Ah yes, the great debate in the diabetes world; right next to, ‘what’s the difference between novolog and humalog’. When it comes to carbohydrates, are you supposed to bolus off of Total Carbs or Net Carbs? What are Net Carbs anyways? And why is the consensus so split?

What are Net Carbs?

Net carbs are total carbs minus fiber. For example, if your breakfast has 20g of total carbs and contains 5g of fiber, then the amount of net carbs would be 15g.

how to calculate net carbs

Some people bolus of net carbs and others bolus off of total carbs. But why would someone bolus off of Net Carbs instead of Total Carbs?

Why Would I Subtract Fiber?

Fiber is a type of carbohydrate that does not get digested by the small intestine (the place where food gets broken down and pushed into your bloodstream). And since the small intestine lacks the proper enzymes to break down fiber it therefore does not have any effect on blood sugar levels.

Fiber does not raise blood glucose levels because it is not broken down by the body, the fiber in an apple or a slice of whole grain bread has no effect on blood glucose levels because it isn’t digested. The grams of fiber can actually be subtracted from the total grams of carb you are eating if you are using carbohydrate counting for meal planning.

(Joslin Diabetes Center source)

Side note… If you’re wondering, ‘well then why the heck do I eat Fiber if my body can’t even digest it? I thought Fiber was good for you’. It is! It’s  great for you! It isn’t until fiber reaches the large intestine (a place where it has no effect on blood sugar) that it gets broken down and eaten by your good gut bacteria.

It’s for this reason that people bolus off of net carbs instead of total carbs; Net carbs are the amount of carbs that your body will break down come digestion time. Net carbs are the amount of carbs that affect your blood sugar levels.

How Do You Bolus for Carbs?

I’m curious, how do you bolus for carbs? And what has your experience been like?

Share with a T1D you love Earn good karma points. Share this with a T1D.

total carbs vs net carbs pinterest


  1. Rick Phillips July 10, 2018 at 8:38 pm - Reply

    I bolus off of total and ignore protein. i have been told that if you subtract fiber you have to add back protein. I am all about total,us totallers have a difficult time in in a net carb world. Grrrr. I hate these discussions.

  2. Megan Marquez July 14, 2018 at 9:50 am - Reply

    I use net carbs. I am like you the small amount of carbs will drop me as well.

  3. Ally Loore September 4, 2018 at 11:05 am - Reply

    I bolus off net carbs now too. Originally my nutritionist told me to only subtract fiber if its more than 5g and then only subtract half. It was too much math and didn’t make sense….and I would always drop. Sometimes a textbook doesn’t have all the answers – they don’t get that. Thank you for this article!

  4. Adrienne February 19, 2019 at 7:56 am - Reply

    Does it matter if it’s soluable or insoluable fiber?

  5. Jon February 20, 2019 at 1:13 pm - Reply

    I had been blousing off net carbs but I find I’m am going high all the time so I’m trying total carbs now. I figure I’ll end up in a swag somewhere in between.

Leave A Comment