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Type 1 Diabetes Carbohydrate ratios
and making adjustments to the ratio
Introduction
This leaflet has been written for children and young people with type
1 diabetes and their carers.
What is a carbohydrate ratio?
A carbohydrate ratio is expressed as 1 unit of insulin to X number of
carbohydrate in grams and is used to calculate how much insulin you
need with your meals and snacks.
 For example: 1 unit of insulin to 8 grams of carbohydrate means
that for every 8 grams of carbohydrate you give 1 unit of insulin.
In the case of eating 40 grams of carbohydrate your insulin dose
would be 5 units (40 divided by 8). Your expert meter works this out
for you as it has a built in calculator. Knowing your ratios and how to
calculate your own dose of insulin, however, is also important
because it will help you to become more independent and help with
self-management of your diabetes.
Ratios are used at each meal to determine the amount of fast acting
insulin you give. Ratios may be different at each meal depending on
your individual insulin requirements across the day.
How will I know if my ratio is working?
If your ratio is working well, the blood glucose level before you eat
and 2 hours after will be about the same, for example, 5mmol before
food and 7mmol 2 hours later.
As you are a young person it is important to look at your ratios on a
regular basis because the amount of insulin you need for your meals
and snacks will change as you grow.
PI reference:
GHPI1324_07_15
Department:
Dietetics
Review date:
July 2015
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How do I check that my ratio is right?
To do this you will need to have recent blood glucose readings
 Look at one meal at a time
 Look at overall pattern and not ‘one off’ readings
 Record the information over at least 3 days.
This is what you should record in your diary. It is usually best to work
on one meal at a time:
Example meal
Lunch
insulin for 6g carbohydrate
Date
Carbs
(g)
Insulin
bolus
Blood
Glucose
Before
lunch
Ratio 1 unit
Blood
Glucose 2
hours
after
lunch
Comments
Exercise Stress
Illness
Hypoglycaemia
What the readings mean:
 The blood glucose before the meal should be in the normal range
(between 4 and 8) and the blood glucose 2 hours later should not
have changed by more than 3 mmol up or down from your reading
before eating. If the levels are always high before you eat,
please contact your diabetes nurse for advice.
 If the blood glucose level 2 hours after eating consistently goes up
by more than 3 most of the time, you need more insulin when you
eat. To do this, you reduce the grams of carbohydrate for each 1
unit of insulin.
For example: a ratio of 1 unit for 6 grams means that for 65 grams
carbohydrate you would normally take 11 units of insulin.
To have more insulin, change the ratio to 1 unit for 5 grams. This
means that for 65 grams carbohydrate you would take 13 units.
 If the blood glucose level 2 hours after eating consistently goes
down by more than 3 most of the time, you need less insulin
when you eat.
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To do this you increase the grams of carbohydrate for each 1 unit of
insulin:
For example: a ratio of 1 unit for 6 grams means that for 65 grams
carbohydrate you would normally take 11 units of insulin.
To have less insulin, change the ratio to 1 unit for 7 grams. This
means that for 65 grams carbohydrate you would take 9 units.
 If your 2 hour post meal blood glucose level has not increased or
reduced by more than 3 mmols/L then your ratio is correct and no
change is required.
Remember, there are many other factors that affect blood glucose
levels.
Your ratios are stored in your expert meter, you can access them
and make changes to them by following this series of instructions:
Turn your meter on>settings>bolus advice>time blocks>select
appropriate meal time>scroll down to carb ratio>select ratio>increase
or decrease ratio as required>save changes
Worksheet - what would you do?
Lunchtime ratio 1 unit to 12 grams of carbohydrate
Q1. What would you do to your ratio if you were presented with
the results below?
Day
Carbs
(g)
Mon
65
Tues
50
Wed
75
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Insulin
Bolus
Before 2 hours Comments
meal
after
blood
meal
glucose blood
glucose
14.1
21.2
5.5 + 1.5
correction
4
7.8
14.4
6
9.1
13.2
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Answer
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The pattern shows that my blood glucose keeps rising after lunch, I
need more insulin, my current ratio is 1:12, I will change this initially
to 1:10 and check again to see if it is helping or not.
Q2. What would you do to your ratio if you were presented with
the results below?
Evening meal ratio 1 unit to 8 grams of carbohydrate
Day
Carbs Insulin
bolus
(g)
Before
meal
blood
glucose
Mon
55
7
11.1
2 hours
after
meal
blood
glucose
13.2
Tues 60
7.5
8.1
5.2
Wed
10.5
7.4
10.1
85
Comments
Snack one
hour pre
tea
Answers
The pattern shows that my blood glucose level did not rise after meal
by more than 3 mmols/L nor did, it fall by more than 3 mmols/L.
Therefore I do not need to make any changes to my ratio.
I will monitor the effect snacks have on my blood glucose levels, I
may need insulin with my snacks.
Is my correction factor right?
On Monday I was high and instead of my blood glucose coming in to
target it continued to rise. Therefore this should lead you to check
this again and to discuss a change of correction factor to 2.5mmols/l
next time.
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Contact Information
If you have any questions about how to adjust your carbohydrate
ratio, please contact your Diabetes Dietitian or nurse who will be
happy to help.
Tel: 0300 422 5646
Monday to Friday, 8:30am to 4:30pm
E-mail: [email protected]
Further information
Diabetes UK
Website: www.diabetes.org.uk
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