My doc tells me 70 - 140 is good. Although since being on insulin I've gone as low as 46, felt the shakes, recognized that I was too low, and drank some OJ to bring me back up. You just need to be able to recognize from the way you're feeling if you're too low. If you don't feel any different when you're too low, then you might want to bug your doc.
Well as diamond said earlier, those are classic low blood sugar signals. One of the members made an interesting comment. He said that he got the shakes and the dizziness with any reading below 100. His Doc's explanation for this was that his body had been running on high sugars for so long that when he dipped below 100, it was simply reacting as if he was very low and that given time it would readjust. Makes a lot of sense to me. I think diamond put it very well when she said 70's were wonderful readings depending on when you were getting them!
I am an avandia and metformin user at pretty much the same levels you are but I take glucotrol instead of the amaryl. What happens is the Lantus gives you a good baseline level of insulin for a constant 24 hours and your amaryl like my glucotrol gives you a bump in this level when you take it. What my doc did was to give me the avandia in 2mg tablet so I could experiment with taking 2mg instead of 4mg to see if my sugars were avoiding the dips without creeping excessively high.(I can always add another 2mg pill if I've guessed wrong) The avandia is very powerful stuff, but its also the culprit behind water retention and weight gain, so I'd LOVE to be off it one of these days!
So, what happens is when you take your cocktail of Metformin, avandia, etc. you are bumping your insulin production AND bumping your sensitivity to it. One side of the equation could./should probably be reduced to help if you feel you are constantly to low (BUT I'd SETTLE FOR THOSE NUMBERS ANY DAY)!!
One last thought on your readings. As has been said before, a lot depends on when you take them. Try an experiment and take a reading every half hour after a major meal until you reach that low or get 4 hours out, whichever comes first. This will show you what is happening with your BS after a meal and how your body is handling the meal. If you don't spike badly and you return to the 70's in short order, well you're doing something right and you probably could even with a doc's permission cut back on your lantus a tiny bit.
So most importantly, find out where your BS is going when you aren't watching it, like after a meal !!
Hope this helps
I get the dizziness and shakes in the high 60's so maybe low 70's is to low for you!