Taking Insulin for Protein, Fat, and Carbs

It has only been a little over a year ago that I realized my entire “Diabetes Schooling” was a lie. Here’s what I mean, when I was diagnosed eleven years ago, and even when I first saw an Endocrinologist five years ago, I was never taught the concept of taking insulin for fat or protein. I was always told that I need insulin just for carbohydrates. Now I know that all three macronutrients need to be figured when taking insulin: fat, protein, and carbohydrates.

Let’s get a few things straight:

  • Carbohydrates are not the only macronutrient to consider when injecting insulin, amino acids also break down and impact blood sugar (at a much slower rate than carbs) and lipids delay spikes.
  • Fat cannot be converted to glucose, but it will delay the spike from carbohydrates.
    • Think Pizza. This is typically why there’s a late spike, and a long breakdown into blood sugar that can have an impact 3-5+ hours after eating.
  • When eating carbohydrates, pairing fat and/or protein will nearly always delay the spike from carbs.
  • Protein breaks down in the body eventually, and inefficiently, as glucose, and will usually impact blood sugar around hour 2-5 after eating.
  • Not all Sugar Alcohols are created equal. Do your research and know which cause blood sugar spikes and those that do not. The label will not identify this as even sugar alcohols that break down into glucose are allowed to be subtracted from total carbohydrate count. Only the ingredient list will be helpful in determining if the net carbs are truly “net carbs”.

macronutrient breakdown

The above points are absolutely critical when it comes to injecting insulin. Let’s take a couple of real-world examples and put the theories to test.

Carbohydrates: I need to count EVERY carbohydrate when injecting insulin. It doesn’t matter what form it comes in, it will eventually break down into glucose and raise blood sugar. For a long time I used to wonder why my blood sugar would spike after eating a salad. Little did I know, even a head of lettuce has carbs and needs to be covered with insulin!

Protein: let’s say I eat this delicious Fulfil bar. It has 10g carbs (2g of sugar, 7g of sugar alcohols), 9g fat, and 20g protein per bar. Because the Fulfil bars are mostly made with sugar alcohols that DO NOT impact blood sugar, I count half the amount of carbs, so 5g carbs (I’ve discovered this through trial and error). In addition, I typically account for 60% of protein to eventually be broken down into glucose, very slowly. This is not based on scientific evidence, this is my experience. So for this bar, I would inject insulin for the 5g carbs, and 12g protein (.6x20g). Total insulin is calculated based on 17g, but the majority would be used as an “extended bolus”, so that I receive the 5g ratio upfront, and the 12g ratio over 30 minutes – one hour. The extended insulin will ensure that the protein spike is covered, even though it occurs hours after eating. Regular insulin, Novolin R, is also a great option for covering high protein meals.

Fat: as mentioned above, fat cannot be converted into glucose, but it does dramatically delay a blood sugar spikes when paired with carbohydrates. Just like the example above, pizza, the fat from cheese and other ingredients will delay the spike so that the pizza will still be breaking down into glucose much longer than when carbohydrates are consumed alone. High fat content can also induce insulin resistance. That’s also seen when eating pizza and struggling with a delayed, stubborn spike. So it’s important to consider the fat content of food.

As it is pretty obvious above, carbohydrates are the ONE and ONLY macronutrient that significantly impact blood sugar, but protein and fat also play a significant role in HOW carbs are broken down. It can get pretty unpredictable when all three are mixed into the blood sugar equation. It’s not just counting carbohydrates!

Because of this, and Dr. Bernstein’s book, linked below, I’ve modified my eating habits and created a new lifestyle, low carb high protein. My blood sugar is substantially easier to control. I still eat delicious foods (just low carb versions), and I generally spend much less time brewing over my diabetes than I did when I ate everything I ever wanted to and just “took insulin”. That approach does not work for the VAST majority of diabetics, and I belong to that group.

Eating low carb has saved my life, maybe not today, but for the future.

Control is not a sacrifice, it is a lifestyle.

In closing, I thought I would share my absolute favorite quote from Dr. Bernstein’s book, Diabetes Solution, as it directly relates to macronutrients:

There are essential amino acids and essential fatty acids, but there is no such thing as an essential carbohydrate.

Do you face any challenges with calculating insulin needs for carbs, fat, and/or protein? What approach do you use?


P.S. An important reminder:

Taking insulin for protein, fat, and carbohydrates can be really difficult and confusing. A lot of it is also trial and error. Please remember that I am not a medical professional and the discussion above is based on my own experience. You should always consult with your doctor before initiating any changes, including what was discussed above. 



  1. Thank you for sharing! I’ve learned that with time too (my son has diabetes) with pizza, works perfect to him bolus 40/60 at 6 hours, and don’t see any spike 🙂 and croissant, 50/50 one hour…. I haven’t tried with mayor protein. I would like to know which polialcohol do you use at most?


  2. Hi! could you share your insulin ratio for the protein? OR do you use the same ratio as for your carbohydrates? (I mean; how much mmol insuline per gram of protein? Thanks a lot for this amazing useful insight by the way 🙂


  3. Note that these articles from 2012 & 2015 and delivered at major diabetes forms

    Dr. Wolpert was my doctor and never mentioned this until I brought up my own issues with these topics so why am I not surprised by other doctors not speaking or even knowing about this.

    Impact of fat, protein, and glycemic index on postprandial glucose control in type 1 diabetes: implications for intensive diabetes management in the continuous glucose monitoring era.
    Bell KJ, Smart CE, Steil GM, Brand-Miller JC, King B, Wolpert HA.
    Diabetes Care. 2015 Jun;38(6):1008-15. doi: 10.2337/dc15-0100. Review.
    PMID: 25998293

    Dietary fat acutely increases glucose concentrations and insulin requirements in patients with type 1 diabetes: implications for carbohydrate-based bolus dose calculation and intensive diabetes management.
    Wolpert HA, Atakov-Castillo A, Smith SA, Steil GM.
    Diabetes Care. 2013 Apr;36(4):810-6. doi: 10.2337/dc12-0092. Epub 2012 Nov 27.
    PMID: 23193216


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