My 11 year old golden retriever has suddenly become lethargic, unwilling to eat, and won't pick up her head.

Don't take any advice from here. Take your dog to the Vet's Office

Well there's really no way anybody could give you a diagnosis with so few details and of course you should never get a diagnosis on the net.The only way to be a 100% sure of what the problem is is to get her examined by a vet.

Because of her age and breed there could be a lot of age related problems.11 years for a large breed dog is old.So there could be kidney,liver,heart failure.If she haven't had the vaccinations she needs it could be an infectious disease like hepatitis,Carre etc.It could be an infection of the blood like leishmania,ehrlichia etc.It could also be a normal infection/irritation of the intestinal tract.

The sudden appearance of the symptoms tell us it is probably an acute problem(not something she's been having for years,like kidney or liver or heart problems).Of course there could be minor symptoms which you missed.

Get your dog to a vet as soon as possible,that's the only way to find out what is wrong with her.Being lethargic though and refusing to stand are serious symptoms and a situation like this shouldn't be taken lightly.....go to a vet,it can get worse in just a few hours.The sooner you take her the more chances you have for a speedy and successful treatment.

Know where you are at my friend. I have a couple of old boys here, and while some of these things are just normal for their age, I never take the chance. Let the vet decide if there is anything to be conserned about or not.

I would take her to a vet, best to have her checked out early as it maybe an infection in which case a blood test can identify it. She is getting on a bit in years and this would be a concern. My advice don't muck around best to take her to your vet as you wouldn't want her to get any worse. It is most important that she does not dehydrate if she won't drink get a large syringe (10ml) and feed water into her mouth from the side. I hope this helps and she recovers.

VET NOW

Goldens have a very high rate of cancer and can be zipping along and suddenly crash and simply refuse to get up or eat.

There are many illnesses but without things like a temp (themometer needed) it is hard to say if is an infection

Mine started to act the same way so a trip to the vet and a couple of tests later the culprit turned out to be Lyme's disease. Luckily they now have medicine to counteract this, but sadly any nerve damage that has occurred is irreparable. My advice, get to your vet and have the test done as soon as possible for your both of your sakes. Good luck.

I would seek immediate vet care due to her advanced age and the sudden onset of the symptoms. There could be a number of causes but her kidneys would be at the top of the list. If she has been coughing she could have congested heart failure which causes fluid build up on the heart and will need to be treated with meds.

Get to a vet immediately! This is a sign of something very serious...it could be a number of things, but if you leave the dog untreated you will likely lose her.

Like the others said, take it to a Vet.

I would recommend you take her to your vet or a 24 hr vet hospital. Good Luck to your doggy and you.