Serving To Educate Primary Care Clinicians On Metabolic Issues
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Back: Carbohydrate Counting

By: Teresa L. Pearson, MS, RN, CDE
Director, Diabetes Care
Fairview Health Services
Minneapolis, MN 

For some people, health care providers as well as people with diabetes, carbohydrate (CHO) counting is considered a foreign language. Difficult to teach and difficult to understand. It is also something that not all people with diabetes need to do. However, because it is known that the quantity and source of carbohydrates are major determinants in blood glucose, particularly post-prandial blood glucose, a basic understanding of carbohydrates is important to all people with diabetes to help them improve their glycemic control.

Basic Nutrition Guidelines 

So where to start? For most people with Type 2 diabetes, a basic knowledge of nutrition guidelines is enough. According to the American Diabetes Association, a meal plan should be individualized with consideration for the patient’s lifestyle and culturally appropriate foods. Nutrition counseling should include:

  • 3 balanced meals and snacks each day
  • Eating about every 3 - 4 hours to minimize extremes in blood glucose excursions
  • Choosing concentrated sugars in small amounts
  • Eating foods high in fiber
  • Limiting saturated fat intake to < 7%
    Especially limit trans fats
  • If alcohol is consumed, do so only in moderation

Once the patient is on insulin, including a recognition of what is a carbohydrate and portion sizes may be all they need to know. To take it one step further:

  • Monitoring CHO remains a key strategy in achieving glycemic control
  • The use of glycemic index and glycemic load MAY provide an additional benefit for glycemic control

There needs to be an understanding of the impact of carbohydrates, proteins and fats on blood glucose and what happens if the amounts change from day to day. Basically fats and proteins have little or no impact on blood glucose other than possibly slowing the impact of carbohydrates in a mixed meal or food. Carbohydrates become 100% glucose in the blood and get into the system in anywhere from 15 minutes to an hour depending on the complexity of the carbohydrate and if it is mixed with a fat and/or a protein. For the most part, this is too much information for your usual patient. The bottom line is, carbohydrates cause blood glucose to rise. How much one cup of pasta raises my blood glucose compared to yours is individual and the only way we will know is to test postprandial blood glucose 2 hours after the meal and keep records.

If the patient is on an oral agent that does not cause hypoglycemia, this may be all they need to know. Even if they are on a long-acting insulin as their basal insulin. However, if the oral agent is a sulfonylurea or if their basal insulin is NPH, they will need to pay closer attention to carbohydrates. Typically for this type of patient with a fairly regular schedule, the easiest approach would be to ask them to eat about the same amount of carbohydrate every day at about the same time every day. This will help eliminate extreme fluctuations of blood glucoses due to increased or decreased amounts of carbohydrate. The same approach could be used for someone on pre-mixed insulin, eliminating the need to do any calculations. You will likely need to do some tweaking of the dose to come up with the right dose for the amount of carbs but this should eliminate the need to do daily calculations as long as food and activity remain consistent from day to day and at about the same time every day. If there are changes in blood glucose with this regimen, you will need to determine if there have been any changes in the schedule and portion sizes. If these have remained constant then other causes need to be looked at such as a possible illness or infection. It is also expected that the patient will not remain on the same dose over a long period of time even with consistency in schedule, food and activity, simply because diabetes is a progressive disease. This is the one thing we know for sure, regardless of the patient and regardless of the level of control today, if all things remain constant, diabetes WILL progress with age. So it is not only common, but it is expected that regimens and doses will change over time.

Resources for Nutritional Information

In addition to referring your patients to a diabetes educator, resources that will help with teaching your patients about carbohydrates are using nutrition labels from some of their favorite foods. It is important to tell your patients that the front of the label is for marketing purposes only and can be misleading. The nutrition label on the BACK of the package is where they need to look and for carbohydrates, always look at TOTAL carbohydrates. Do not subtract sugar alcohols or fiber.

Websites such as as a resource for finding the composition of just about any food you can imagine, can be very helpful. Additionally, nutritional information for menu items at most fast food and chain restaurants are available online and would be helpful for those who eat out a lot.  

It is also helpful to ask your patient to bring in a food log from three typical days. Ask them to try to estimate amounts as well as types of food and times of eating so that you will get a sense of how erratic or consistent their schedule is from day to day. It will be helpful to refer them to a dietitian for help with this.

