Flexible Mealtime Insulin Dosing and Carbohydrate Counting

To successfully implement flexible meal-time insulin dosing, you will need to learn the following:

Types of Macronutrients

Carbohydrates are a major macronutrient in a balanced diet, alongside proteins and fats. 

More On Carbohydrates

Carbohydrates are categorised as follows: 

1. Sugars

These are simple carbohydrates that are rapidly absorbed, leading to quick increases in blood sugar levels. Common sources include sugar-sweetened beverages like sodas, packet drinks and sweets. 

2. Starches

These are complex carbohydrates that are broken down into simple sugars upon digestion.

Refined grains are starches  which have undergone processing and have lower fibre and nutrient content. They tend to can cause quick spikes in blood sugar levels. Examples include white rice, corns flakes, and products made from white flour, such as white bread.

Whole grains, being less processed and higher in fibre, are the preferred choice, as they help to stabilise blood sugar levels. Examples include brown rice, whole grain bread and oats.

3. Fibre

These are complex carbohydrates that are indigestible and do not contribute to blood glucose increases. They can also slow down the digestion and absorption of sugars.  

Although carbohydrates (sugars and starches) are the main contributors to post-meal glucose rise, avoiding carbohydrates may lead to excessive protein and fat consumption and potentially cause weight gain. A balanced meal following the  healthy plate concept offers long-term health benefits and is more sustainable over time.

You might already be familiar with basic carbohydrate counting using the carbohydrate exchange system. This approach groups foods based on their carbohydrate content, with each exchange equating to 15 grams of carbohydrates. 

Advanced carbohydrate counting goes a step further, focusing on counting carbohydrate intake more accurately in grams. Accurate carbohydrate counting leads to a more accurate dosing of quick-acting (bolus) insulin and thus better glucose control.

In order to accurately estimate the amount of carbohydrates, you will need the following: 

1. Measurement of serving size of the food item you are planning to eat
Measuring can be done by weighing the food item or using household measures such as cups, spoons, or bowls. 

For example: 

• A standard Chinese rice bowl (300ml), tightly packed with rice, contains about 60g of carbohydrates. 
• One cup of milk (250ml) contains about 15g of carbohydrates. 

2. A reference of how much carbohydrates (in grams) per portion size of the food
We have compiled information on the average carbohydrate content of commonly consumed foods for your reference.  

If the food items come with nutrition labels, do refer to it for more accurate carbohydrate counting.

In addition, you can also refer to online reference databases (see next section). 

Grains, Cereals & Breads

Source: HPB Energy & Nutrient Composition of Food

There are many online references for carbohydrate content available. These include websites and smartphone applications, with some specifically focusing on local foods, which can be more helpful.  

It is advisable to cross-reference information from multiple sources to get a more reliable estimate, as different databases or apps might offer varying values.

When using these resources, pay attention to the portion sizes. Makes sure to estimate the carbohydrate amount based on the serving size you are intending to eat.

Here are some resources to start with: 

The insulin-to-carbohydrate ratio or ICR refers to how many grams of carbohydrate one unit of quick-acting insulin can cover.

The ICR varies from person to person and may differ at various times of the day. Working with your healthcare team is key to establishing an accurate ICR for your needs.

When both the ICR and carbohydrate counting are accurate, you will observe that your post-meal blood glucose levels do not rise more than 3 to 4 mmol/L. Additionally, the glucose level should return to pre-meal targets approximately 5 hours after eating (Figure 1).

While carbohydrate content is the primary factor affecting post-meal glucose levels, other food-related aspects also play a role.

The glycaemic index (GI) of a food, for instance, indicates how quickly it can raise blood glucose levels. Foods with a higher GI cause faster increases in blood glucose levels.