How do you carb count?


I’ve heard different opinions on counting carbs. Specifcally, how do you factor in fiber.

I have a T1D relative who says he subtracts ALL the fiber from total carbs. I aslo read a book saying the same.

However, a dietician certified in diabetes (whatever you call them) told me to only subtract fiber if it’s more than 4 gr, and you should only subtract half of the fiber (e.g., 5 grams of fiber you subtract 2.5 from total carbs). I’ve heard some don’t subtract fiber at all, and some even dive real deep into sugar alcohols and more.

Curious about what everyone does/the philosophy they follow. Thanks!

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@JakeVA ,

CDEs, CEDES, or whatever they are called now are a closed shop group like faces. We all have one and they are all different. I was taught 20+ years ago by 3 CDEs, endo’s CDE nurse pump trainer, Animas CDE nurse pump trainer, & Dexcom’s CDE nurse pump trainer. The three nurses assured when I counted carbs, every carb was counted. I asked about fiber & sugar alcohols. The three taught if it a carb, count it as a carb.

I use three carb indexes for foods, CalorieKing, MyFitnessPal, and the food or restaurant web. What ever the carbs is what I put in my pump. Has worked so far very well and I don’t need to do funky math counting this, excluding that. I recently saw a dietician with a different specialty. She was preaching “net carbs”. In all my years of training & retraining every time I changed pumps, I learned one thing. If a dietician starts with anything about “net carbs”, they are preaching snake oil and are forever lost.

Hope this helps.


Like @987jaj I was taught that “a carb if a carb” and I’ve never subtracted out fiber. What are you doing, and how is it working for you?
If I were going to experiment (and I’m not) I would first see how it works without subtracting any, then try the other extreme of subtracting all; and if that yielded vastly different results and neither got me where I wanted, then I would try the formula and see how it works (but first my question for the nutritionist would be where did you get that formula?)
To make the experiment as accurate as possible I would have to eat the same meals for a few days with each method and try to keep other variables such as exercise and stress, the same.

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Dorie, my training & retraining has need wonderful using “a carb is a carb is a carb” with none of the net carb malarkey.

When I would visit a Cracker Barrel Old Country Store to eat & ask for a nutrition guide, I would be given a menu list with only net carbs.


I should have added that the dietician said the research is mixed on carb counting for fiber and IF you deduct fiber, only do half of the fiber over 4 grs. She also loathes the marketing term “net carb.” It’s for Keto (which is another can of controversial worms).

I haven’t really seen a difference either way. I know certain foods don’t spike me, but those are usually non-starchy veggies and nuts/peanut butter.

Bread or granola bars or cereals with high fiber over 4gr still raise me all the same. So I think it’s all personal or at least your matching your ratio consistently whether you deduct or not. I don’t pay much attention to them at this point, I just do total carbs and exclude certain foods from my total.

Hi @JakeVA I don’t think there is a “right” answer here I think you should do what works for you. If you eat consistent fiber and you wanna subtract all of them then you will end up with a carb ratio that makes it possible. If you do something different you will end up with a carb ratio that makes it possible. I generally use “grams carb” and modify for fats (more fats need more insulin over a longer time) and activity (more activity needs much less insulin). So while I don’t know the right answer, I do know what works for me. Good luck :four_leaf_clover:

Mostly you’re only dealing with a few grams of fiber so you could try subtracting them and if the sugar runs higher than expected put them back the next time and see how that goes…

I’m confused as to why this is snake oil/malarky - any enlightenment would be helpful. My understanding is that fiber is not digested. If it is not digested, glucose is not extracted. If glucose is not extracted, it cannot affect blood sugar. ?

@BKN480, although the carbohydrates are not truly metabolized, there is enough entry of the fiber into the digestive process to create glucose alteration in insulin demand.

For example, if I eat an Abbott Zone Perfect Bar with zero fiber & 24 grams of carbs, dosing accordingly, I come out fine. On the flip side, if I eat soup beans & subtract the fiber, my insulin dose is insufficient to prevent a return to a pre meal level 3-5 hours later. The lack of return means the fiber entered my metabolic pathway somewhere, somehow.

My training team members over the years have shared my example is seen frequently enough to teach ‘net carbs’ need inclusion in the insulin dosage calculations. The training team over the past 20+ years has included 6 RN pump training CEDES. (CDEs) representing my endo, Animas, Dexcom, & Tandem.

The consensus of my team was if someone leads in with ‘net carbs’ watch out for the snake oil carnival barker.

I will also send you a message.

Thank you for your reply, I appreciate it. Always continuing to learn, and will consider this more w/ respect to my own experience (not that I haven’t felt like I’ve been trying with a lot of exhausting effort and detailed attention already to figure out what the heck goes on w/ my body and insulin and glucose…! but more info and others’ experiences is always helpful and again, thank you!)


