General maths help wanted please for Insulin to carb ratios and how many units of insulin for the meal

[mum2westiesGill]

This thread isn't for me to change my meal ratio of 1:10 it's just for my own general interest and because yes you've guessed it I'm hopless at maths

So 1:10 aka 1u of insulin to or for every 10g of carbs
20g of carbs in the meal divided by 10g of carbs = 2 units of insulin for the meal
25g of carbs in the meal divided by 10g of carbs = 2.5 units of insulin for the meal

1:15 aka 1u of insulin to or for every 15g of carbs
20g of carbs in the meal divided by 15g of carbs = 1.333.....units of insulin for the meal
25g of carbs in the meal divided by 15g of carbs = 1.666.....units of insulin for the meal

1:20 aka 1unit of insulin to or for every 20g of carbs
20g of carbs in the meal divided by 20g of carbs = 1u of insulin for the meal
25g of carbs for the meal divided by 20g of carbs = 1.25 units of insulin for the meal

but how would you work out
0.5:10 aka 0.5units of insulin to or for every 10g of carbs
1.5:10 aka 1.5units of insulin to every 10g of carbs
0.5:20 aka 0.5units of insulin to or for every 20g of carbs
1.5:20 aka 1.5units of insulin to or for every 20g of carbs
etc

 

[Lucyr]

I’d just stick to using ratios where the second number (carbs) changes and the first (insulin) stays at 1 to keep things simple for yourself.

 

[mum2westiesGill]

I’d just stick to using ratios where the second number (carbs) changes and the first (insulin) stays at 1 to keep things simple for yourself.

Is that what most people do so 1:10, 1:15, 1:30?
If you don't mind me asking what's yours? It's probably a complicated one now haha

 

[Lucyr]

Most people stick to one of two methods, where they either do x units to a CP or 1u to x carbs, and only x changes, they don't usually mix and match. I have different ratios for different times of the day and activity levels, between 1:6 and 1:20

 

[Bruce Stephens]

Is that what most people do so 1:10, 1:15, 1:30?

That's usual, yes. (And people might well have 1:5, etc., if they need 1 unit for 5g.)

 

[mum2westiesGill]

That's usual, yes. (And people might well have 1:5, etc., if they need 1 unit for 5g.)

So
32g of carbs for the meal
÷ 5g
= 6.5u of insulin bolus

55g of carbs for the meal
÷ 5g
= 11u of insulin bolus.......

 

[Bruce Stephens]

So
32g of carbs for the meal
÷ 5g
= 6.5u of insulin bolus

55g of carbs for the meal
÷ 5g
= 11u of insulin bolus.......

Yes. (Though 6u would be closer for the first one.)

 

[mum2westiesGill]

Yes. (Though 6u would be closer for the first one.)

Thanks @brucestephens

 

[Sally71]

0.5 unit for 10 carbs would be the same as 1:20
Easiest to keep it 1 unit to whatever.
Most people start on 1:10 which is easy to calculate, you are very lucky if you stay on that.
When my daughter was little she was 1:17 for a while, thank heavens for bolus calculators, I couldn’t do that in my head!
At the moment she’s 1:9, for a while we found 1:7 was too much and 1:8 not enough so I thought I’d try 1:7.5. Except Accu Chek Combo bolus calculator wouldn’t allow fractions so I had to tell it she was 2:15 which is the same thing lol (2 units to 15 grams)
New pump is much more sensible and will allow 1:7.5 but she doesn’t need that any more!

 

[mum2westiesGill]

0.5 unit for 10 carbs would be the same as 1:20
Easiest to keep it 1 unit to whatever.
Most people start on 1:10 which is easy to calculate, you are very lucky if you stay on that.
When my daughter was little she was 1:17 for a while, thank heavens for bolus calculators, I couldn’t do that in my head!
At the moment she’s 1:9, for a while we found 1:7 was too much and 1:8 not enough so I thought I’d try 1:7.5. Except Accu Chek Combo bolus calculator wouldn’t allow fractions so I had to tell it she was 2:15 which is the same thing lol (2 units to 15 grams)
New pump is much more sensible and will allow 1:7.5 but she doesn’t need that any more!

1:17
20g of carbs in the meal
÷ 17
= 1.764.....units of insulin

1:9
20g of carbs in the meal
÷9
= 2.222.....units of insulin

1:7
20g of carbs in the meal
÷ 7
= 2.8571.....units of insulin

1:8
20g of carbs in the meal
÷8
=2.5units of insulin

1:7.5
20g of carbs
÷ 7.5
= 2.6666.....units of insulin

If I've got them all correct

 

[rebrascora]

That first one, the 1:17 ratio looks wrong Gill.

