I have a 13 year old lad. She lost her best buddy Teddie a 16 year old terrier this past June. We had just moved to a new house in April and I got a full time job, so she's been alone all day without her buddy and me and she got very depressed. I would walk her every nite for at lleast an hour. She was 56 lbs then and now she is down to 40. We took her to the vet and they did exrays,ekg, blood work and found that her heart was enlarged but not to much, her blood counts were good, but her kidneys were a little out of whack, they had put her on antibiotics and predisone in October because she wasn't eating very well and she was gagging not alot but enough to worry me. Then when I took her back in Dec that's when they did all those tests she had lost another 2 lbs. Now she is on heart pills, predison and stronger antibiotics but she refuses to eat and I'm afraid she will strave herself to death. Also with all those pills and no food what effect that will have on her stomach. I put some of her dog food and carrots and carrot juice in a blender and feed it to her with a dropper. Any suggestions I'm really worried about her not eating

Oh, Darling, I'm so sorry!
You can try feeding wet food, maybe with puppy formula mixed in, and talk to the vet about supplements, or even check with a different vet to learn about options about which your current vet may be unaware but I'm very much afraid that the chances are that your time with your friend is growing short.The typical life span for Labrador Retrievers is 10-13 years, and as you already know, they are extremely social and suffer badly from the loss of a familiar companion.
I am so sorry to be so pessimestic, and hope I'm wrong, but just in case I'm correct, please do your best to make the most of the time you have left with your friend.

You have my heartfelt sympathy. As one pet mommy to another, I know how helpless it can feel to not know what to do for our babies.

I'm sorry about your lab. I lost mine a couple of months ago...he too was losing a lot of weight. Like MsS said I would also consider a second opinion from another vet. In the meantime you could ask your vet about a prescription diet called A/D it is given to pets that don't want to eat or are pregnant. You could also try baby food and maybe some turkey or roast beef. My vet at one point also had me feeding my dog spaghetti which did help him gain a little weight.
Good Luck with your dog and please keep us posted.