Type 1 Diabetes

A Very Basic Guide to Carb Counting

One of the biggest tools to help you with the management of Type 1 Diabetes is carb counting or carbohydrate counting.

Basic Guide to Carb Counting

Before I go any further with this post I have to point out that I am not a medical professional, I am no expert in any way other than my own son having had Type 1 Diabetes for almost 7 years now and us being carb counters ourselves. This is not medical advice, just hopefully helpful. If your Diabetes team haven’t mentioned they will be starting you on carb counting, do double-check with them before starting.

Phew now I know I won’t be getting sued any time soon I can get on with the post ;)

Carb counting for Type 1 Diabetes is when you calculate the quantity of carbohydrates in your meals or snacks and use a pre-worked out ratio to then calculate how much insulin you will need to cover that food. When we were first diagnosed we didn’t carb count, and when they did decide we should, there was a long waiting list for the dietician.

We decided to search online and find out as much information as possible as we could, and in the end gleaning everything together we started carb counting ourselves, so that when I finally had our appointment with the dietician a couple of months later, she was really impressed with how we’d got on and said to just carry on as we were.


Where do I find Carbohydrate information for food?


To actually find out the carbohydrate quantity of any meal or snack, you will need to know how many carbs are in each item. You can find this out by;

Checking the labelling – most packaged food has the carbohydrate quantities per serving or per 100g on them.

Using the Carbs and Cals book or app – you can find out more about on the Carbs and Cals website, our diabetes team actually gave us a Carbs and Cals book, so it may be worth checking if they have a spare for you.

Using other apps – Apps like MyfitnessPal, although intended more for fitness and dieting can come in really handy as they have a lot of carb values on them

Google – For simple items like potatoes, fruit and more if you search google asking ‘how many carbs are in a jacket potato’ etc then the answer will come up at the top of the results.

One thing to bear in mind is, that sometimes looking on different sites you find different carb amounts as some lack accuracy. Carbs and Cals I trust the most in this instance and if all the sites aren’t very different, then I just go for a middle ground number.


How do I work out the carbohydrates in a meal or in a snack when it just says 100g?


It really is very simple to work out the carbs that something contains when you know what 100g of the item is. All you need to do is to divide what ever the number of grams of carbohydrates it says is in a 100g of the item by 100, this will let you know how many carbs are in 1g of the item.

Then you just times that carbohydrate 1g result by how many grams of the item you are having – scales are your best friends when carb counting.

So for instance imagine you are eating something that weighs 54g but the carbohydrates on the label say 15g of carb per 100g.


You therefore do the following sums:


15 ÷ 100 = 0.15

0.15 x 54 = 8.1


Now you know that the thing you are going to eat has 8.1g of carbohydrates in it. The mathematics is the same if you are going to have a portion that weights 59g or 154g etc, you would just replace the last ‘x 54’ with x 59 or x 154 and so on.

You do this for all items you are eating in one sitting – don’t worry it gets easier and quicker once you get used to it and you will reach a point where you can estimate the carbs easily when you need to.

So at this point you know how many carbohydrates you have, if eating more than one thing you do the calculation for all of them and then add them together. Say for example in addition to the item above that was 8.1g of carb, you are also going to eat other things at the same time that are 15g, 9.4g and 28g, then you do this sum:


8.1 + 15 + 9.4 + 28 = 60.5

You now know that the total carbohydrates in what you are eating are 60.5g. Once you know how many carbohydrates you are having you need to use your insulin to carb ratio to work out how much insulin you will need to give.


How can I work out my insulin to carb ratio?


The basic way of doing this, is to start from a set point and monitor levels over a few days to work out whether your ratio needs to go up, down or if you’re lucky stay the same. A good starting point for adults who are carb counting is 1 unit of insulin for every 10g of carb. For children, in my opinion you are better off starting at 1 unit of insulin for every 15g of carb to be safe.

If they are toddlers, I would wait on the doctors and dietitians to help you to learn to carb count personally, as they may need very small amounts of insulin and carb counting may not be a safe thing to try out alone.

Children are smaller and therefore tend to need smaller doses of insulin, although everyone is individual and so are their insulin needs. I just always liked to play it safe with my son and not risk big hypos to start with, but he was 6 (diagnosed at age 5) when we started carb counting, so he was able to tell me when he felt low.

So say you are working out the insulin for a child for the meal above, from the last sum, this is how that sum would go:


60.5 (grams of carb) ÷ 15 (the ratio number) = 4.03


This means that for this meal of 60.5g of carb, using a ratio of 1:15 (1 unit of insulin for 15g of carb) you will need to give them 4 units of insulin.


How will I know if the insulin to carbohydrate ratio is right?


When ever you change or start with an insulin to carb ratio, it is a good idea to leave it at least four days to see if it is working, as this will show if there is a pattern to the blood glucose results that they are having 2 hours or more after their carb counted meal and injection.

If they are having hypos a lot (going low) after the meals, then you know that they need less insulin. For less insulin, your ration number needs to go upwards. So if they are on 1 for every 15g and are going low, try 1 for every 16g and wait four days to see if that helps and then do the same again if not.

If they are going high and need more insulin, then you will want to increase how much insulin they have and therefore lower the ratio to 1 for every 14g and work your way downwards, with a test period of four days in between to see how things are going.

If their levels are pretty even, then you know that the ratio is right and you can carry on with it.


The ratio was working but now it isn’t?!


When dealing with children in particular, growth hormone and the fact that they are getting bigger all the time and have periods of being more active etc etc (a whole host of random reasons believe me), mean that their ratios are likely to need tweaking again sometimes.

Personally if the highs or lows are over night and in the morning, then I first tweak our tea time ratio to see if I can set them up better for overnight. If this doesn’t work, or if there are several ratios that don’t seem to be working then I either raise or lower my son’s long acting insulin (he uses Lantus) accordingly.

It all take a bit of balancing at times and can take time to pin point whether the ratio needs changing or the long acting insulin. Personally I only ever change one ratio at a time, so that I can properly monitor the effects and I would never change the long acting units he has at the same time as any other ratio.


Why is this a ‘basic’ guide to Carbohydrate counting?


You may be wondering why I called it  a basic guide to carbohydrate counting, when it is actually a very long post. This is because in the world of carb counting, not all carbs are created equal. Certain foods like pasta, pizza and pastry will have an effect on blood glucose that doesn’t always make sense in relation to their actual carbs.

This is because some foods act much more slowly on blood glucose levels and can cause highs hours after you’ve eaten them, and others can work quickly then cause a low as very sugary foods don’t take long for our bodies to digest and use as energy. BUT when you first start carb counting, you don’t need to learn everything all at once.

As time goes by you will learn the effects of different types of foods on yours or your child’s body and learn what works for you. It can be a steep learning curve and believe me I don’t know it all myself yet.

If you move on to having a pump, then the carb counting will likely change as well, but since my son is on multiple injections instead I am definitely not an expert in that either.

I really hope you find this very long guide helpful!


Stevie x


  • Jo - Mother of Teenagers

    This is fascinating. I had no idea the whole process was so technical. My husband has Type 2 diabetes so we do a lot of low GI meal planning otherwise he has massive crashes but this is a whole different league. In awe!

  • Plutonium Sox

    Wow Stevie, this must be such hard going b having to do it all the time. What an amazing mum you are. I’m sure this will be super helpful for other people too.

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