Becky, there is one more called SWAG. Read on.

Years ago, before Tandem’s BIQ & CIQ, when I was on a basic pump and an earlier Dexcom 7sts, I ate supper out three evenings in a row. Same place, same food, after work conference. Calculated carbs entered into pump the same dose when food placed on table and ended up with 3 different outcomes. One high, 1 low, and 1 on target were the results 2-3 hours after the meal.
My wife and I were majorly befuddled and asked our endo’s nurse CDE pump trainer what happened. With restaurants doing portion control, etc, the carbs should have been the same, right? The CDE responded the situation was a SWAG. My wife & I gave her a quizzical look to which she responded, “Scientific Wise Ass Guess”. She further explained there is not explanation.
I hope this helps you see you can do everything right and things will still go haywire.

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That’s a great anecdote, thanks. SWAG - was skeptical of this term (a fancy acronym for what dubious “medical” analysis?..) but pleasantly surprised to find out what was meant by it. Yep indeed, SWAG is entirely my experience w/ T1D, having had it almost two years now (not long I know, but long enough you’d think being attentive and observant would count for more than it’s seemed to) and keeping tabs on every single carb, insulin dose, glucose level, and other potential factors. It’s like my body just likes laughing in my face: “Oh you think this is how x and so-and-so works, well, let’s just straighten you out about that…” !

That’s the kind of question I expect from people who have recently changed to a new “protocol” -exercise, diet and behavior and aren’t sure what to do. Never be afraid to ask questions, to question the answers, because no one knows everything about anything.

What to do with fiber depends on whether you are a termite, a cow or a human, so you are better off asking this of a vet than an “medical doctor” or a “nutritionist”.

Unless you consider wood chips and hay as food, you should subtract dietary all fiber from your carb counts. Fiber is either soluble or insoluble in the human gut, but it is always indigestible.
If anybody tells you otherwise, they believe; they do not know.

They do not understand digestion or how to interpret the nonsense on food labels. Fiber is only under carbohydrates because it is not lipid or protein. Fiber should be shown as an inactive ingredient, as is done for medicine and supplements.

If fiber is listed as included under “Total carbs”, subtract all if it. It has no nutritional value for humans.

I don’t care what philosophy a doctor or nutritionist believes in. Those are “medical opinions”, not facts, but based on anecdotes and faith, like a religion.

I make decisions that effect my health based on facts and knowledge. As a human with type 1, if I didn’t subtract fiber from net carbs,no matter what I used as a insulin to carb ratio, I might as well be guessing.

btw, If you don’t look at added sugars as a percentage of the carbs in a meal, the response you get during the first two hours after you eat will be a surprise. If you don’t include enough or include too little fiber, your bathroom visits will too.

If you work to keep your diabetes well managed long enough you will find ways to simplify decisions because its too much work otherwise. You will eat more predictable meals of predictable sizes that include what you like to eat and nothing you don’t. You will condition your gut to expect certain size meals at certain times. That "diet will gradually change and you will become skilled at finding substitutes, one change at a time. You will look at new food and compare them to ones you know. Estimating food content will either become instinctive, or you will have a short list that you can refer to, not an encyclopedia of foods.

I have 4 breakfasts, 4 lunches and 6 dinner that I eat +45 weeks a year. My food diary has meal numbers, each meal has approximately 40 net carbs. I can substitute an ingredient for one of the fixed ones ad have a pretty close estimate of the effect,

If you are forced to eat food whose composition is unknown to you, the best you can do is compare it to things you know and compensate afterwards. When I eat out on vacation I mostly order things I know, with the variations being in fat and protein.

Thanks for reply. Questions for you (no judging just helping me collect data to aid in my decision):

  1. How long have you been T1D?
  2. Did you try the ‘total carb’ vs ‘net/subtracted fiber’ for a while (so you’ve experienced both)?
  3. Did you do any logs to compare a total vs ‘net’ approach? Assuming if you did, you saw a trend and it influenced your switch?

Also, can you share more about the added sugar comment? I realize this can make it a higher GI food, is that what you were hinting at?


What I’m finding is, that people who are long-time T1D and Doctors/nurses who are T1D, seem to deduct all fiber from carbs when carb counting. My T1D friend who was diagnosed later in life goes off what his endo tells him to ‘count all carbs’ including fiber. Same with nondiabetic health providers, they seem to suggest counting all carbs or doing some sort of half subtraction.

I’m trying two weeks with ‘net carbs’ counting and seeing if my post meal difference shows any trends compared to the post meal counting all carbs. I’ll repost in a two weeks what I learn.

