Carb counting with diabetes: A first hand overview

Note: I am not a healthcare professional or a dietician. The information in this article is based on my knowledge and experience. This is not designed to be a substitute for the advice your healthcare team provide you with.

Carbohydrate counting is a skill which you should definitely invest some time to master.

What are carbohydrates?

Carbohydrates, proteins and fats are regarded as macronutrients.

Carbohydrates are classed as simple or complex. The main difference between the two is how quickly the sugar is absorbed and digested into the blood. When digested, carbohydrates are broken down into sugars. Simple carbohydrates contain only one or two sugars and so therefore are digested and absorbed by the body very quickly. Complex carbohydrates on the other hand have three or more sugars and can be referred to as ‘starchy foods’.

Below is a graph which illustrates what happens to your blood glucose when you eat different food groups.

What is carbohydrate counting?

Carbohydrate counting involves taking into account the carbohydrate content of a food when determining the amount of insulin to give.

When I was first diagnosed, carb counting was not part of my diabetes management. As I got older and left the honeymoon period, I began a regime of daily basal and bolus injections. Instead of injecting a set amount of insulin at certain times of the day to cover my meals, I began to take bolus (fast acting) injections each time I consumed food.

This insulin would counteract the rise in my blood glucose from eating carbohydrates and would help maintain my blood glucose within its normal range.

Getting the hang of carbohydrate counting can be a long and daunting task. It took me many years before I was completely confident in my ability to bolus with carbohydrate content in mind. However, carbohydrate counting can offer you so much freedom when it comes to managing your diabetes.

Two main benefits of carbohydrate counting:

  • Tighter control of blood glucose

  • Flexibility with meals

As you can see from the graph above, consuming carbohydrates has a direct impact on your blood glucose compared to that of protein and fats. It’s for this reason that being aware of the carbohydrates in your foods is critical for good control. Being on pens or a pump and having little knowledge about the effects of carbohydrates can lead to dangerously erratic blood glucose levels, which in turn contributes to complications later down the line.

For example, not knowing that a 1L bottle of regular coke has around 120 g of carbohydrate could land you in a nasty situation if you fail to bolus enough insulin to cover it (or maybe just don’t have regular coke…)

How does carb counting work?

Carb counting works by matching an insulin dose to the amount of carbohydrates you consume through food or drink. The amount of insulin someone needs to ensure their blood glucose remains within normal range after eating may vary, and so knowing how much insulin you need to cover carbohydrates is necessary for good management.

For example:

Florence has Type 1 Diabetes. For breakfast, Florence consumes 50 g worth of carbohydrate. She knows she must bolus 5 units of insulin to cover this meal to keep her blood glucose within range.

Why does Florence inject 5 units of insulin?

Florence knows that her carbohydrate:insulin ratio is 1:1. This means that for every 10g of carb that she eats, she must inject 1 unit of bolus (fast acting insulin).

Unfortunately, carb counting is not always as simple as this. Not only do ratio’s differ between diabetics, but ratio’s may also differ depending on the time of day.


  • Morning - 1:1 ratio. (10 g of carb requires 1 unit of insulin)

  • Afternoon - 1:2 ratio. (10 of carb requires 2 units of insulin)

  • Evening - 1:1.5 ratio. (10 g of carb requires 1.5 units of insulin)

The ratio’s you require depend on different factors, such as:

  • Weight

  • Age

  • Activity levels

  • Insulin sensitivity

As everyones ratio is different, your healthcare team will be the ones to decide with you where to start. I started off on a basic ratio, such as 1:1, and went from there.

Another example:

William knows that for dinner, each 10 g of carbohydrate he consumes requires 2 units of bolus insulin. He decides to eat pasta and garlic bread, which totals to 120 g of carbohydrate. He knows that he needs a total bolus dose of 24 units. As Will is on an insulin pump, he decides to extend this dose over 2 and a half hours.

How do I know what foods I need to inject for?

Carbohydrate counting is something a dietician or your healthcare providers will talk you through and explain completely. Before going on an insulin pump, you may be required to complete a DAFNE course (Dose Adjustment for Normal Eating).

I’ve personally done a short version of this course. It takes you through what carbohydrates are, what foods contain them, and how carbohydrate:insulin ratio’s work.

What kind of foods will I need to consider when it comes to carb counting?

Anything with carbohydrates in.

For example:

  • Oats

  • Bread

  • Sauces

  • Jam

  • Honey

  • Biscuits

  • Crisps

  • Juices

  • Milk

  • Chocolate

  • Sweets

  • Cereal

Foods I don’t bolus for (but others might)

  • Meats

  • Egg

  • Some vegetables

  • Nuts

  • Fish

  • Oils

  • Butter

  • Black coffee

  • Diet drinks

So I know what foods have carb in them... but how much carb is in this portion I'm having?

