Tweaking an Extended Bolus

Extended Bolus: making adjustments for better results

If you’ve ever tried to use your Insulin Pump’s Extended Bolus Feature (Combo Bolus, Square/Dual Wave Bolus) and it was a flop... we can help you figure out what went wrong. And how to fix it! Find out where to start when using an extended bolus, how to adjust the settings based on the blood sugar results that follow, and what to do if an extended bolus isn’t enough.



  • There’s an initial drop in blood glucose followed by later high blood glucose, and
  • The meal was low GI, high protein, and/or high fat, and
  • The basal rates, I:C ratios, and carb content have all been confirmed as accurate


  • An Extended Bolus may be helpful for smoothing out the post-meal valleys and peaks.

If That Is the Case

We suggested that you experiment with the Extended (Dual/Square-Wave/Combo/Multi-wave Bolus) feature of your child’s insulin pump: try an initial combo bolus, monitor blood glucose closely (wise whenever you mix up the management routine!) by checking and recording the blood glucose results at 1-hour post-meal and a few times (1-2 hours apart) in the hours following the meal. This will give you the data needed to determine the effect of the Extended Bolus.

But where should you start? And what should you do with the results?

Where to Start with an Extended Bolus

An appropriate split of the Normal and Extended portions of the Extended Bolus depends upon a number of factors, including:

  • The GI of each of the foods eaten
  • The combination of foods eaten (Is your child eating a large proportion of low-GI foods? Mostly moderate-GI foods? Mostly a high-GI food with some small amount of low-GI food on the side? Each of these situations would benefit from a different insulin split.)
  • The fat and protein content of the meal,
  • Individual differences

We suggest that you wade into the (dual) wave with a conservative starting point, and carefully analyze the results:

Tips from the Trenches

There is no magical starting point for experimenting with a combo bolus; the numbers will be different for each individual. So we can’t tell you exactly how to do it, but we can tell you our story…

When we’re trying out a new food that we think needs to be combo’d, we often start with a 50/50 split over 3 hours. That is, 50% of the meal bolus will be delivered up front, with the remaining 50% being infused slowly over the following 3 hours. The BG response gives clues as to how we might do things differently next time (or not). ~Danielle

How to Adjust the Split Based on the Results

If your child just ate pasta using an Extended (Combo) Bolus for the first time, and the resulting blood glucose flat-lined at 6.0 mmol/L for the following 12 hours, then congratulations! Your experiment is done.

But for the other 99.9% of us, a bit of post-experimental data analysis would be helpful. Here are some things to consider:

If blood glucose drops early in the meal despite the use of an Extended Bolus, this may indicate that too much insulin is still being delivered up front: try a smaller number for the 1st part of the ratio. For example, if your initial split was 50/50, you could try 40/60, or even 30/70.

Conversely, if blood glucose rises significantly early after the meal, this could mean that not enough insulin is being delivered upfront: try a larger number for the 1st part of the ratio. For example, if your initial split was 50/50, you could try 60/40, or even 70/30.

If blood glucose is steady for the first few hours around the mealtime, but rises suddenly a few hours after the meal, this may indicate that the insulin “tail” is too short: try spreading the extended portion of the bolus over a longer time period. For example, if initially, you used a 50/50 combo over 3 hours, you could try extending the same split over 4 hours.

Tips from the Trenches

I keep a notebook in the kitchen with a page for each common “problem meal”, like spaghetti and meatballs, rice and beans, or rice noodles with stir fry. (The list of “problem meals” is finite, and relatively short for us.) When my son eats a certain meal, I make note of the split and the time period we used, and then record the BG results over the next several hours until the combo has expired and all the insulin has been delivered. Looking at the BG results, I then decide whether that combo configuration worked or not, and whether the results were bang on, close, or an epic fail. Then I analyze the results as outlined above AND write down a suggestion too myself for what to do next time. After a few meals of a given type, I can look back at the collection of results to see patterns and adjust my approach. ~Michelle

Extended Bolus Not Enough to Manage Post-Meal Spikes?

For meals with a high fat content, you may find that, in addition to using a Combo Bolus to address slower digestion, it may be helpful to set a temporary basal rate increase to address the insulin resistance that comes from fat intake. In these cases, check out the Double Whammy Approach in’s Adjusting Choose the Right Glycemic Index for the Job article.

The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.