Here's a great article that I found on some of the top Health issues specifically for Dachshunds.
My two little girls were supposedly "Minis", though they couldn't guarantee that they'd be Mini's. And since they're both over 11lbs, they certainly not. But they are "Tweenies" -- at a whopping 14-15lbs.
We have really tried to reduce their weight. We walk the dogs regularly and also feed them less food. We now give them 1/3 c of food each in the morning and evening. I was told that that wasn't too much. But when we give them less, they are still wandering the house and yard looking for anything to eat!
I've heard of course about the issues with the back, so we are trying to be as cautious and healthy for them as possible.
They are totally our little children. :)