July 2, 2004
Pills for Diabetes, Type 2
Question from Bedford, IN, USA:
My husband’s two hour postprandial readings are in the 75 to 100 mg/dl [4.2 to 5.6 mmol/L] range, which is fine. However, his fasting level is usually in the 100 to 125 [5.6 to 6.9 mmol/L] range. His doctor wants him to start taking 500 mg of metformin twice a day, again. When he was on it earlier, his fasting levels were no lower than they are now. So, with that in mind, can you help me understand the benefit of metformin in reducing liver output when his fasting levels, although higher than normal, are not what we been told are dangerous?
The following question was put to our doctor who couldn’t explain where my thinking was wrong, but she couldn’t explain why the liver suppression was such a good idea. Since she’s not an endocrinologist, I thought maybe your team could help me understand. The liver puts out glucose from stored fat when it gets a signal that cells are running low on glucose. Now, this doesn’t always correspond to circulating levels of glucose in your blood. This means that even though your blood sugars levels are fine (or even high), your liver gets told to dump some out because that glucose already circulating has not gone to the cells to do any good. This is either from being insulin resistant or from low levels of insulin in non-insulin producing type 1s or progressed type 2s.
Now, based on that premise (which could be wrong, and if it is, I want to know) if the liver output is suppressed, your body will not get the glucose it needs to function properly. When this happens, the body starts eating itself (muscle tissue, etc.) to make up for the lack of fuel. Then, the kidneys are forced to work overtime to deal with the bad leftovers that eating your own muscles put out. So, if his liver is suppressed, his cells don’t receive fuel, his muscles get eaten up and his kidneys get damaged. Doesn’t sound good, does it? I know if his blood sugar levels were extremely high, I could see the benefit. But at his current levels, isn’t that trading one problem for another problem that could be worse than the first one?
Answer:
I think you deserve merit pay for trying to get to the bottom of this. However, one of your premises is not quite correct. The situation in diabetes is that liver glucose output is elevated above normal, but it is not zero when suppressed down to normal. That means, when it is well treated, the cells of the body are not deprived of adequate glucose. To answer the clinical problem, I think your physician is treating your husband appropriately. It may take time, perhaps months, to get the fasting glucose down with the addition of the metformin. Fasting glucose levels are normally less than 120 mg/dl [6.7 mmol/L]. Make sure the A1c is normal. That is most critical. Metformin does not usually cause hypoglycemia, so the down side (assuming no complications) is not great.
JTL