  1. 45 years
  2. yes
  3. I’ve maintained meal logs for +30 years.
    If you are getting the same amount of fiber, consistently, your pump’s “auto” parameters may need to be changed. Your insulin to carb ratio will have been off.

I switched to carb counting from the ADA exchange system after 15 years when A1C tests became mainstream and showed that my lab BG tests were misleading.
My diet was high fiber. After I started subtracting fiber, my other numbers immediately became consistent enough that I was able tune my insulin to carb ratio and my carb to BG ratios and get my A1Cs under 6.

Most people in the US get too little fiber. Laxative companies love those people’s constipation. If you inadvertently are on a low fiber, subtracting it won’t make much of a difference to your control because your irregular digestion will make your our by hour reaction to foods unpredictable. The delayed conversion of fat and protein will put everything out of whack.

IMO That’s why the first thing a person with diabetes should do is make their overall diet healthy and balanced - including getting the correct proportion of fiber.

I believe that those two things are more important than the total amount of carbs or food you eat in a day or how “organic”, “vegan” or any other fad your diet is. You can always cover carbs with insulin if you get predictable results, but you can’t be predictable if your digestion isn’t. That’s why its hard to maintain control when you are ill, especially after taking oral antibiotics. ).

If you aren’t regular in your BMs, if the stools don’t look right, if you have gas, cramps, runs or constipation, no matter how carefully to measure your carbs and insulin, your BGs will be all over the place.

Thanks for sharing. I agree on a healthy diet is king. I eat really well (didn’t have to adapt much after being diagnosed), and I get more than enough fiber on a daily basis for the most part. The bit on digestion makes sense as that is where it all is absorbed.

What led me to consider subtracting fiber was I’d have some carb meal ratios figured out, but then one meal it was completely off and I dropped low quick. I noticed it happened whenever I ate beans. Beans have a lot of fiber and I was dosing for all carb.

For a two week test to be statistically valid, you’d need to be able to avoid making any corrections and “go by the numbers” no matter how far off your BG varied from target. You also need to be stable and fairly well managed. If corrections are consistently more than 10% of your daily carbs and insulin, imo, you aren’t.

I wouldn’t make any kind of diet change unless I was willing to make day by day adjustments to my assumptions. I would not rely on my current ICR or correction factor as being reliable.
If the difference was large enough to be worth the effort, blindly using old management parameters could be dangerous.

Finally, if you don’t have good data relevant data for your current protocol, you can’t compare it to the new. You need a way to calculate and compare meaningful error levels of the old new protocols. Insulin variability is the best control metric I know, but requires a CGM. If your A1c is stable, then correction percentages and fasting/bedtime BG differences are almost as good.

If it were me, before I made a potentially big change, I’d log all the carbs and all the insulin I took for two weeks. I’d separate meals and snacks from corrections. log my waking and bedtime BGs, not just mealtime values. Then I’d calculate my average total daily dose, my actual insulin to carb ratio, and regard the correction insulin and added glucose as strong indicators of where my protocol was weakest.

If my overall ICR was unchanged from the last time it was calculated, then I need to shift correction carbs to planned ones and possibly change insulin timing. If it has changed, then I need to adjust my doses and/or or my diet. olus"

btw, The fixed numbers that are casually given for insulin timing aren’t reliable. I change mine based on the fat and protein content of a meal. Pizza needs a bigger lead time than the same amount of carbs in a soup and sandwich or spaghetti. A pizza spike takes longer to come back down, but should- if the total B&b is correct.

@JakeVA Here are the answers:

When dx’d T2 10 years ago, the CDE training I received (3 different people taught the course) all said if fiber is over 5g, you can subtract it; if protein is over 5g, you can subtract 1/2 of it…they called it NET Carb back then. I was dx’d T1 1 1/2 years ago based on GAD and c-peptide, I asked the Endo if NET Carbs were the way to still count; my Endo said “If it’s carb, count it, period! Net carbs are an industry invention to sell their products.” My own research confirmed that; there’s no common formula, no government, FDA, ADA, or other standards setting convention. Just corporate greed trying to sell products to the “health” conscious public.

I’m no doc and not a food scientist, so my opinion is worth what you’re paying. However my understanding/research indicates fiber counts as a carb on nutrition labels and should be counted, Further, there is some controversy about whether the body can digest or convert part of the fiber and that fiber impact the speed, but not the fact of, other carb absorption/digestion.

All that said, each of us responds a bit differently. I know if I don’t count all the carbs, per the labels, my dosing will be off and my BG’s will be high…but intellectually, that might be affected by changing my ISF and ICR. Too many moving factors for me to decide. So I listen to the doc I pay for advice, balance it with my own research and experience and press on…