When I was learning to carb count, I was introduced to an amazing book & app known as 'Carbs & Cals'. This book/app was a game changer for me. Like most people, I never really considered the nutritional information of foods before eating them. Only when it became absolutely necessary (carb counting for insulin) did I purchase this book/app to learn more about the foods I eat.

Carbs & Cals features hundreds of different foods and portion sizes. It includes realistic meals, snacks, sides and drinks that we consume everyday. In fact, there have been a load of foods on there which I never thought about before I got the book/app. One of the most useful things on Carbs & Cals is take-away coffee, such as a Costa latte, for example. I always used to guesstimate how much carb was in the coffee I was having until I started using Carbs & Cals.

If you're new to carb counting, or perhaps want a quick, on the go resource to help you calculate the insulin dose you need, Carbs & Cals is perfect for you. It is also PERFECT for takeaway foods and restaurant meals.

Click below to check it out! (Currently on discount at time of post)

Reading food labels

On the back of many food packages you’ll see the nutritional information in the form of a table. When carbohydrate counting, you need to focus on the carbohydrate content for the portion size you’re going to be having (NOT the ‘of which sugars’).

For me personally, I would have to inject 3 units of bolus for this meal, as my ratio is 1:1.

What if it doesn't tell you the portion size on the label?

On some food packaging, you'll find that the carbohydrate value per portion is not clear, and gives you the value per 100 g instead. This is where a bit of maths comes into play.

Let's say you saw the label to the right on the back of a pack of pasta. What you would first need to do is weigh out the amount of pasta you plan on consuming. In this case, let's say 60 g.

We know that 100 g of pasta equates to 45 g of carb (I'd like to get my hands on this pasta...). What we must first do is work out how much carb is in 1 g of pasta.

The calculation will be: 45/100 = 0.45 (1 g pasta) ... 0.45 (1 g) X 60 = 27 g of carb.

We know that in 1 g of pasta there is 0.45 g of carbohydrate. So to work out how much carbohydrate is in 60 g of pasta, we must multiply 0.45 by 60, which gives us the value of 27 g of carbohydrate in our desired portion of pasta.

At this point you would then need to calculate the amount of insulin you require for this amount of carbohydrate. For me, I know that my ratio of carbohydrate:insulin is 1:1, so for the 27 g of carbohydrate in the pasta, I will be bolusing 2.7 units of insulin.

Keep in mind that everyones ratio's could be different. If you are unsure about how much insulin to inject, you must consult your diabetes team and/or healthcare professionals. Getting your ratio wrong or simply guessing could result in either hypo or hyper.

Last tips for carb counting:

Learning to carb count is very trial and error. You can learn the basics (as I've discussed here), but like diabetes in general, you learn the most from experience.

Here are some finishing tips I use daily when carb counting for a bolus:

  • If unsure, use resources like Carbs & Cals (see link above). It's an absolute life saver and covers nearly every food and drink you can think of. It's amazing.

  • Try not to guess. Guessing the amount of carbohydrate in something never usually ends well. Unless you're someone who's been carb counting for 8+ years (like me), it's unlikely that you're going to know the amount of carbohydrate in every food. Save yourself the stress of a hypo or hyper and work out how much carb you're eating.

  • If I really can't find the amount of carbohydrate in a food or drink, I will always bolus for less than I think I should. I'd rather correct for a high than shove my face for a low.

  • If you find that your blood glucose is still elevated hours after bolusing for food, it might be that your ratio is off. It can be tempting to adjust your ratio yourself without the guidance of your healthcare professionals. If you're new to carb counting, or don't yet consider yourself a master of the sport, don't start adjusting freestyle. In the past this has made my control go crazy. Always seek medical support.

If you're interested in learning more about how I've managed to maintain an excellent HbA1c over the years, take a look at my Diabetes, Diet & Exercise eBook guide.

Diabetes, Diet & Exercise

My first hand account of T1D, diet & exercise is aimed at older teenagers and above. The foods we eat and our level of activity have a direct influence on the behaviour of our blood glucose. Finding the foods that keep your blood glucose stable and unproblematic is a long process. Everyone is different and for that reason fine tuning your diet is a very personal journey.

We all want to make sure we fit into our favourite jeans, don't we? Exercise has a very important role in both blood glucose control and weight management. Regular exercise can really help lower your insulin sensitivity and stabilise your HbA1c.

Learn the following:

  • An overview of diet How different foods effect your blood glucose

  • How I inject depending on the foods I eat

  • How I stop spikes in blood glucose after fatty foods

  • How excess insulin causes weight gain and how I stop this from happening to me

  • Diabulimia

  • My rules to losing fat with Type 1 Diabetes

  • Foods I eat and foods I avoid to lose weight & maintain good glucose control

  • How different types of exercise impact blood glucose

  • Avoiding hypo's during and after a workout

  • Fasting

  • Weight training




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