD. I have always used the smaller 5xx models and one week of insulin is just about 180.

So the new 670 is likely be similar to the 723, and could use either size reservoir. But if, like me, only need 180ml, the larger 670 pump would be bulkier in my pocket.


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Prior to my current 300 unit reservoir pump, I had always used the smaller 180-unit cartridge. I’ve found filling my reservoir with 300 units and initiating two refresh cycles, one for the cartridge/tubing. And one for the cannula/site. The latter one I do every three days and the cartridge only needs changing every 7-9 days. It is easier to do this in the long run. I like it.

You’re right, the physical size difference is marginal.

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I suspect that from a marketing point they asked themselves, will offering only one size cost them any customers, my guess is the answer would be few if any.

Had they never produced the smaller pumps the size question would most likely be a moot subject.

But for me, will be a reason (among others) that I switch to another brand.

So even if they made 2 sizes, I’m likely to switch next time anyway.

I suspect that you and a relatively small number will be an exception rather than the rule.

FWIW I changed to a different pump at my last change but it was not because of physical pump size.

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I switched to the 630G last year which also takes the larger reservoir. I smaller ones will also fit, so I just used those until they were gone. As someone else mentioned, I fill the larger reservoir with approximately 6-7 days worth of insulin and change the cannula after 3 days. You will easily get used to it.

It is my understanding that it is the AA battery (instead of AAA) that requires the increased size, not the size of the reservoir. I have no idea why they increased the reservoir size.

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Do you think the fact that they’re using a color screen is the reason they had to switch to a larger battery? I hate that they have made the newer MiniMed pumps larger. My 551 is so simple to operate I don’t even have to hardly look at the screen to do many functions and it’s so quick to get to those functions.