ASK GINGER - How do I figure out my insulin-to-carbohydrate ratio?

Ginger Vieira Health Guide May 07, 2009
  • Hey Ginger, How do I figure out what my insulin-to-carbohydrate ratio? I’ve been guessing for a while, too long! And I want to be more precise. -Scott




    Hey Scott! I’m glad you asked J It’s so important to know this, especially because you may have to determine what this ratio is again at different points in your life. Stress, diet, weight gain, activity level, age, etc. are all things that can change your insulin needs, but once you get an initial insulin-to-carbohydrates ratio, it’ll be easier to adjust it as you need to.


    First off, here's one very common approach but it may not work for everyone. It's called the 500 Rule and there's a very good guide to it here. This method doesn't work for me as well, because I've found my body has much higher and almost illogical insulin needs in the morning, but it could be applied to later parts of the day. The 500 Rule implies you'll use th same ratio through the whole day.

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    For another approach...


    How do you count carbs? For some carb-basics and knowledge, check these out:

    Understanding Carbohydrates

    The Carbohydrate Quiz


    WHAT IS AN INSULIN-TO-CARBOHYDRATE RATIO? This is the amount of insulin you need to for a certain gram of carbohydrates. For instance, when I was first diagnosed and still in my “honeymoon phase” of producing a small amount of insulin, 1 unit of insulin would cover 15 grams of carbohydrates in my body. Today, I need more insulin, so during the middle of the day, 1 unit of insulin covers me for about 7 – 10 grams of carbohydrate.


    At breakfast, I need A LOT of insulin because of all the hormones being produced when we get out of bed, and I use a ratio of about 1 to 4 (1 unit of insulin for 4 grams of carbohydrates). How did I figure this out? When my blood sugar was repeatedly high after a meal, I kept notes on how many carbs I ate and how much insulin I had taken, and gradually adjusted this amount until I saw my numbers where I wanted them to be. Lots of blood sugar checking! But only at first, once you determine your ratio, you won’t have to try nearly as hard to stay in range.

    Step 1: Start with a level blood sugar. You need to start your experiment with a good blood sugar, having not done any heavy activity before or during (anything that will really effect your blood sugar).


    Step 2: Count the carbohydrates in your meal precisely! Try not to use a meal of pizza or Chinese food, anything high in fat, that could cause your meal to digest more slowly. That is something you will adjust for later on after you know your true ratio. Eat a normal amount carbohydrates, like toast or cereal or fruit. It doesn’t have to be an entire meal, just something with at least 15 to 20 grams of carbs.


    Step 3: Do the math!!! Counting carbs involves math. Non-diabetics don’t have to add and subtract before they eat lunch…we do. So, let’s say you’re going to begin with an estimated ratio of 1 to 12 (1 unit of insulin for 12 grams of carbs), and you’re eating a bowl of cereal for breakfast.

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    1 cup of “NoName” Cereal = 24 grams of carbs

    1 cup of skim milk = 13 grams of carbs

    Total carbs = 37 grams

    37 divided by 12 = 3.08 units.


    Okay…so 3 units. Unless you have a super fancy pump that will give you precise decimals of insulin.


    Let’s do another:


    2 slices of cinamon bread = 36 grams of carbs

    1 medium apple = 15 grams of carbs

    2 tablespoons peanut butter = 6 grams of carbs

    Total carbs = 57 grams of carbs

    57 divided by 12 = 4.75 units.


    If you’re using a syringe you could round up to 5, or if you know you’re going to be active, round down.


    Step 4: Check your blood sugar 45 minutes later. And again about 1 1/2 to 2 hours later. If you’re low: you need to increase the amount of carbohydrates you use for one unit of insulin. If you’re high, decrease the carbs.


    Step 5: Do it again! Try this test several times to really narrow down and fine tune. Try it during different times of the day, after different levels of activity if you want to determine your exercise based insulin-to-carbohydrate ratio. And keep good notes!


    YOU WILL NEED TO ADJUST YOUR RATIO SOMETIMES! If I just finished working out, I am not going to use the same ratio for my post-workout meal that I would normally use because exercise increase our sensitivity to insulin and causes our body to use glucose and glycogen more rapidly. So I know FOR MY BODY, that I can often cut my ratio in half for a lower-carb meal. If I’m eating a lot of carbs after working out, I will take 2/3 of my insulin dose. If I just ate something packed with junk, fat, sugar, processed goo…I will increase my carbohydrate ratio, instead of 1 to 10, I will use 1 to 5.


    Different times of day will effect your ratio too. Usually, we're more active during the day so we need less insulin. For my body, I need the most in the morning. This might not be the same for you.


    Talk to your doctor before/after/or during your "experiments" for help while determining your ratio! Carbohydrates are the number one thing that impact your blood sugar, so it is important to understand how they change your blood sugar!