Pump question

This is what I don't understand about operating a pump:

If I deliver a giant syringe bolus (to counteract DP, for instance), the large amount of active insulin is going to decrease my BG faster than a small pump correction, correct?

I deal heavily in corrections because I am not able to do good predictions. I have a lot of variation and a lack of predictable patterns, even when I do a lot of controls. Assuming a small pump correction bolus is active over the same time interval as a large manual injection correction bolus, then you are waiting 4 hours to see the effect of a minor pump correction, correct? When I deliver a large manual injection, I can see the activity of the insulin in my data very clearly because its a large magnitude event. If the magnitude is very small, I don't think I will be able to see it and I wont have any info about whether I dosed correctly.

What is the benefit of dosing small corrections over a large time interval, instead of doing it all in one shot? I see negative consequences, but am unable to identify what the benefits are. I may not understand.

Sorry, LBREP, this gets a little wordy and may not be clear. Its good practice for me to talk to about this stuff because it might help me express myself more clearly. I think I have difficulty 'using the language of diabetes."

It sounds kike you are confusing basal and Bolus. There is no reason you can not administer the same amount of insulin with a pump as with an injection. Your Endo can help you estavlish the correct Basal amount for the pump. The Bsal mimicks the Pancreas to give you on going background insulin and you Bolus enough insulin to cover what you eat.

I am really unclear what you are asking. You can do large boluses with a pump. How large are you talking? Also the pump boluses seem to be more effective then injections.
With a pump you have more control so people tend to do smaller corrections more often to fine tune their BG.

If I spoke to 300 though I am delivering a 10u bolus through the pump. If I am just going a little higher it’s small doses.

Maybe it would help if you provided BG numbers and patterns of things you do. You mention lack of predictable pattens, well that’s one reason to do smaller corrections.

I do find it a little confusing because there's only one insulin in a pump. I define basal as the 'baseline' dose. Any insulin that's delivered to supplement the baseline, correction, or meal insulin, I think of as bolus. Is that how you understand it?

The pump covers both basal and bolus insulin. All with rapid-acting insulin. It gives tiny amounts of insulin every five minutes to cover your background insulin, taking the place of your long-acting Lantuss or Levamir (and doing so in a much more accurate, personally-tailored manner). Then you also can do boluses of however much insulin you need to cover meals or make corrections after meals. The pump also makes the calculations for you of how much insulin you will need based in your BG and carb count. It also delivers fractional units of insulin rather than whole units like a pen, so you can get a much more accurate insulin delivery with far less threat of highs or lows. The newer pumps also offer integrated Continuous Glucose Monitors,no you can keep a good eye on your BG all day long and get constant feedback. The pump is the best decision you could ever make for long-term health.

If I deliver a giant syringe bolus, the large amount of active insulin is going to decrease my BG faster than a small pump correction, correct?

No, I do not believe that is correct. I think it actually works the opposite way.

What I am referring to here is how quickly a bolus amount of insulin will be absorbed into the blood stream. This is what I believe determines how quickly the insulin will start to lower your BG. I don't believe it matters whether the bolus is delivered with a syringe or through an infusion site.

A smaller bolus will be absorbed more quickly and have a more shallow "peak" than a larger bolus. My guess is that this is true, at least in part, because of the consequences of the differences in the "surface area to volume ratio". A larger bolus volume will have a smaller surface area relative to that volume than a smaller bolus. This means it won't be absorbed as quickly.

But the larger bolus will take more time to be absorbed (lasts longer) and the peak will be both later and higher than the smaller bolus.

At least that's how I've always thought about it.


Sorry, Seth. Bummer. I'll try again. My fault, I don't think I am able to express myself clearly. Yes, I understand that one CAN do large boluses with a pump, but then, what is the benefit of a pump over manual injections? I think that you all are delivering 'temporary basal' when you have an identifiable, baseline pattern that demands more or less insulin. So, an increase/decrease in insulin requirement that occurs predictably at the same time of day, or always occurs after a particular activity. Is your pump's insulin delivery programmed more based on time of day, or more based on events?

I think I am dosing more, based on the occurrence of particular events, like exercising. I wondering if I am having erratic patterns because I have erratic behavior. Maybe I need to do the same thing at the same time of day, everyday. Is that what you do?

Seth, what do you mean by "pump boluses seem to be more effective?" Do you mean that they happen faster or that you require fewer units of correction?

I do see some patterns, but they may only last 2 to 6 weeks. If my Doc makes all the necessary adjustments in my pump basal, then she's going to be chronically overworked. I think I have to be able to do it. An adjustment every three to six months, coinciding with my Endo visit, isn't gonna cut it. Are you interpreting your own patterns, or is your Doc, or are you/your Doc using software to analyze the necessary adjustments? I just don't understand how this is supposed to work, at all.

Agreed that this at least seems like a confusion of basal (small increments over long time) vs bolus (big dose for correction or carb intake), I'd just add the footnote that pump settings generally include a bolus limit, which may be set quite conservatively when you first start out. I think the setting was like 10 units on my Medtronic. But you should be able to change those to suit your needs.

It gives tiny amounts of insulin every five minutes to cover your background insulin, taking the place of your long-acting Lantus or Levemir

You can't assume that there will be a 5 minute interval between basal doses. The pump will compute the actual interval between basal doses and the amount of each basal dose based on what "Basal Rate" has been specified for that time period.

If the basal rate is "high enough", then, yes, the interval may very well be every 5 minutes. But if someone specifies a low basil rate, it will be less.

An example. My current pump's lowest dose is 0.025 units. If I specify a basal rate of 0.1 units per hour, then there will be four 0.025 unit basal doses during the hour with 15 minutes between each one.

Basically, on my pump, any basil rate under 0.3 units per hour (12 * 0.025) is going to have more than 5 minutes between each basal dose.

