Resource 3
Insulin, Part II
Handy Table of the Action
Background
(Check out Part 1 if you haven’t already.)
In engineering/maths, it’s handy to have tables to look up. Well I find it useful, being a maths-y kind of guy, but everyone uses tables anyway:
If you’ve ever looked at the back of a packet of food, then you know how to use tables.
If you’ve ever been to the airport and checked the departure gate, you know how to use tables.
So I thought I’d make an insulin-action table (for my own personal insulin action) so I could know what to expect in the near future for my blood sugars!
(See main Resources page for a link to the file itself).
Time Column
FINAL BGL DROP
Action Model
Giant Table of Numbers!
Step-by-Step
Let’s go through how this works and how I use it step-by-step.
1. Making the Table
In Part 1 I worked out a simple model for how fast the insulin does its stuff in my body. I worked out that my rapid insulin goes for about 4 hours.
For each hour, I worked out a proportion. So hour 1 = 1/8th, hour 2 = 3/8ths, hour 3 = 2/8ths, hour 4 = 2/8ths. Reminds me of pizza!
Let’s imagine how this might work in a table. Say my BGL was 18 mmol/L when I first inject at 7am. Then, my BGL might do the following:
- Hour 1, BGL = 17 (down 1)
- Hour 2, BGL = 14 (down 4)
- Hour 3, BGL = 12 (down 6)
- Hour 4, BGL = 10 (down 8)
So a total fall of 18 to 10 mmol/L (a drop of 8 in total) by 11am.
I created the table in Excel – it is based on pretty simple maths, though I realise not everyone is good at using a database. I start with the total BGL drop (at 4 hours) and work backwards. Eg a full drop of 16 means:
- Hour 1 = a drop of 1/8th of 16 (down 2/16)
- Hour 2 = a drop of 3/8ths of 16 (down another 6/16)
- Hour 3 = a drop of 2/8ths of 16 (down 4/16)
- Hour 4 = a drop of 2/8ths of 16 (down 4/16)
TOTAL DROP = 2/16 + 6/16 + 4/16 + 4/16 = 16/16 (the full drop)
2. Wake up in the Morning to a Beautiful Day
Let’s do a more ‘real-life’ example (I’ll just make it up this time but will put in some real data another time).
Say my BGL was 15 mmol/L when I first inject at 6:30am.
A bit higher than I’d like (I shouldn’t have had that 2nd big piece of Lemon Meringue Pie last night…). I inject my insulin.
3. Check at 8am
I test my BGL at 8am. It’s down to 14 mmol/L. A fall of 1 mmol/L.
OK, now I look at the table and find 1.5 hours and move along.
Hmm, I see that a fall of 1 mmol/L after an hour-and-a-half could eventually lead to a drop of about 3 mmol/L after 4 hours (i.e. down to 12 mmol/L).
That’s good to know. It looks unlikely I’ll be having a hypo before lunch, unless I did something to make the BGL drop faster than expected.
4. Options if BGL looking high
I could do a few different things here if I wanted to:
- Keep checking BGL and see how accurate the model is at different time points.
- Go for a quick walk if I want to get my BGL a bit lower.
- Do nothing for now, but check BGL again after 2.5-3 hours and then decide something.
- Maybe inject a bit of a correction dose now.
Obviously if my BGL seemed like it would be too low (hypo) after 4 hours I would do different things…
5. Options if BGL looking low
If my BGL fell 4 mmol/L after 1.5 hours, I might take action to prevent a hypo:
Let’s say my BGL fell 4.7 mmol/L after 1.5 hours. Going down that same column, I might expect a full drop of 15 mmol/L, which is obviously too much if my starting BGL was 15 mmol/L.
Maybe I’ll check my BGL again before 2.5 hours (which would be a drop of a bit less than 10 mmol/L) and make sure I eat something sugary before then – enough to cover at least 5 mmol/L for me.
6. Options if BGL ‘on track’
Even if my BGL looks like it will drop by a good amount, I still find it useful to use the table for making a decision.
After 1.5 hours, perhaps my BGL has fallen 2.8 mmol/L, and after 4 hours, it fell 9 mmol/L (so I could go from 15 to 6 mmol/L – a nice number).
After 3 hours, I could have still done something like go for a walk or eat something or whatever – and I would’ve had good info about how much to eat or inject.
