Basal-bolus / insulin-resistance questions

[rhu]

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[LittleSue]

If I understand it correctly, the idea being that the basal injection is a type of slow-release ('cloudy') insulin taken once a day to keep a check on background sugar levels, whereas the bolus is a rapid-release ('clear') insulin for mealtimes. The purpose of such a basal-bolus insulin therapy for people with diabetes is to copy the body's normal production of insulin as closely as possible.

What determines whether human (non-diabetic) insulin is fast- or slow-acting ? Are there different chemical compositions (what's the difference between cloudy & clear?) or is it purely down to the concentration of insulin dumped into your bloodstream at any given point in time?

Hello

Your understanding of basal-bolus is correct. (Modern long-acting analogues Levemir and Glargine are clear, and may be taken twice daily, but traditionally the longer-acting types were cloudy.) Hence if your basal dose is correct but you don't eat, in theory there's no need for bolus. This is the basis of DAFNE - get the basal right and if/when/how many carbs are eaten is your choice, just bolus when needed.

I think the insulin non-diabetics produce is all fast-acting.

Non-diabetics produce a background amount of insulin all the time, but when they eat carbs they automatically produce extra to keep BS in the normal range. Basal injected insulin has comparatively consistent action and can't cope with ingestion of carbs. Type 1s can't produce a bolus naturally, hence they inject a bolus to cover the food eaten. Those using a pump continually pump fast-acting insulin and set the pump to give a bolus when they eat, or to reduce the rate when exercising, which is perhaps the closest we have to what non-diabetics take for granted.

You could think of it like a car with cruise control, where you can set the throttle pressure, take your foot off the pedal and car keeps going at the same throttle setting:
-Cruise control (or keeping foot on throttle at same pressure all the time) is like basal insulin. On level road [not eating or exercising] it keeps the status quo.
-When you need to climb a hill [eat carbs] more throttle is needed [more insulin to cope with the carbs].
-Whereas an experienced human driver would adjust throttle pressure virtually automatically, cruise control can't do this. Likewise a type 1 can't automatically produce extra insulin when needed, so has to do it manually by injecting bolus.
-If you rely solely on cruise control [basal insulin] the car would not have enough power to climb a hill [not enough insulin to bring down bs after eating carbs] so you'd have to increase throttle pressure manually [bolus] to cope with the extra demands of the incline [or food] and then ease off when the road levels out [short acting insulin designed to stop working when carbs dealt with].

Hope that analogy helps and didn't just confuse you!

Sorry can't answer your other questions, perhaps the professionals can.

Sue