Glucose levels dropping fast

I'm on my 6-month supervised pre-op diet for RNY.  It's very strict, with 2 high-protein shakes and one low-fat meal a day.  And tons of vitamins.  I've only been on it since 9/29.  Normally my fasting reading is in the 80s-90s.  The first morning I checked it, my fasting reading was 56.  And my post-evening-meal reading was 89.  I've had to completely cut my fast-acting insulin, and my long-acting went from 72 units to 45.  Has anyone else experienced this?          

This is typical and expected - and probably has to do with the cut in your carb intake - fat intake does not increase BG, or only very slightly). I have to say, the diet sounds incredibly stringent for a full six months. When I did my last-ditch effort diet before WLS, I did 8 months of a very low carb (30 grams a day - Dr Bernstein), low-calorie regimen, and cut my insulin dosage by 80% and normalized my BG within about three weeks.

If you are experiencing evening post-meal readings that low and hypoglycemic fasting sugars, you may need to cut your long-acting even more, because you may actually be experiencing severe hypoglycemia in your sleep. When you are making radical changes like this, it is a good idea, if you can manage it, to test VERY often for a week or two, including setting your alarm to check during the night, so that you can judge how each meal affects your BG and fine-tune your insulin doses in response.  I did this - testing fasting, before each meal, two hours after each meal, and once during the night for a week, kept careful records, and was in that way able to adjust the dosages to maintain normal BG without hypoglycemic episodes. Thankfully, I no longer have to take insulin at all. 

Good luck!

I agree with Ros-mari that that sounds very strict for 6 months! For my 6 months, I am limiting carbs (my doc said to try to keep it under 150g per day, but I find more success at leveling out my glucose readings if I keep it closer to 50g per day) and tracking calories, trying to stay below 2000.

Anyway, yes, with cutting the carbs, my glucose levels are in MUCH better control. I am not on insulin, though, so my numbers have not been as low as yours. I also agree with Ros-mari, though, that you should test quite frequently. The only way to get a true picture of how your body is handling everything is to check your fasting, pre-meal, AND post-prandial numbers.

heh, my doc gave me a prescription for my test strips and said it was a 3-month supply. I needed more in about half that time

Oh yes I went through that when I started to lose some weight.  I hated hated hated the hypoglycemia.  I know I'll be going through it again when I get surgery and mildly dread it.

Thanks to eveyrone for your replies.  Yes, I have been testing more frequently during the day, although I have not done it overnight.  So far since cutting back the long-acting insulin to 45 I seem to be stabilized.  I'm so glad to be down to one insulin, one shot with my pen, so it's very easy.  I suspect that as I lose weight, I'll be able to cut it completely, as I've been able to do in the past. 

Once again, thanks everyone!