I have an ongoing problem with bubbles forming in the reservior.

I have been a Minimed pumper for the past 12 years. This problem suddenly started about 5 months ago. The reservior would be bubble free on fill - after 12 hrs bubbles would appear and gradually grow to 1/3 volume at which point I would have to replace the reservior and infusion set.

I complained to Minimed and was told that I was doing something wrong. The local Minimed Rep monitored me filling reserviors and confirmed that I was following correct procedures. This problem is not confined to a single resevior or insulin batch.

Does anyone else have this proble?


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As with Natalie, I got my first pump in 1999 and was trained to slowly move the plunger up and down in the reservoir first (spreading lubricant). After doing this for 4 yrs. with the first pump, I have been doing it ever since. Never had any problems with larger bubbles that I know of, and could alway find another reason for a sudden spike in BG that happens occasionally. Also, as with Scott, I always inject equal air into a vial of insulin before withdrawing it into the reservoir.r

I have been on the pump for 1 month. The first few weeks, no bubbles. Then, the last two weeks, tons of bubbles where one night my sugar was sky high due to air bubbles in the tube.

I called Medtronics who walked me through refilling the reservoir and I am doing everything correctly including insulin at room tempurature.

They tried to think of everything possible...changes in temperature, pressure, etc...I am getting frustrated as this is a big problem.

There are NO BUBBLES when I fill the reservoir but don't know what is going on.

Didn't know about the ring thing due to cheaper production cost.

Good to know since my 90 days is not up yet!!!

How old is your insulin vial? I always find that I get fewer bubbles when starting a new vial. It has to do with the air-pressure inside of there.

When you go to fill the reservoir, you should first inject a certain amount of air into the vial, then draw out an equal amount of insulin. It's the same way I did it with syringes way back in the day... this makes sure the air takes the place of the insulin you're pulling out, and the inside of the vial isn't under constant pressure.

I find that, inevitably, with the crude unit-markings on the reservoir and the constant pushing of air-bubbles back out of the reservoir (and the occasional air leakage at the O-rings), I always push more air into the vial than insulin I end up pulling out. I push in air to just shy of the the 1.8 mark (180 units), and by the time I'm done trying to push air bubbles out of the reservoir and back into the vial, I'm at 1.4. That's 40 extra units (of air) in the vial that has nowhere to go.

This ends up putting positive pressure in the vial, and the air (and insulin) end up compressed in order for it all to fit in there.

When it's moved from one place to another (i.e. a reservoir, where one end - the plunger - is moveable) the contents expand to their natural volume and might even push the plunger out ever-so-slightly, causing the tiny air bubbles to get larger.

It's just a theory, and without some scientific equipment (which I don't have), there's no way to really know for sure. But if this happens more with used than new vials, it's likely the culprit.

Try this, especially if it's an older vial: hold the vial right-side up, and attach the reservoir. Pull out 40 units of air (this number is a guess). Take the reservoir and the blue cap off of the vial and use the plunger to release the air into the room. This will lower the pressure inside the vial, and it might help.

If you feel the plunger getting "pulled back" into the vial, that means there's negative pressure/not enough air in there. If, when you try to push air into it, the plunger wants to pop back out on its own, there's positive pressure/too much air. You want to be somewhere in the middle.

Does this make sense? I'm trying not to be too scientific...

I have always used a similar procedure to fill the resevoirs.

The problem started with the NEW reserviors - They do not have as tight a gasket fit as the old model.

Bottom Line - MiniMed needs to acknowledge that there is a problem, provide a temporary workaround (if necessary), and then fix the problem.


Hi Jodil:
I am so frustrated with bubbles that appear around the 'O' ring and after a few boluses become a big bubble that makes my blood sugar go high.

The problem started last year with the NEW model reservoir. The gasket on the new reservoir is not tight.

I have changed pumps, reservoirs, and insulin. Same problem. I even had the local Minimed rep monitor me filling reservoirs.

Medtronics needs to solve the problem. We cannot be the ONLY users with this problem.


There's another company, Fifty50 Medical I think they're called, that also makes compatible reservoirs. I wonder if any Tu members have tried them and if they're any better.




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