Same as what everyone said above. I'm really sorry you're going through this, it is such a sad time and such a hard decision. I'm sure you will do whatever is best for Loki, if necessary.
I can tell you what happened with me and Brownie...Brownie had cancer and ended up with a tumor in his spleen that made him sick. He would go out the door, then just stand there, or lay down. He also quit eating. When the vet told me about the tumor, she said it could burst and be very painful for him, so that is what I based my decision on. I didn't want him to go through something like that, especially when I was away at work or something. Anyhow, I made the decision, and I had my sister come over, for support. She knew Brownie very, very well, and one thing she said was that she noticed he was "checking in and out" if you know what I mean. It was like he went into a place to zone out from the pain/illness/feeling bad, then he would begin to move around a bit and interact with us. He always stayed physically with/near us, but his mind was sometimes busy coping. It's a subtle thing. I guess it's one aspect of "quality of life?" Not sure if this is helpful, but sometimes hearing other people's experiences helps, so I wanted to share.
Keep us posted on how Loki is doing.
- A-Jay (APBT)
- Remy (English Setter mix)