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I have Type 2 diabetes, but I take insulin. My question is: does injected insulin replace or supplement native insulin?

The reason I ask is that I take small amounts of insulin (4 units of R at breakfast, 6R at lunch, 8R at dinner and 14N at bed), and am able to maintain a normal A1c, but if I don't take insulin, my BGs start to go up. I'm wondering if there's any way of knowing (short of an expensive test) whether I'm insulin-deficient or resistant.


To answer your question fully it would have helped to have had a little more in the way of history: your age, body weight, age of onset, family history and any previous use of oral hypoglycemics, etc. It is possible for example, that you are actually a Type 1 diabetic even though you are an adult: onset as late as the fourth decade has been described.

You could probably establish this by asking your endocrinologist to get antibody tests done. In this case your pancreas may still be producing some insulin which accounts for your low dose; and the dose you inject is "supplementing" your own insulin. Later on, injected insulin will probably be your only source of the hormone and then could be regarded as a "replacement;" there is no resistance.

If, on the other hand, you are indeed a Type 2 diabetic, you are likely to be insulin resistant, and not producing enough of your own insulin to meet your extra needs. The dose you take in this instance would be a "supplement," although in time your own ability to make insulin could get exhausted, in which case the injected insulin again becomes a "replacement." There are several ways to test for resistance, one being to get a serum C peptide level (C peptide being the residue left when the insulin precursor is made into insulin). There are many other reasons for insulin resistance, but your low dose makes it exceedingly improbable that they are a factor in your instance. In any case, this distinction between "supplement" and "replacement" and "resistance" and "deficiency" is not really important (practically) for you. So I would stop worrying about expensive tests and concentrate on keeping that A1c at its present low level.

It sounds as though you are doing very well. Good luck!


Original posting 31 Aug 96


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Last Updated: Tuesday April 06, 2010 15:08:52
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