I guess maybe I'm posting this for people who've had similar experiences for any advice. Maybe I'm just posting it to relieve some tension.
I've had a frustrating and depressing last few months with my dog. I have a sheltie, Eddie, who is 11. He's gone from over 40lbs last year down to 23 and is just skin and bones. He simply doesn't eat anymore unless it's some kind of treat. (doritos or pizza crust for example) We've tried every kind of dog food - dry, canned, everything in between.
He's also gone completely blind and gets lost frequently going outside - so much that we have to run outside and grab him before he REALLY gets lost. Let me tell you, in Nebraska in winter, it is no fun running outside in slippers through a field to get your dog.
He's at the vet every month and had lots of tests that all come back ok. The vet thinks he most likely has some sort of cancer that we couldn't do anything about at this point anyway.
But he's still HAPPY. He's not having accidents in the house or anything like that. He did fall down the stairs yesterday because he forgot they were there. I just don't know at what point should be the end? I mean, I hate to let him get down to 10lbs. But if he's seemingly happy, is it fair to put him down?
I know the feeling that you have and it put a pit in my stomach for you.
Anytime I had to deal with this in my life, somehow the dog let me "know" it was time. It's so hard when they look so normal and happy on the outside but so much is going on in the insides.
I don't have advice as far as "when" it is time for your babydog. Give him lots of hugs and kisses, knowing he had the best life with you and knowing how much you loved each other.
I don't know why dogs can't live our whole life span with us, they are amazing animals.
I work at a vet and I get asked this question every day. I watch people struggle with it. I'm going to tell you the best advice I ever heard and the advise I hold true with my own pets, particularly my 13 year old dog with dementia.
What three things are your dog's favorite things to do? Think of those three things and when he no longer enjoys any of those things, it's time. My dog has to wear a diaper in the house. He gets lost in the yard. He receives injections for his arthritis. He gets scared by lots of noises and spends most of his time sleeping. But he is happy, he is as healthy as he can be, when I look in his eyes it's him looking back at me and not pain. So it's not his time. I know it's getting close and I am going to lose my mind afterwards, but I'm going to be strong for him until the very end.
If you're going to the vet regularly and his tests are okay, that's a good sign. If the vet hasn't taken you aside and told you s/he thinks it's time, that's a good sign. Make your home as well-adjusted as it can be for him - I would put up a baby gate to keep him away from stairs or rooms he shouldn't go in because you don't want to risk an injury to a frail, underweight dog. Try to feed him as well as you can but know if, unfortunately, he's not eating the correct measurement for his weight, he isn't going to gain and he is probably going to continue to lose.
Ultimately, this isn't going to be an easy decision no matter what anyone tells you. It's going to be really, really incredibly hard. But listen to your heart - when you're hanging on to him for YOU and not for HIM, your heart will tell you to let go.
My heart goes out to you, I have been in your situation. This was truly the most difficult decision I ever had to make, but one that had to be made. I will warn you, you will not feel better afterwards just be comforted that you made the best decision you could and remember that you gave him a loving, happy life.
I agree with PUPMOM's idea. Honestly, we knew it was time when our pets (the two that had to be put down) were in too much pain. One of them was mostly blind and partially deaf and liked to cuddle close to people because that was really the only time she could see and hear them and warm up... but when she developed an abscessed tooth that couldn't be fixed without a surgery that she likely wouldn't live through, it was time. The other had seizures that were increasing in frequency and severity until one day, she couldn't walk anymore and had trouble breathing. It was time.
It's so hard to let go, but when it's time, it just can't wait. I believe they know, though, that we're just trying to help them and we're doing it out of our love for them. That doesn't make the decision to euthanize easy though.
Im sorry your going through that. I can't really give you much advice. I know with our family dog we got him after my dads massive heartattack. They were very close, he is 17 years old right now, this last year was hard on both him and my dad. He was there with my dad through out his time on hospice, he would lay with my dad, my dad passed away in November a few days before he passed away he asked the dog if he was ready to go home. Our dog is still hanging in there I don't know whether he knows he brings comfort to mom and the rest of us, but he is going blind, deaf and it is hard for him to get around. We do know he is not in any real pain tho. So we are going to leave it up to him, like we did with dad. And when it is his time we know he will go and be with dad.
Every dog is different I think if your dog isn't in any pain, then give her lots of hugs and love and let them choose when they leave us.
I appreciate the responses, I really do. The "three things" idea seems to sound like something I could appreciate.
Really, the only thing he can't do with us anymore is "herd" us as he can't see us, so that must be frustrating for him - having a flock he can't really tend. Otherwise he seems to be able to do everything else.
I suppose that really is true, that you just "know" when. I worked with animals in my prior life before my current career and found that to be the case most of the time.
I'm going through a similar situation with my dog. It's time for him to be at peace, I'm just not emotionally ready. But he is showing all the signs that he is ready to let go of the pain he's in. The decision will be made very, very soon.
Hugs to you
I'm sorry for you too, Mozzy. It's one of the most heart-wretching decisions we ever make but I wouldn't trade the time with my doggies for anything in the world.
I grew up in a vet clinic, I saw this struggle a lot. There's a lot of good advice in the responses here.
One thing I would stress is don't let him go too far downhill. Euthanasia when there is still a little quality of life is far kinder than waiting & letting them suffer
This for sure is one of the hardest experiences but you just have to choose what is right for your dog. Glad he is not in pain but wasting away could be a sign of something terrible going inside his body. I still believe you are the best judge........but my suggestion is don't let him suffer, set him free.
I'm entering the same place with my 14yr old Golden Retriever mix. I know I'll have to make a decision at some point this year.
I read The Art of Racing in the Rain by Garth Stein a few years ago and remember thinking I would have to reread it again when the time came to make a decision about euthanasia. While it was an emotional read, it touched humanely on this very decision.
I'm so sorry you are watching your beloved pup get old before your very eyes. It is incredibly hard to let go.
As far as when, I agree with the advice you have been given. I know with my Roman, he just looked at me one day and I could see it in his eyes that he was ready. At that point I could not be selfish and make him "hold on" longer for me.
Just give him lots of love and hugs. Oh, and I plan on getting my Libby's paw prints stamped to save. (I am going to have that turned into a tattoo on my wrist.) She is getting up there in age and I worry about coming to that bridge.
Hugs, and so sorry you are struggling with such an emotional decision.
There's nothing harder, in my opinion, than making the decision of when to "let go" of your beloved pet.
I've had to do it a few times, but none so difficult as with my Trixee, last February. She was like you described... fur & bones, would hardly eat, but still peeing & pooping & basically doing OK. And like your dog, Trixee fell down the stairs... more than once... scared me to death & even tho she suffered no physical injuries from it, you could tell it scared her too.
I've always believed that if your pet is sleeping/eating/drinking and peeing & pooping pretty much in a normal fashion, then by all means, let them live as long as they can. But once any one of those things becomes an issue - a REAL issue - then it's time to let go. Trixee was eating & drinking right up to the last minute. But the deciding factor was when she needed to go pee, and she collapsed on the floor - all four legs just seemed to give way. I knew it was time, then. And it nearly killed me... but I did it... FOR HER.
Good luck with your decision, I know it's not an easy one by any means. Blessings & peace to you & your pet.
I'm going through the same thing right now...so I can understand.My 13 year old is going blind,he's already mostly deaf,and he's lost enough weight that everyone keeps asking me when I'm going to put him down.He's healthy enough that the vet keeps telling me it's not time yet,and that I will know when it is.It's not easy and I can't give any advice...but just know that you're not alone
When is it time to let your dog go?
It's never easy to make that choice. 
