Using the Extended Bolus Feature in Real Life

Picture this: It’s Friday night. You’re at a restaurant for dinner with a bunch of your friends. You’re craving something delicious after a hard week.

You decide to go fancy and order some surf and turf with vegetables and cheesy cauliflower mash. The group orders some oysters to share. Your mouth is watering.

Low carb, right? Your starting blood glucose is 104 mg/dL. 1 unit of insulin is taken for the veggies.

You go to bed at 11:30 PM with a blood glucose of 135 mg/dL. Nothing to worry about, right?

You wake up at 4:00 AM and your blood glucose is 265 mg/dL for no good reason. What went wrong?

Enter: Bolusing for high-fat meals.

How Fat (and Protein) Affects Blood glucose
I won’t nerd out and go all biochemistry on you, but for simplicity, fat has no real impact on blood glucose levels in isolation. 

What it does do, however, is delay gastric emptying, aka slows digestion. This can occur over a period of HOURS.

Why this matters: You are likely NOT consuming fat in isolation (if you are, more power to you). Instead, in this scenario, you are consuming it concurrently with protein.

**We interrupt this section for a quick word on protein.**

When consumed with carbohydrate, protein can augment the way the carbohydrate affects your blood glucose, though minimally. Unless you consume an excess amount of protein, you likely won’t notice much of an effect at all. When protein is consumed in the ABSENCE of carbohydrate, however, it will break down the excess into glucose during a process called gluconeogenesis.

On average, each excess gram of protein will break down into roughly 0.6 grams of glucose.1  

Now, imagine the meal above. If you are eating 50-plus grams of protein, that potentially has the effect of 30 grams of carbohydrates on your blood glucose.  

**Back to your regularly scheduled program.**

The effect of the glucose from the protein won’t be seen immediately. It may take an hour or two to even notice any increase in blood glucose. Now, add fat to the equation, which will slow the increase in blood glucose even more. Then a CGM graph will reveal a steady increase in blood glucose levels over a period of many hours.

Let’s set this scene up again:

  • high fat, high protein, low carb meal
  • if we assume 50 grams of protein, it could impact blood glucoses similarly to about 30 grams of carbs
  • fat slows digestion, so the ~30 grams of carbs aren’t even seen in total until hours later

How Do We Solve This? 

There are two real options to consider, one of which is more sensible: 

  1. Set an increased basal rate for two to eight hours after the meal
  2. Set an extended bolus to cover the meal for two to eight hours…

 **Disclaimer: The two- to eight-hour range is NOT a range set in stone – you will need to experiment with what works for you and what does not.**

While the first is simpler, it is not optimal because:

  1. Basal rates fluctuate through the day and night, so the amount of insulin to be increased is not consistent
  2. There is a max rate of basal one can receive per hour, and your needs for the meal may exceed this rate.

Thus, let’s talk extended boluses!

What is an extended bolus?

The t:slim X2 Insulin Pump’s extended bolus feature allows the user to take an amount or dose of bolus insulin over a longer duration of time. Humalog and Novolog peak quickly (between 30 min to 3 hours), and last approximately two to five hours. The effect on lowering blood glucose may be out of the body too early to help avoid this delayed increase in blood glucose. Additionally, their peak may be too soon and lead to hypoglycemia...BEFORE the effect of the high fat meal kicks in!

However, with an extended bolus, pump users can take some insulin up front and then have the rest administered at a consistent rate over whatever time period they choose. For example, one could take 20% up front and then 80% over four hours.

Ideally, this strategy can be used to combat the delayed blood glucose increase by allowing users to have a higher amount of insulin active when their blood glucose starts to rise, and ideally blunts that possible spike or prevents it from even happening.

Read more about extending meal coverage with the Extended Bolus feature.

For more information, please visit

What Percentages Do I Need to Use? 

This, my friends, is the beauty of diabetes: There is no “one size fits all.” There is no right answer. What works for me may not work for you and vice versa.

There are, however, some tips for success you may want to consider:

  1. Track, log, or journal about how each attempt goes! It takes work, but it may help you get closer to the ideal up-front percentages, extended percentages, and ideal time frames that work for you.
  2. Alter ONE variable at a time! If you change more than one variable at once, such as time frame and percentages, and it works, you won’t be sure which variable caused the success. Changing one variable at a time takes longer, but it can help you better identify what works and doesn’t work for you.
  3. If something doesn’t work as expected once, don’t give up. We all know about diabetes, what works one day may not work the next – despite everything being same – so try not to get discouraged. Think of it as a learning experience.
    1. Note: If your strategy repeatedly doesn’t get you the results you need, then it may be time to try something else.

Bonus Question: What if I Ate Carbs with a High Fat Meal? Does that Change Anything?

Answer: Yes and no. The carbs will raise your blood glucose as anticipated, but the fat may prevent your blood glucose from dropping as easily.

Why? The delay in gastric emptying is almost like a consistent flow of glucose being released in the blood over many hours. OR, you could choose to see it as the fat making one more insulin resistant.

Either way, the end result is the same: elevated blood glucose levels for many hours, requiring more insulin than usual to bring it down.

Author Bio: Ben Tzeel has lived with type 1 diabetes since 1999. He has a master’s degree in nutrition from the University of North Carolina at Chapel Hill and is a registered dietitian. He is a Certified Strength and Conditioning Specialist (CSCS) through the National Strength and Conditioning Association, is a published fitness model, and writes about exercise and nutrition. 

Ben Tzeel was compensated by Tandem Diabetes Care for his contribution on this topic. However, he created the content and it is based on his personal knowledge, experiences, and observations.

1Oexmann MJ. T.A.G.: A Diabetic Food System. New York, NY: William Morrow & Co.; 1989.

If you’ve never used the extended bolus feature before, talk to your healthcare provider about strategies for using it to make this holiday season a little easier to manage. This information is a summary only, if you’d like to learn more please reference your pump’s User Guide for further information.

From time to time, we may pass along: suggestions, tips, or information about other Tandem Insulin Pump user experiences or approaches to the management of diabetes. However, please note individual symptoms, situations, circumstances and results may vary. Please consult your physician or qualified health care provider regarding your condition and appropriate medical treatment. Please read the Important Safety Information linked below before using a Tandem Diabetes Care product.


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