Tandem T-Slim X2: I am having to change the site more often than I used to

I have been on the Tandem T-Slim X2 for over a year. I have been on the closed loop system with the Dexcom G7 since June.

Sometimes I've had great periods of results. I've occasionally had days 100% in range. Recently, however, a terrible thing has been happening where I have unexplained highs by the third day of an infusion set. This makes my life more stressful because if I am travelling about, I don't know if I can trust the pump to work by day three.

I am careful to check the site and I try and move them around a lot. Do sites stop being able to absorb insulin after a certain amount? I have noticed after large meals (with large doses) I sometimes have to change the site early.

Here is what happened today. I woke up on a reading of 7.8mmol/L. After a shower it rose to 8.8. My breakfast was about 30g of carbs so I put that into the pump and dosed for it. By the time I sat down for breakfast it was 9.5mmol/L. Two hours later it's 16.6mmol/L, and this is after Control IQ raised the basal and gave me a correction dose an hour ago.

So basically I have had a completely normal morning and I'm sitting here on a reading of 16.2mmol/L for no reason. This isn't supposed to happen on the closed loop system after a small meal.

Hopeful34 said:

Which cannulas are you using @RobertJ and do you use extended bolus at all?

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I am using the plastic ones, or basically the ones that aren't steel. My levels have remained about 10mmol/L even eight hours after they rose. I've changed my infusion set an hour ago but nothing has improved yet.

I actually think this was an issue with bubbles in the tubing. I think I'll be more careful with how I load the syringe with insulin and how I extract air from the cartridge.

Saying that, I'm not yet sure my recent site change has worked. I am also not yet confident I'm going to successfully resolve this wider problem. It would be great to get back to a full three days of the pump working well though.

Hello, @searley. I am on Novorapid.

I should say, things have been normal again since I changed my site. I think it was an issue with bubbles. I read the manual and watched a video on changing the infusion set, and I think I need to be a bit more careful with this process from now on.

Perhaps I spoke too soon. Even after a site change, I am experiencing another three-hour high (and counting) after a meal. I had a cooked breakfast at a cafe with two cappuccinos.

I began on 5.8mmol/L, so a good reading. I must have underestimated everything but three and a half hours after starting the meal my Dexcom says 14.4mmol/L and a finger-prick test says 13.3mmol/L.

This is supposed to be the closed loop system. It's supposed to be an artificial pancreas! This doesn't seem right.

Chas C said:

I can have these issues (on odd occasions) and I'm pretty sure its site related, I rotate sites using my stomach and find that I can get just about 1 month on each side so each side gets a months rest. If I get a bleeder and forget then even after a month going back to same location can cause issues. I'm pretty strict with rotation order as my legs suffered badly in the 70's and 80's when I took no notice.

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Thanks, @Chas C . I think my problem has been more to do with changing the infusion set rather than overusing sites. I think in recent times I haven't been careful enough removing bubbles. For example, it was only recently I discovered that you're supposed to put the pump upright when you fill the tubing. This is because, when I first got the pump, I didn't bother reading the instructions. I had some lessons from my diabetic clinic and wrongly assumed that was sufficient.

I have another question for fellow users of the T:Slim X2 who are on a closed-loop system with a Dexcom G7.

If your blood sugar goes above 13.5mmol/L, how long does it take to go down? I ask because, once it goes above around that level, it seems to be guaranteed that I'll be high for three hours minimum. Is this normal?