Dan Evans' Excel spreadsheet for insulin calculation
Download
the spreadsheet (1.6Mb Excel 2000 file)
(Probably easiest to download by
right clicking, then "save target as..")
Who is this information for?
Diabetics on insulin who wish to plan their insulin doses. In particular,
it is most suited to those planning twice-daily (before breakfast / before
dinner) injections mixing multiple types of insulin - but it should be
useful for those on insulin pens too.
Note that this web page / spreadsheet is provided for information only,
and should be used in consultation with your healthcare professionals: I
take no responsibility for your use of this information.
What is it?
Various different types of insulin are
available. Each of these has a different "time-profile" - effect
over time. Short-acting insulins (eg NovoRapid) have short lasting effects
(maybe 2 hours); longer-acting cloudy insulins (Humulin I etc) are
available which can last 24 hours or more.
The twice-daily syringe-given mixes of different insulins has gone out of
fashion a bit (in favour of 4 or 5 times daily pen injections). However,
if you are still on twice-daily syringe-given mixes of insulin (or
considering changing to them), it's important to know what combined effect
the insulin you are injecting is having over time.
My spreadsheet lets you combine different amounts of different insulins at
different insulins, and see the effect of the insulin over time, in graph
form.
More details
Load up the spreadsheet (downloadable above) to follow the below! It does assume a moderate knowledge of Excel to be able to use it!
Insulin manufacturers publish
time-effect graphs for their insulins. I started by going to insulin
manufacturer websites and getting these time-effect
graphs. I displayed them with grid lines, breaking them down
into 30 minute blocks. I put the 30 minute values into Excel, and normalised
to 1. The results are in the "Time_profiles" sheet:
these should not be changed. [At a later date, up to 4 more insulin
types could be added to the time profile chart if required]
An important point to note is that the names of the insulins are those
available in the UK. Some names differ in other parts of the world. The
equivalent UK-US names of Lilly insulins are:
UK Lilly Humulin S = USA Lilly Humulin R
UK Lilly Humulin I = USA Lilly Humulin N
UK Lilly Humulin Lente = USA Lilly
Humulin L
UK Lilly Humulin Zn = USA Lilly
Humulin U
UK Lilly Humalog Mix25 = USA Lilly Humalog Mix75/25
UK Lilly Humulin M3 = USA Lilly Humulin 70/30
UK Lilly Humulin M5 = USA Lilly Humulin 50/50
I'm not sure about the Novo insulins.
You can see a comparison plot of each of the insulin types in sheet "Time_profile_chart". I've actually used two different y axes, since the shorter acting ones obviously have higher peaks, so I put those on a different scale.
The main part of the spreadsheet
(where you enter insulin taken and BG info) is the
"Log_sheet" sheet. This is done in 30
minute chunks. It currently contains some typical insulin doses that you
might be taking - namely:
AM (8:30am): 6 Novorapid + 35 Humulin I
PM (8:30pm): 5 Novorapid + 10 Ultratard
You can obviously delete these values and put in your own values.
A key feature is the pull-down boxes at the top. It
allows for 3 different insulin types to be used. The name of the
insulin selected in the pull-down box for a column tells you what that
column represents. So if "Novo - Actrapid" was selected in one
of the pull-downs, and a 5 was entered somewhere in
that column, this would mean 5 units of Actrapid
were injected at that time.
[If you temporarily want a certain column ignored /
not taken account of in graphs/totals etc, then
select "Ignore this column" from the pull-down]
By using the time-effect information (mentioned above) the spreadsheet works out the equivalent amount of insulin delivered in each half-hour period, as a result of each of the 3 different insulin types. And yes - this does take account of "yesterday's dose" too (or any other earlier dose, for that matter). The total equivalent amount (as a result of all 3 insulin types) in the 30 minute period is also then calculated.
Please don't change the "Insulin_names_for_pulldown" sheet - this is for internal spreadsheet use only.
The "Insulin_Effect_Chart"
plots the values - showing BG points, and lines for
total insulin and each of the three types. The example plot below shows
NovoRapid (brown), Humulin I (yellow), Ultratard (blue) and total insulin
(purple) [in the spreadsheet itself, there is a key on the left hand
side]. Time runs along the bottom.
The system allows you to go and select different insulin types from the pull-down lists (in the "Log_sheet" sheet), and/or put in different doses, and see a revised insulin effect chart. The chart should update automatically when you change a pull-down. If this doesn't seem to be happening, either press F9 or save the spreadsheet, close it and open it again: then you'll see the revised values charted.
Assumptions made
Assumptions made are:
- increasing the amount of a certain insulin increases its intensity, but not its length / time profile.
- chemicals in one type of insulin do not effect the other type of insulin, when they have been mixed. I know manufacturers tend to be cagey about mixing insulins, but I've had good experiences in the past. (Although I know that it's dangerous to mix Lantus with other insulins).
Using the spreadsheet
The best way to make use of the spreadsheet is to note down your current
blood glucose problems (eg too high at 2pm), then look at the "Time_profile_chart"
to choose an insulin type that might solve the problem. Then select it in
one of the pull-down lists (in the "Log_sheet" sheet)
and put in typical doses. See the combined insulin effect in the "Insulin_Effect_Chart"
chart & use it to check if you have too much / little insulin at
different times of day.
I hope you find it useful!
--Dan Evans. May 2003.
dan at danevans.co.uk