17 goes into 20 once with just 3 left over. 3 is a lot less than half of 17 so you would only need 1 unit of insulin for 20g carbs with that ratio.
The actual result would be 1.176 rounded up to 3 decimal places but that really is going too far when you can only inject whole or half units, so it would be 1 unit.

 

[mum2westiesGill]

That first one, the 1:17 ratio looks wrong Gill.

17 goes into 20 once with just 3 left over. 3 is a lot less than half of 17 so you would only need 1 unit of insulin for 20g carbs with that ratio.
The actual result would be 1.176 rounded up to 3 decimal places but that really is going too far when you can only inject whole or half units, so it would be 1 unit.

Thanks yes I am wrong it's what you said 1.176.....
What about the others?

 

[khskel]

Look ok to me. I find a bit of approximation helps to check the reasonableness of the answers i.e
With the 1:7 we know that 3x7 is 21 so your answer of 2.8571 looks sensible had you got an answer greater than 3 it would definitely be wrong.

 

[mum2westiesGill]

Look ok to me. I find a bit of approximation helps to check the reasonableness of the answers i.e
With the 1:7 we know that 3x7 is 21 so your answer of 2.8571 looks sensible had you got an answer greater than 3 it would definitely be wrong.

Thank you!

 

[mum2westiesGill]

So as you can see in my posts above I know the sum of how to work out the 1unit of insulin:grams of carbohydrates ie 1u:10g, 1u:8g, 1u:20g etc but how do you work out 1.5u:grams of carbohydrates? (1.5u:10 grams of carbohydrates)

 

[silentsquirrel]

So as you can see in my posts above I know the sum of how to work out the 1unit of insulin:grams of carbohydrates ie 1u:10g, 1u:8g, 1u:20g etc but how do you work out 1.5u:grams of carbohydrates? (1.5u:10 grams of carbohydrates)

Why would you want to, Gill? Sticking to ratios of 1 : something makes life much easier!

If you insist, make the 1.5 into 1 by dividing both parts of the ratio by 1.5. So 1.5 : 10 = 1.5/1.5 : 10/1.5 = 1 : 6.67

 

[Leadinglights]

So as you can see in my posts above I know the sum of how to work out the 1unit of insulin:grams of carbohydrates ie 1u:10g, 1u:8g, 1u:20g etc but how do you work out 1.5u:grams of carbohydrates? (1.5u:10 grams of carbohydrates)

 

[Leadinglights]

So as you can see in my posts above I know the sum of how to work out the 1unit of insulin:grams of carbohydrates ie 1u:10g, 1u:8g, 1u:20g etc but how do you work out 1.5u:grams of carbohydrates? (1.5u:10 grams of carbohydrates)

You might find it useful to get a piece of paper on which you can make a reference table of all the ratios you might want to use. Then you could stick it up on the fridge door.
So for 1.5u for 10g carb, divide number of g of carb you are having by 10 and multiply that number by 1.5 = number of units you need
e g for 50g carb
divide 50g by 10g = 5 multiply by 1.5u = 7.5u
for 36g carb
divide 36g by 10g = 3.6 multiply by 1.5u = 5.4u
You can end up with some awkward numbers.

 

[Bruce Stephens]

1.5u:10g is about 1u:7g (a bit less than that). (It's 10/1.5, which is the awkward 6 2/3.)

 

[mum2westiesGill]

You might find it useful to get a piece of paper on which you can make a reference table of all the ratios you might want to use. Then you could stick it up on the fridge door.
So for 1.5u for 10g carb, divide number of g of carb you are having by 10 and multiply that number by 1.5 = number of units you need
e g for 50g carb
divide 50g by 10g = 5 multiply by 1.5u = 7.5u
for 36g carb
divide 36g by 10g = 3.6 multiply by 1.5u = 5.4u
You can end up with some awkward numbers.

Thanks for my 'easy sums' and workings out.
I emailed my DSN about my lunchtime hypers and that my bolus adviser keeps advising a correction at breakfast time - she knows obviously that on her advice I only correct over 10mmol so I keep dismissing the advised correction dose. I asked about changing my breakfast ratio from 1:10 to 1:8 which is what a forum member suggested but my DSN has suggested changing to 1.5:10 - as you showed me in your example for 36g of carbs in the meal that would be 5.4 units of insulin whereas 1:8 for eg 36g of carbs in the meal would only be 4.5 units of insulin - tell me is there or is there not much difference between the 2 insulin amounts?

Ps yes it would be 'extremely' useful for me to have a reference table for different ratios