Background Insulin

Hi James,

I don't know where that formula comes from, but I'd be extremely sceptical about it. For one thing, it tells me that 1 unit of bolus covers 23g carbs, which is waaaaay wide of the mark. For another, it takes no account of diet, exercise, weight, insulin resistance, or any of the myriad other factors which can influence things.
The most reliable method of establishing the right basal level is to fast for 24 hours and find the dose that keeps your bg on an even keel throughout that time. No, I've never done it either! Like the vast majority of people, I worked my doses out by trial and error.

All the best,

fergus

James

I know exactly what you're after, but I think fergus is right on the basal testing. Another method which doesn't involve a 24 hour fast, is to spread the test over 3 days and they don't have to be consecutive. So on day 1 you skip breakfast and test every 2 hours (starting at 2am) until lunch, day 2 you skip lunch with 2 hourly testing instead, day 3 you have a very late supper having eaten nothing since lunch. This is how I do it but I'm on a pump so this may be why it works for me.

The 500 rule you mention is quite common, but not completely accurate and does rely on your basal being around 50% of TDD. In addition, your insulin/carb ratio will vary over a 24 hour period, I use 3 starting at 1:10 in the morning, 1:12 in the afternoon and 1:14 in the evening. I use the 500 rule as a guide or starting point only which you then have to fine tune with trial, error and a fair bit of testing.

The 100 rule accompanies this and is used to work out your correction ratio - 100 divided by TDD gives you the number of mmol/l your bg will reduce by with 1 unit of rapid acting insulin. Again it relies on your basal being around 50% of TDD but I actually find this rule more accurate and less prone to variation.

For both of these calculations I never rely on 1 day's worth of data but use a weekly average instead. They're useful checkpoints though and definitely worth the effort!

I agree that the only real way to find out is by basal testing and I do it in segments rather than fast for a whole day.
This document gives formulas for insulin initiation including the 500 rule and the rule for correction that kegstore mentioned... however it is in mg/dl so it's the 1800 rule .
It uses weight as the basis for initial basal dose. I think they used this formula when I was diagnosed but it was a couple of units too high once I left hospital and became active again. (and now on a pump I use far less basal than the formula would suggest )
The 500 rule doesn't work out for me either resulting in too low an insulin to carb ratio. ( my basal is about 42% of TDD rather than 50% )

So all in all, heres some formulas, but they don't really work for me.
.http://np.ce-today.com/resources/diabetes/InitiatingInsulinTherapy.pdf

Agree with all advice on testing and also on the rules

I moved from mixed to basal/bolus and based on Total Daily Dose and weight neither rule works for me AT ALL

Also, they rely to a degree on you knowing your total daily dose, which kind of defeats the point to me! DNS dont use that rule I dont think, though John Walsh and Gary Shchneider, who have both written books on insulin do use the rule

I also find their correction bolus rule also completely bonkers wrong! For me
For you it might be spot on - and therein lies the diabetic dilemma. Whats sauce for the goose etc

This sounds really silly... but what exactly should I be looking for when fasting to test by background insulin? If I start at 7.5 should I be sticking at exactly 7.5 all day, or is fluctuations between 6.5 and 8.5 ok?

Last week I went progressively down from 15 to 7 and then started rising again back up to 12, over 12 hours.
Yesterday I went progressively down from 22 (probably a somogyi?) to 6 over 12 hours, but hovered happily at 10 for a couple hours in the middle. [to be even more confusing I then ate tea, and went from 11 down to 4 overnight despite a 1.5CP snack at 4am when blood was 6]

I know both of those background doses clearly aren't right... but I just wondered quite how 'perfect' we can expect to be and therefore what is a realistic goal to aim for and what is totally unrealistic and never achievable. My Dr wants me to stick as close as I can to 20 units of BI but I think it needs to be significantly reduced if either of the fasting days are anything to go by.