Ever indulged in a little pizza with the kids or Italian food on date night, gone to bed at a perfectly respectable blood sugar, but then woken up in the middle of the night with a sky-high number that has you racing for the bathroom?

If you have, then you've encountered a dreaded delayed postprandial spike, which happens when food takes longer than insulin to enter your system. Usually it's the other way around. Fast-acting insulin starts working in 10-15 minutes, peaks at 1 to 2 hours, and then slowly tapers out. It's usually out of your system after 4 to 5 hours. But in a few special cases, the insulin finishes working long before the bulk of your food ever hits your system.

Typically this happens with high-carb meals that are also high in fat, like pizza, Chinese food, Mexican food, etc., because the fat delays the impact of all those carbs on your blood sugar.  Sometimes even super high-carb meals, like some Italian dishes, which have a lot of carbs but is low on the glycemic index, and perhaps not as much fat, can still take hours to digest. According to endocrinologist Dr. Lauren Golden, that's because "the food essentially sits in a ball in your stomach. The more carbs you have, the longer it takes to digest." Dr. Golden and her team at the Naomi Berrie Diabetes Center recommend using a so-called "dual wave bolus" for any meal with carbs over 70 grams.

Ever heard of the dual wave? Medtronic has actually trademarked that term...

The deal is that most modern insulin pumps now have an option for changing how a bolus is delivered to deal with this latent effect. They allow you to set a certain percentage of your total meal bolus to be given immediately, with the rest to be slowly delivered over a period of time. In Medtronic pumps, it's called a dual wave bolus, and as noted, that company has cornered the market on that terminology.  So in Animas and Cozmo pumps, it's called a combo bolus, and in the OmniPod, it's called an extended bolus.

Despite best intentions, using this setting is tricky. Personally, I shamelessly use a regular meal bolus for everything under the sun. But I almost always suffer the consequences with a middle-of-the-night run to the bathroom when a sudden surge of carbs hits my system that my insulin is no longer prepared to handle. This is often after sliding into bed with a low or almost-low blood sugar because of too much upfront insulin.

Want to brush up on this technique?  Warning: it can be very tricky to know exactly how long some food will take to absorb, so this is likely going to take quite a bit of practice. Different high-fat, high-carb meals will affect you differently. First recommendation is to try it while using a continuous glucose monitor (CGM), even if only temporarily, so that you can literally see what's happening with your BG in real-time. Many clinics now have CGMs that patients  can check out as loaners for a week, so you can test out how you react to certain foods.

Kelley Champ Crumpler, a diabetes nurse educator and type 1 herself, shares this tidbit: "At the ADA Scientific Sessions in 2009, I attended a talk discussing CGM, and some slides were shown on extended bolusing. Of the T1s wearing CGM that ate pizza, many were still absorbing the carbs (hence experiencing the glucose rising) after 8 HOURS!! What the frappuccino?! This was VERY eye-opening. So for pizza, I have patients extend their bolus for at least 6 hours to prevent this!"

What the frappuccino is right!

If you're just starting to explore this advanced pumping technique, give the 60/40 rule a try. Upfront, set your pump to deliver 60% of your bolus at the meal, with the remaining 40% being delivered over the next four hours. Some people might find that too little, so you can also try out 70/30 or 80/20, depending on how what you're eating. But don't just ride it out — you have to fine-tune with lots of testing. Kelley recommends checking every 30-60 minutes when testing the split-bolus method.

"An excursion of 30-50 mg/dL is acceptable," Kelley says, "But a rise of greater than 2 mg/dL per minute is too fast, and I would consider more insulin."

Another advanced pumping tool I've been looking into is the square wave or extended bolus (again, the name depends on your pump company). Less common than the dual wave, it's a constant drip of your bolus insulin over a period of time, with no upfront insulin given. Since at least some food hits the system right away, this doesn't work for a lot of scenarios. However, holiday parties (which are just around the corner — November is next week, ya know!) are a perfect opportunity to employ this tactic.

"The square wave bolus is good for a cocktail party, grazing, or if you will be eating a constant amount of food over a period of time, like popcorn for 1+ hours at a movie," says Caroline Bohl, CDE and registered dietician at the Naomi Berrie Diabetes Center.

Of course, just because you're not on an insulin pump doesn't necessarily mean you're not still facing this problem. If you're using multiple daily injections with Lantus or Levemir, you can still partake in extending your insulin action. Gary Scheiner, type 1 PWD and famous CDE at Integrated Diabetes Services, recommends using one of the following options:

  1. Take the meal dose after eating
  2. Split the meal dose into two parts: half before eating, half after eating
  3. Take Regular (R) instead of a rapid analog insulin

Mastering the dual wave bolus looks like it could be aggravating... Good thing there are many ways to handle heavy carb/fat-laden meals, with the dual wave being just one of them. Some folks use a temporary basal rate to handle sneaky spikes. Personally, I'm not sure a four-hour dual wave does much for pizza. Then there are times where I seem to spike no matter how much insulin I give or how much I extend!

But Kelley has some words of wisdom: "Diabetes is like a fingerprint, so different for all of us. What works for me won't work for you, or for my hubby [also a PWD]. A lot of advanced pumping is trial and error, so if it doesn't work the first time, don't get frustrated.  Just make adjustments the next time! You are in an even better position if you have, and wear, a CGM, as you will know immediately if something isn't working."

Although pizza and Mexican food are not on my regular menu, they are foods I enjoy and don't want to give up permanently — but sure as heck don't want to suffer the late-night wake-up calls either! Assuming you indulge every once in awhile, how do you handle the ramifications from high-carb meals? Are you pro-active with your bolus settings or do you just "ride the highs"?


