How to count carbs for Type 1 diabetes

One of the biggest barriers to managing Type 1 diabetes comes down to annoying math. Learn how to count carbs to master the insulin-to-carb ratio.

I have lived with Type 1 diabetes for 21 years. Carbohydrate counting is as integral to a meal to me as chewing. And that’s because there’s a lot of math to think about when you sit down to eat when you have diabetes: You have to count carbohydrates (carbs) and calculate your insulin-to-carb ratio. It can be a lot, and it can be easy to become frustrated sometimes. Carbohydrate counting is both a science and an art –– let’s discover it.

Diabetes management has three pillars: checking your blood glucose (blood sugar) regularly, insulin delivery and counting carbs. Each one of these is as important, and they are all interconnected and related. You can do a sliding scale or set dose of insulin, but if we don’t count carbs, it’s likely that we won’t have the best blood sugar levels we could have.

If you take carb counting out of the three pillars, we would start to see our blood sugar be affected because we are not getting the correct dose of insulin.

Examples of carbs

Before we get started, what are these carbs that we’re going to be counting? Examples of foods with carbohydrates include:

  • Any and all fruit
  • Breads, pasta
  • Starchy vegetables such as peas, corn, potatoes
  • Anything that contains sugar

Insulin-to-carb ratio: How carbs work for Type 1 diabetes

Wendy Novak Diabetes Institute

Norton Children’s Endocrinology, affiliated with the UofL School of Medicine

Type 1 and Type 2 diabetes care

When we eat carbs, they are digested and broken down into glucose into our bloodstream, which in turn raises our blood sugar. When we deliver insulin into our body, it lowers our blood sugar. Our goal is to use a calculation that matches the two: So, we take the correct amount of insulin for the correct amount of carbs that we’ve eaten to have the best blood sugar levels possible after we eat. This is called the insulin-to-carb ratio. This means 1 unit of insulin will cover a certain number of grams of carbohydrates.

Here’s an example: Say your insulin-to-carb ratio is 1 unit of insulin for every 10 grams of carbs. You are having 60 grams of carbs at lunch. You take 60 (amount of carbs eaten) divided by 10 (your unit of insulin per 10 carbs, as recommended by your endocrinologist) and you will take 6 units of insulin before you eat lunch.

Insulin works in the body for about three hours, and the goal is that within the three-hour window after eating, that your blood sugar may rise slightly but return to normal, or have little to no rise at all. If your blood sugar rises and stays high after correctly counting your carbs and dosing according to your insulin-to-carb ratio, you’ll want to talk to your endocrinologist about adjusting your ratio numbers.

Why is carb counting important?

A study by Barton Center for Diabetes Education Data Center looked at 48 individuals, ages 12 to 18. Participants were given a carbohydrate estimation survey. Only 23% of them were able to estimate within 10 grams the true amount of carbs in a food. This age group may be newly diagnosed, or they just now are gaining their own independence with their care and diet management. The individuals who most accurately estimated their carbs had the lowest A1C levels, a measure of blood sugar. There is a strong correlation between knowing carb counting and overall A1C blood sugar control.

Carb counting resources

There are many resources to help children and families count carbs.

Here’s an example:

  • Nutrition labels –– most accurate way to measure carbs
  • Apps and carb counting books
  • Large-scale restaurant websites that provide nutrition information
  • Online search engines such as Google

How to read a nutrition label for carb counting

If we look at our nutrition label, there are two things we want to look at, and only two. First is “serving size,” and the second is “total carbohydrate.”

For example, if a food label says a serving size is 1/2 cup, and total carbohydrates equal 13 grams, there are 13 grams for each 1/2 cup eaten. If you eat a cup, you’ll have consumed 26 grams of carbs.

A few ways people may make errors when reading nutrition labels is to equate the sugar with carbohydrates. Especially when a person with Type 1 diabetes is newly diagnosed, sugar can seem like the scary thing you need to stay away from. However, let’s say there are 3 grams of sugar in the food example we just explored. If you eat 1/2 cup and dose for 3 grams of sugar instead of the 13 grams of carbohydrates, you’ll miss out a large dose of insulin.

Another issue for nutrition label reading for people with Type 1 diabetes is the concept of “net carbohydrates.” This concept is spread widely through health blogs as well as in the Type 2 diabetes community. It’s the idea of subtracting the total amount of dietary fiber from the total grams of carbohydrates. While this is a good technique for people living with Type 2 diabetes, it can cause children with Type 1 to get less insulin than they need for the amount of carbs they’ve eaten.

Carb-counter apps

This is a great resource for access to carb counting for children and their families no matter where you are. These are some of the most popular carb-counter apps to get nutritional data on the go, with information on generic foods as well as many brands and major restaurants:

  • MyFitnessPal
  • Carb Manager
  • CalorieKing
  • SparkPeople

Some of these include other functionality, such as blog posts, food diaries, water tracking, etc. Those other functions may be helpful for you depending on the goals set by you and your diabetes care team. My favorite, however, is CalorieKing, since it is strictly for looking up macronutrients for foods. It was founded in 1973; its first book was published in 1983, so the information predates the app era. Not only does the app have information for restaurants and basic foods, it has information for homecooked meals. Let’s say we’re eating our granny’s mashed potatoes; we can select “mashed potatoes” and choose “home prepared with whole milk.” A cup of our granny’s mashed potatoes will set you back 35 carbs. But if you want to have a smaller serving size, you can adjust to estimate carbs. There’s a lot of customization and information that these apps can provide you. But from time to time, you’ll encounter some situations that cause issues.

The internet has a wealth of information for carb counting as well. Never heard of a food before? Look it up online. While searching many foods, a nutrition label will appear with all of the macronutrients listed. Chain restaurant websites also list the nutrition information for menus, and may include functionality that allows you to virtually build your meal and provide you with a macronutrient count based on your order –– this can help you plan your dose and your meal before you go –– as long as your portion sizes look right.

Measuring portion sizes for carb counting on the go

We’re not always the best at estimating portion sizes; and we don’t always carry measuring cups with us when we’re out and about. But using our hands as a visual portion guide while we’re out to eat can help us gauge how much we’re about to eat to start our carb counting. For example, you go to a steakhouse and get a steak with mashed potatoes and broccoli as sides. The size of the steak and the serving size of broccoli and mashed potatoes aren’t uniform. Your best guess using your hands can help you estimate your portions:

  • Front of your closed fist: 1/2 cup
  • Clenched fist: 1 cup serving
  • Palm of the hand: 3 to 4 ounces, standard serving of meat
  • Fingertip: 1 teaspoon
  • Thumb: About two tablespoons (Measure one tablespoon from your knuckle to the tip of your thumb)