While I haven't checked so I don't really know, it's also possible that an interval shorter than 5 minutes could be used for larger basal rates. For example, my typical basal is 0.6 units per hour. For all I know my pump may be implementing that by delivering 0.025 units every 2 1/2 minutes. I think it would actually make more sense to do it that way.


I live in the realm of 12 unit correction bolus and I doubt that I will ever be able to fine tune to a level of fractional units. I am REALLY far away from that.

There's no way I'll ever use the meal bolus calculator. I think I dose a lot more on intuition now, than I ever have before because I am making a best guess on what my BG is going to do next - based on: 1.) if there's active insulin; 2.) what the Dexcom sensor reading/behavior is; 3.) what I anticipate is going to happen next. I find the pump calculations somewhat unhelpful. Even with IOB calculator, my complaint is that sometimes I am dosing so that I have high IOB, to counteract highs that I anticipate. The pump doesn't know what I'm about to do, so I don't really trust it to do all these calculations. But, I'm not doing that great on my own (maybe 30 - 60% in range).

O.K., thanks a bunch. That feels a little counter intuitive. Thanks for clarifying on an important point. I'll have to think about it more.

When I was last on a pump, I overrode all the programming to deliver as close to manual injection dosages, as possible. I had a lot of severe lows. Maybe there's a connection there. Big whoops. When last on a pump, I was also operating from a paradigm in which diabetes was much more of a deterministic system than I now understand it to be. I think that I assumed that my blood sugar was flatline until proven otherwise. I didn't have a sensor when I started on a pump. When I got a sensor, there was a paradigm shift because I could easily see just how dynamic the data was. I don't know if I will be able to 'intellectually' make the transition to the pump. I do not trust my pump. Maybe that is the problem.

The pump basal is the equivalent of the lantus or other day-long insulin you take in the MDI regimen. But it behaves more like a normal pancreas would, in that it's putting out small amounts on a continual basis (which you can fine tune to your metabolism) rather than one larger dose of something that's been pharmaceutically tweaked to last a long time.

But I DEFINITELY take the point that there isn't some rule commanding Thou Shalt Use A Pump. It's not necessarily the answer to all T1 lifestyles. After a long acclimation I do find the pump marginally easier to live with. But MDI was SO much better than R/NPH, which I was on for far too long, that to me THAT was the life-changer, and the pump is more of an incremental improvement, not without its own drawbacks.

Re the surface-to-volume issue: When I was being trained on the Medtronic they explained that this is why the pump pushes boluses out gradually rather than all at once (not to be confused with the basal increments--the time interval is over less than a minute). I assume most pumps do it this way, e.g., the Snap, which I just changed to. I don't know if this totally obviates the problem but it has to ameliorate it more than what happens with a syringe, which squirts it all into you in a single blurp and the insulin can just pool in one spot under the skin. (I remember getting contradictory advice about whether you should rub those out or let 'em sit there when I was on MDI.)

Big bolus has less predictable absorption rate? hmmm...I see. I understand. Thank you.

Basal settings are supposed to conform to your basic metabolic pattern independent of things like exercise--you don't want to program it for that stuff. You'd do a lot of testing over the first few days while not exercising a lot or eating high-carb meals etc. to determine what those settings should be. Your endo would supervise all that pretty closely at the start but you can tweak the settings yourself as you get more comfortable with the whole process. I do mine--for instance I haven't been able to ride my bike for a couple of weeks due to the incessant blizzards we're having here in Boston, so all my rates are having to creep up (goddamit!!!) to account for not getting as much exercise. It's only a temporary problem (it BETTER be only temporary!!!) but it's long-lasting enough to be worth doing some tweaks. That seems kind of analogous to what you're talking about maybe.

There is only one kind of insulin an a pump, but its delivered for different purposes. The 24/7 "drip" of fast-acting insulin is defined as the "basal", and while it technically works differently than injected basal/Lantus because you're getting a constant drip, the effect is the same because every 5 minutes you get 1 drop of insulin that lasts for 4 hours, but in 5 more minutes you get another tiny drop and so forth so that you get around-the-clock coverage without a peak.

Everything else- all meals and corrections are covered with the same kind of insulin but as a single instance of a lot at once, and thats the "bolus" insulin.

I think thats just a different way of explaining what you already said, the difference between "basal" and "bolus" insulin in a pump is equivalent to using a single can of paint on both a door and a wall, but referring to the paint on the door as "door paint" while the stuff on the wall (although exactly identical) is the "wall paint". Their naming refers to their action and intended use, and not its chemical makeup.

Back 8-10 years ago I think there were two pump companies each claiming to have the better delivery system because one company (and I don't remember which two it was, probably Medtronic and Animas, but it was a while ago) "delivered a tiny personalized increment every 5 minutes" while the other "delivered a precisely calculated increment as often as needed" (or something along those lines.

Its the difference between doing math to determine that you need 1 unit of insulin every hour, so divide 1 unit by 12 (the number of 5-minute increments in a hour) to determine you'll be getting ~.083u/5minutes; versus doing math that says you need 1 unit of insulin every hour, so if the pump delivers in .05unit increments, you'll be getting ~.05u/3min.

Since the math in the end is that you get a bunch of tiny doses that over the course of the hour equal the same thing, its a mute point unless you need such teeny tiny doses that the minimum rate/hour possible is too small.

Yeah, my basal needs increase come morning, although they are not the same day to day. Sometimes I need 12 u of correction mid-morning and some days I need no correction.

I think the bolus correction actually is effective over four hours, where a shot is kind of all at once.Someone correct me if I'm wrong. Or maybe your basal needs adjusting. Here's hoping you get it straightened out. I know it can be frustrating. Keep trying.