Questioning Pump Delivery of Basal Insulin

For the last three days my blood sugars have been very high. In response, I have increased my basal insulin by 10% and given myself a meal bolus at each meal but then eat only a fraction of the carbs unless my blood sugar is low or what I expect based on IOB. So after every meal if my blood sugar is either fine or trending low and I will either eat more meal carbs. But if it is high I will not eat the rest of the carbs I put in as a bolus. Over the last three days BG just keep going up and up after the bolus is gone. This despite increasing the basal rate.

This afternoon I finally determined what has been happening is consistent with the pump not delivering basal insulin at all. BG is high and then I take a meal bolus and it comes down. After the meal bolus is done it goes back up and does not come down until the next bolus.

I know the pump motor is working as the bolus is working. Is it possible that for some reason the basal insulin is not being delivered and yet the bolus insulin is? I thought that an impossible situation but it is the only thing that explains my last three days.

Thanks. Can anyone share their thoughts?

Sorry meant not delivering basal insulin

One possibility is air bubbles in your reservoir and tubing, or poor absorption at site. Has this continued to happen through several changes?

Over the last three days I changed the insulin three times. So unless air bubbles in all three, it must be something else. Do you think basal not being delivered is a possibility?

Of course it’s a possibility! Anything is possible. I assume that you have been delivering your bolus through the pump. If so, then the pump software has developed an unusual glitch. Phone the pump manufacturer’s Customer Service.

I agree if you think the pump is not working correctly, call tech support. They will have you do all kinds of checks to make sure the pump is functioning.
And just a side note. Over the years, this has happened many times. All of a sudden, insulin just doesn’t seem to work. I make some major adjustments that need to stay for a few weeks and than things work back down. Who knows, infection, hormones, weather. Can’t always find an answer but I push more insulin and sooner or later things start working back down again. The joys of diabetes. No rhyme or reason sometimes. But also long as you have changed infusion sets, and sites and insulin bottles, it just might be who knows. Calling the pump company such be first thing.

Perhaps you need to increase the basal rate or the insulin to carbs rate.

You could test this by disconnecting, and set a very high temp basal. Within a few minutes you should see some insulin come out, but not into your body.

Under utilities, you can see amounts of basal and bolus the pump thinks it delivered each day.
(For medtronic pumps)

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what model of pump?

I have a Metronics 723 and also an older Medtronics 523.

I disconnected the 723 and set a temp basal of 10 units per hour for 30 minutes. I waited 15 minutes and didn’t see a single drop. At first I thought that proved the 723 was suddenly defective. But then I pulled out my old pump and didn’t see a drop either. They can’t both be defective.

How often is the basal supposed to be delivered? I though it was every five minutes but it could be more or less frequently. I thought 15 minutes at a rate of 10 units per hour for 30 minutes would have been plenty of time to see a drop.

You should see insulin, but it does come out in small increments. So if end of infusion set was set on table, you would see the accumulated amount. But if you were holding the end in the air to observe it, you may not see each tiny pulse.

Is bolus working ? If mechanical problem, seems odd if bolus works but not basal.

I suggest you contact medtronic support.

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Have you tried clearing everything else out of the equation. I have had this happen a couple of times over the years. My usual reaction was to assume the pump was not delivering my basal. The best I could do to fix the problem was to:
1 - Change my site. For me, my site last 3 days. Sometimes 4, sometimes 1.
2 - Don’t just change the insulin in the cartridge. Change insulin bottles. Could yours have gotten too hot, too cold, too old?
3 - Fast for the day. Clear out any possibility of slow absorbing carbs, missed carbs etc.
4 - Now that the basal should be isolated as the only variable, if you are still having problems, call the pump manuf.

Side note - How is your life treating you. There is a a good side discussion on this site about how stress raises some people’s BG up to 200 points. Best of luck to you and I hope this helps

Thanks everyone for your help. I got a replacement Medtronic 723 this morning. Called them yesterday. So I will see if situation improves.

Have read all the literature that Medtronic has to offer. Have not found out exactly how often we should see drops…how often the basal insulin is delivered. Is it every minute, every 5, every 20?.. Does anyone know for sure the delivery frequency?

Disconnect from your site and place the delivery end of the tube on a tissue. Run basal delivery. If it is functioning you will clearly see the insulin droplets gradually accruing on the tissue.

I found the following explanation, which I believe is consistent with what a medtronic rep told me a long time ago. The “gear” mechanism that pushes the insulin though can deliver a specific amount with each “turn” of the motor. It either delivers .05 (fast) or .025 (slow) per turn/delivery. So the pump determines how often to “push” to deliver your rate, and adapts as your basal rate changes. Children with lower basal rates/hr would tend to trigger the slow mode. (I think older pumps only had one mode).

(Following is from another source)

If your setting is 1.9 u/hr, the pump will deliver in 0.05 unit amounts. 1.9 units divided by 0.05 doses is 38 deliveries over one hour, or 0.05 units every 1 minute and 35 seconds.

For 2.9 u/hr, the pump will still deliver in 0.05 unit amounts. 2.9 units divided by 0.05 is 58 deliveries required over the hour, or 0.05 units every 1 minute and 2 seconds.

For people with basal rates under 1.0 u/hr, the pump delivers in smaller doses of 0.025 units. For example a setting of 0.6 u/hr divided by 0.025 is 24 deliveries over the hour or 0.025 units every 2 minutes and 30 seconds.

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