Carbohydrate Counting

Once a patient is on multiple daily injections of insulin, a pump and/or has an irregular schedule, you may want to discuss with your patient whether it is time to consider carbohydrate counting. The biggest advantage to carbohydrate counting is that it allows for flexibility. For the on-the-go person whose schedule varies from day to day, this is the way to go. First, assess the patient’s numeracy and literacy. They will need to be able to do some simple calculations and some estimation of portion sizes and commit to testing and record-keeping. Some people will grasp this concept readily and others may revise it and simplify it to meet their own needs.

To do carbohydrate counting the patient will need to have a solid understanding of:
  • What is a carbohydrate and how to count carbs even in a mixed meal
  • How to estimate portion sizes
  • The insulins they are taking and the onset, peak and duration of the insulin
  • How much insulin they need to cover their carbohydrate intake (this varies from patient to patient)
  • How much one unit of insulin will reduce their blood glucose (this also varies from patient to patient)
  • The  concepts of insulin on board to avoid stacking of insulin

The patient will also need to commit to monitoring their blood glucose before every injection. This will help ensure they stay in a safe glucose range. 

Total Daily Dose

To transition to multiple daily dose insulin using carb counting, begin with their total daily dose, as follows:

  • Initially Total Daily Dose (TDD) should be divided into 50% basal & 50% bolus
  • Start low and go slow
  • Titrate using patient’s self blood glucose monitoring

The Value of a Unit of Insulin 
  • Correction Factor (CF)
    How much one unit of insulin will lower the blood glucose for this individual
  • Insulin to Carb Ratio (I:CHO)
    How many grams of carbohydrate one unit of insulin will cover while keeping blood glucose in range

Calculating the dose

Easy math – these rules of thumb have been supported in the literature.

  • 1800 ÷ by TDD  =  Correction Factor (CF)
  • 500 ÷  by TDD = Insulin to carb ratio (I : CHO)

The basic premise of carbohydrate counting is that the insulin dose is matched to the amount of carbohydrate ingested.  And blood glucose monitoring is done to determine if the calculation was correct and if not, it will be adjusted the next time.

To be certain your patient fully understands the concept of carbohydrate counting, ask your patient to do some simple calculations of carbs either using their own food log or some examples you give them. For example:

If Joe eats a grilled chicken breast sandwich with cheese, lettuce and a special sauce, plus a handful of chips and a green salad with about ¼ C of ranch dressing and an unsweetened iced tea, how much carbohydrate is he eating? Let’s break it down.
  • Grilled chicken = no carb
  • 2 slices bread = 30 grams
  • 2 slices swiss cheese = no carb
  • 2 lettuce leaves = no carb
  • Special sauce = no carb
  • Handful of chips = about 15 grams carb
  • Salad with ranch dressing = no carb
  • Unsweetened iced tea = no carb
Total carbohydrate = 45 grams 

So now to determine how much insulin to take for that meal we use carb counting.
Dosage of insulin is based on total grams of carbohydrates. For example:

  • If the insulin: CHO ratio is 1:15
    If the total grams of CHO is 45, then 3.0 units of insulin would be administered
  • If the insulin: CHO ratio of 1:10
    If the total grams of CHO is 45 then 4 or 5 units of insulin would be administered – typically, we would round down to be safe unless the patient is highly insulin resistant.

There are two things to keep in mind. This will always be an estimate. Portion sizes are estimated and number of grams for those portions is estimated so it is probably safest to round down. On the other hand, as people eat similar meals from day to day, they will become familiar with how their body responds to a chicken sandwich vs a similar portion of pasta or pizza. This does get into the concept of glycemic index which is too complex for most patients so best to not go there and just allow them to do the estimate and then keep records so they will be able to track how they respond to similar meals. 

More Examples

Which of these has 45 grams of carb?
  • A tuna sandwich, 10 chips and an unsweetened iced tea
  • Two 6-inch chicken tortillas with ½ cup rice and a diet drink
  • Half a turkey sandwich with a small apple and a cup of skim milk
  • All of the above 

The correct answer is: All of the above.

How many grams of carbs are in a meal of a half glass of juice (4 oz), 2 pieces of toast, 3 slices of bacon and 2 eggs?

  • 45
  • 120
  • 30
  • 20

The correct answer is: 45.


First of all – find a diabetes educator who can spend the time with your patient to provide diabetes self management education including nutrition therapy.

To help your patient get started they must do the following:
  • Become familiar with weighing and measuring foods accurately
  • Read food labels
  • Access resources for foods including those w/o labels –  
  • Keep food records
  • Eat, test,, test,, test, record...
And remember:
  • Customizing lifestyle management results in improved adherence  and better outcomes