Basal Insulin: What's the right amount?

The sad thing about doctors is that they aren't engineers, and this is doubly true for lawyers. So when you read about medications, everything's written by people who (a) don't think in terms of getting results out of feedback control systems, though that's what the body's all about, and (b) do think in terms of, "If I say something blatantly wrong, I'll get sued, but if I'm mealy-mouthed, I'm safe." This means that the dosage adjustment (titration) instructions for Karl's long-acting Lantus insulin are vague and simplistic, even by the standards of the intelligent layman: http://www.lantus.com/hcp/titration.aspx. Thanks, health-care industry!

So let's talk about feedback control systems, which is a fancy term for something that everyone already knows a lot about. If you set the cruise control on your car, the car will run at the speed you set, increasing the throttle when you're going uphill, decreasing it when you're going downhill, etc. Going up a really steep hill, you might not have enough horsepower to maintain your speed, so you slow down: "flat out" is all you've got. On a downslope, you might go faster than the speed you selected. So cruise control keeps everything constant under a certain range of conditions, but outside this range, you get what you get.

Karl's pancreas is still making some insulin. The pancreas has a very cool feedback control loop which, like cruise control, puts insulin into Karl's system at the right rate to keep his blood-sugar levels constant, within a certain range. The problem is that his pancreas can't make enough insulin to keep his blood sugar under control under most conditions. His pancreas' accelerator is pressed all the way to the floor and he's still not at cruising speed.

If we get his dosage right, injected insulin acts like a strong tailwind, allowing Karl to get up to speed without making his pancreas run flat-out. To continue the auto analogy, this reduces wear and allows it to cool off, so it will last longer.

Not only that, but by allowing the engine run most of the time at, say, 50% power instead of 100% power, if we get an unexpected hill, we can get over some hills without slowing down, because we have reserve capacity. Turning the analogy back to diabetes, if Karl eats a larger portion than we had calculated, so he receives less insulin than he should, or sneaks a snack without any insulin at all, his body has reserves that will cover it without spiking his blood sugar. Sweet!

Because Karl's pancreas is producing some insulin on its own, he can receive different doses of long-acting insulin and arrive at the same average blood-sugar levels. If he gets a low-ish does, his pancreas will provide more insulin, and if he gets a high-ish does, it will provide less. So within this range, the results will be equivalent -- except to his pancreas!

Since the goal is to keep his pancreas from being overloaded, we're aiming for a dose on the high side of this range. So far, we've determined that a dose of Lantus anywhere between 6 and 8 units per day gives about the same results, and we'll probably test 9 units soon. We're adjusting no more often than once a week, since day-to-day variations are wide enough to obscure the results.

Precision: Matching Carbs to Insulin

How can we get more precise control over blood sugar? We've been experimenting with a way that seems obvious but I haven't seen mentioned anywhere: Match the carbs precisely to the insulin dose.

For example, suppose Karl is going to sit down to a lunch of 51 carbs, for which, at 15 carbs per unit of insulin, he's supposed to get 3.4 units of insulin. Well, we can't give him 3.4 units. We can give him 3.0 or 3.5, but not 3.4. 

Because giving too much insulin is worse than giving too little (since giving too much leads to low blood sugar and the troubles that it causes, from hunger to fuzzy-mindedness to loss of consciousness), we round down, and Karl would get 3.0 units, which is four-tenths of a unit short of what he needs. We'd expect his blood sugar to end up about 40 points too high because of this.

On the other hand, if he had 52.5 grams of carbs, that would work out to exactly 3.5 units, so we could be right on the money. All we need to do is find 1.5 grams of carbs in a Karl-friendly package. What we use are Ritz Bitz, which come out to about 1.5 grams each. Problem solved!

So now he's getting anywhere between zero and four Ritz Bitz with every meal. It seems to make a real difference when his carbs are just short of the next insulin increment.

If you're using an insulin pen but aren't using one that allows half-unit dosage, you should be! The NovoPen Junior has been working very well for us. If we had to give insulin in one-unit increments, the number of Ritz Bitz we'd give Karl per meal would go as high as nine! He'd like that, but we wouldn't.

Routine Doctor's Visit

Since there isn't a doctor who specializes in diabetes in our area (an endocrinologist), we're seeing our GP, Shawn Foley, for Karl's checkups. We got a thumbs-up, as we knew we would, and Karl had gained a couple of pounds since last time, which is good, since the bout of diabetic ketoacidosis that resulted in his being hospitalized and diagnosed left him thin. And we got a prescription for more test strips per month, since 200 test strips is only 6.7 per day, and we often go above that. (Especially because the school is very good about testing his blood-sugar levels before and after P.E. to ensure that he doesn't exercise his way to low blood sugar and its attendant problems.)

Is Karl's "honeymoon period" lasting? That's the big question. At the hospital, the doctors claimed that his pancreas' ability to produce insulin was a write-off, and it would vanish soon, in a matter of weeks or months (it's been four months now). This would reveal itself through degraded blood-glucose control and increased insulin requirements. Before this week's doctor's visit, I printed out the trend graphs from Karl's Bayer Contour USB blood-glucose meter, and noticed that his blood-sugar was under slightly better control during the most recent 30 days than it was during the previous 30 days, and his insulin requirements are about the same. That's good!

He might have been doing a little better before that, but it's a little unclear because we didn't start taking after-meal blood-sugar readings in the early weeks, so this revealing piece of the puzzle is largely missing. On the whole, it looks like he's holding steady.

This is good, because, for example, if he comes home from school with a blood sugar of 140, it will be down to a more normal 80-90 by dinnertime without corrective insulin. While we want to keep the load on his pancreas down to a minimum, we're glad it's there to fill in the gaps!

We have been adjusting Karl's insulin dosage on our own, which seems to be standard practice these days. The first several times we did it, we bounced it off someone on our diabetes support team, but since they always agreed with us, we kinda stopped. It's always a matter of tweaking doses up or down by half a unit and keeping a watchful eye on happens, and Karl eats the same meals over and over, so this is not rocket science! What works and what doesn't is revealed quickly.