Ask D"Mine: How Insulin on Board (IOB) is Like an IOU

http://type2diabetestreatment.net/diabetes-mellitus/ask-dmine-how-insulin-on-board-iob-is-like-an-iou/

If we had a dollar for every time "What the heck??" was uttered in managing diabetes, we"d probably have enough funds to find the cure ourselves! Luckily, we thrive on the never-ending mysteries of diabetes here at our weekly advice column, Ask D"Mine, hosted by veteran type 1, diabetes author and educator Wil Dubois.

This week, Wil offers his two cents on how insulin on board is calculated and how we can even think of it like a little gift, and some tips on dosing for a lower-carb diet.

Need help navigating life with diabetes? Email us at AskDMine@diabetesmine.com

Terry, type 1 from California, asks: Should insulin on board be subtracted from the full bolus (correction + carbs) or only from the correction bolus?

Wil@Ask D’Mine answers: Awesome question, but before we dig into it, we need to lay the groundwork for everyone else. Insulin on board, or IOB is simply insulin still working in the body from a previous bolus of fast-acting insulin. IOB can be “left over” insulin from either previous corrections or from meal boli.

Why does it matter? Well, the concern is over the “stacking” of insulin, where consecutive corrections or meal bolus doses can layer on existing action curves of insulin that can overlap, leading to low blood sugars. Of course, in a perfect world, we wouldn’t need to worry about IOB at all. Every meal bolus would have exactly the right amount of insulin to cover the carbs in the food. Every correction bolus would bring us smartly back down to target. So what’s the big deal?

Uh… In case you didn’t notice it, we soooooooo don’t live in a perfect world.

When it comes to meal boli, even the most careful carb counters often get it wrong, and a host of environmental factors can actually alter your body’s insulin-to-carb ratio throughout the day, even if the count itself is perfect. When it comes to corrections, billions of unseen environmental and biological factors come into play that makes no two high blood sugars the same.

The solution to putting some order to this chaos, and avoiding lows from stacking, is to reduce some portion of new insulin when there’s still some previous insulin hanging around. The IOB from one bolus becomes an IOU towards the next. It’s like making a down payment. There’s no need to pay the full balance on that new sofa if you’ve already paid for part of it, right? All you have to do is pay off the balance.

So what should you reduce? For routine operations, you should only reducethe correction portion. Why? Because you’ve done your level best (even though it’s doomed to failure) to properly count your carbs on the meal you are about to eat. You need to fully deliver the insulin required to cover that food, because if you reduce your meal bolus you guarantee that there’s not enough insulin to cover the meal—resulting in a high blood sugar down the road. On the other hand, any insulin not used up from previous operations, when added to a correction bolus, will likely lead to a low, hence the need for a reduction in the correction. Viewed in this light, the IOB is part and parcel of any correction bolus.

The only time I’d reduce meal insulin is when you know you’ve had an extreme carb counting error. You’d know this, for instance, if three hours after a meal your IOB is in excess of four units, your blood sugar is at 121 mg/dL, and you’re dropping like a frickin’ stone. In other words, when there is a gross excess of insulin relative to blood sugar and it’s been a while since you’ve eaten.

OK, that’s all good and fine, you say, but, how the heck do I keep track of my IOB in the first place? Most modern insulin pumps do it automatically, but there are at least two options for users of pens and syringes. The fist is the most excellent RapidCalc App, which I highly recommend, although apparently this long-existing product is temporarily on hold while the developers strive to satisfy the Apple Store’s new policies on “medicinal dosing” apps. Oh fer crying out loud, Apple…

And the second choice is to use the AccuChek Aviva Expert meter, a mixed blessing piece of technology if there ever was one, which we reviewed a little while back.

Mike, type 1 from Wisconsin, asks: So, how do you advise patients on fiber in their food and carb counting? I’m pushing to be lower carb and am turning to more fiber (and protein), but never really took fiber into consideration in my carb count calculations... Should I???

Wil@Ask D’Mine answers: So, for anyone who doesn’t know this: In theory, we should count not only carbs, but fiber as well. And we should subtract the fiber from the carb count. The reason for this is that fiber is included in the carbohydrate total on our nutrition facts labels, but the fiber is not actually digestible, so it doesn’t have impact on blood sugar.

That means in point of biological fact, that if a food had, say 30 carbs but 5 of them were fiber, you only need insulin for 25 carbs. If you took insulin for the full 30 carbs you’d go low. At least in that same perfect universe we were talking about above.

In reality, the difference between total carbs and “net carbs” in most American diets is so slight that it’s within the margin of error of our carb counting. In other words, it really doesn’t make a difference.

As I find that just trying to get my patients to count carbs at all, much less subtract fiber, is a real challenge, I don’t usually advise my patients to subtract the fiber. With two exceptions.

Every great once in a while, I get a patient who is a control enthusiast. These are people who probably need a hobby other than diabetes, but it’s their diabetes they’ve adopted, and by God they are going to get it perfect. Personally, I think trying to get diabetes perfect is likely to substantially increase your risk of suicide, but it’s my job to give people the information they need and want, so I don’t judge. People like this can probably benefit from subtracting the fiber, and have the time and inclination to do it.

The other exception is for someone like you, who is embarking on a lower carb diet. With a reduction in carbs, fiber can become a larger element of the equation. In addition to this, many low-carb foods are higher in fiber in the first place. So I think you definitely need to make this part of your equation. Just for fun, crunch your numbers on your next several meals both ways, and see what the difference in advised insulin is. I think you’ll be shocked.

Oh, and by the way, after a week or so of low-carb eating, you’ll probably find you need to reduce your basal rate. Most low-carb eaters don’t need as much insulin of any kind.

For what it’s worth, I know that there is endless argument over the “best” diets for diabetes. I don’t play favorites, but I can tell you that my people who eat low-carb have an easier time controlling their blood sugar. Both type 1s and type 2s use less insulin, have better A1Cs, and suffer less glycemic variability when eating low-carb.

But they are also more stressed out, less happy, and have an exceedingly difficult time eating out almost anywhere.

This is not a medical advice column. We are PWDs freely and openly sharing the wisdom of our collected experiences — our been-there-done-that knowledge from the trenches. But we are not MDs, RNs, NPs, PAs, CDEs, or partridges in pear trees. Bottom line: we are only a small part of your total prescription. You still need the professional advice, treatment, and care of a licensed medical professional.

Disclaimer: Content created by the Diabetes Mine team. For more details click here.

Disclaimer

This content is created for Diabetes Mine, a consumer health blog focused on the diabetes community. The content is not medically reviewed and doesn"t adhere to Healthline"s editorial guidelines. For more information about Healthline"s partnership with Diabetes Mine, please click here.

Type 2 Diabetes Treatment
Type 2 Diabetes Diet
Diabetes Destroyer Reviews
Original Article
#DiabetesMellitus