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Diabetes Knowledge

Pro tip: master the pre-bolus to stop high blood sugars

4/8/2015 by Scott Johnson

Pro tip: master the pre-bolus to stop high blood sugars

Don't discount the power of the pre-bolus! My friend and colleague (and fellow Diet Coke aficionado) Ilka has some great tips to harnessing the magic of the pre-bolus, and reminds us that it’s still a very useful tool in our diabetes toolbox.

Ilka: Many of us have a real love/hate relationship with carbohydrates. They have the biggest impact on blood sugar and often drive us crazy trying trying to get it all right.

And it often seems that even when we do get it all right, our blood sugar is still not back to where it should be for our post-meal readings. Here’s where the pre-bolus trick comes into play. But in today’s times of modern, fast-acting insulins is it still a valid concept? Great question! Let’s talk about it...

High blood sugar after meals

It can be really frustrating when your blood sugar shoots to the moon after eating, especially when you can’t seem to figure out how to get back into your goal range soon after. As a general rule of thumb, you should be no higher than 180 mg/dl (~10 mmol/L) (according to the ADA). If it’s higher, you might want to look at a few of the usual suspects:

  • Is my insulin to carb ratio correct?
  • Did I count the carbs accurately?
  • Was there a correction bolus?
  • If so, are my correction factors right?
  • Is my basal rate set properly?

Once you feel good about these, then it’s time to take the wind out of the sails of those nasty post-meal spikes with some pre-bolus action.

The secret behind pre-bolus timing

What exactly is pre-bolusing?

A pre-bolus is taking your meal bolus “xx” minutes before eating to better match your insulin’s peak action time with your meal’s digestion. Why do I say “xx” minutes? Because it’s different for all of us, and even for each of us, it can be different depending on the situation and circumstances, which is what we'll talk about shortly.

For me, pre-bolusing is the ultimate solution, even if the pharma companies claim it’s no longer necessary. Remember back when we used Regular insulin and were supposed to inject 45-60 minutes before eating? Wow…

With the fast-acting insulins available today we have much more flexibility, and some insulins – Apidra, for example – are even approved for dosing up to 20 minutes after starting the meal!

But the lucky ones among you who have access to a CGM can see that despite these great new insulins, we still often experience a very significant post-meal spike (of course it depends on the type of food, too).

This spike can be nicely countered by simply changing when you take the insulin. Think of it as giving the insulin a "head start" in the race against the food digesting and raising your blood sugar.

How much time? How many minutes before eating? Everyone has to figure it out for themselves because insulin absorption and food digestion speeds are different for all of us. Puh! Wouldn't it be nice if the diabetes monster worked exactly the same for all of us?

If I start with an initial blood sugar in the green area, 15 minutes works great for me and I can usually avoid going above 150 mg/dl (~8.3 mmol/L) (of course this may vary with the type of food).

So how do you find your sweet spot (the right timing)?

Try to observe, and take it slow…

Test often and document everything. Blood sugar, type of food, amount of food, insulin to carb ratio, pre-bolus time, and anything else you can think of that might help. From this information you can draw wonderful insights.

Here are a few more pointers:

  • Rapid BG spike soon after eating → not enough time between pre-bolus and eating.
  • Rapid BG drop soon after eating → too much time between pre-bolus and eating, or maybe BG was already dropping.
  • BG rises first, then drops rapidly → not enough time between pre-bolus and eating and perhaps carbs calculated too high.
  • BG drops first, then spikes rapidly → too much time between pre-bolus and eating and perhaps carbs calculated too low.


The pre-bolus strategy isn't always realistic (snack attacks, for example), and it does require a lot of discipline.

Eating out is a little harder, too. At restaurants, I usually take a portion of my bolus when ordering and the rest once the food is on the table. I often order a glass of juice for the table, for safety against lows, just in case the food takes a looooong time to come.


The pre-bolus technique is a great way to keep those nasty post-meal spikes away. But it takes some trial and error to find the right amount of time that works for you (and don't forget, that time can be different for different meals and foods).

And don't be afraid to lean on your endocrinologist, diabetes specialist, or health care team for help. If you have gastroparesis (delayed stomach emptying), or hypo-unawareness, you should not try this before talking to your diabetes specialist about it.

Thank you, Ilka! Great information. The pre-bolus is something I've always agreed with logically, but struggle with in practice because it requires so much discipline and planning. In fact, I've written about my struggles with it before. Our friend Kerri has also written about it, and generated some great discussion in the comments. Well worth reading. 

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Scott Johnson

Almost famous for being a Diet Coke fanatic, Scott is the Patient Success Manager, North America for mySugr and has lived well with diabetes for over forty years. He's an active pioneer in the diabetes social media space and along with his work at mySugr, he manages his award-winning blog, when time allows.