How old is your cat? Is he eating normally? Is he using the litter box? What are you feeding him? There are many causes for weight loss, from age to improper diet, to parasites or cancer. If you could provide more information I'd really appreciate it. If not, then my best advice is to do the obvious.
The cat is about 10 years old. And no he isn't eating at all. When I noticed he was losing weight I started feeding him more and he seemed to be eatting. But now he wont eat at all. He does drink a lot of water. We feed him Chicken soup for the cat lover's soul for adult cats.
Get a syringe or eye dropper and force feed him. He might be dehydrated as well, so he needs liquids or you will have to take him to the Evet for IVs. A cat 10 years old is considered senior but he isn't too old to give up on him. You need to get him tested for FIP and other illnesses that may be causing this weight loss and lack of appetite. I am pretty sure there are appetite stimulants over the counter for cats, but I'm not sure if they work. I would hate to give tell you to spend money on something which is far from being beneficial.
I am suspecting your cat has one of the following: Cardiomyopathy (because he is eating less), diabetes, kidney failure, cancer, feline leukemia, feline immunodeficiency virus, feline infectious peritonitis, other systemic illness.
We are talking about tests which need to be done to reach a diagnosis and treat him accordingly. Other than force feed him and maybe try appetite stimulants, your kitty will not stand a chance if you don't get him treated; that means he needs to go to the vet ASAP. Weight loss is never good, and there is usually something very, very wrong and powerful hidden behind the effects.
I know you don't want to read that you have to take him to the vet, but look, your kitty is very ill, and it isn't kind to have him suffering. It is only fair to give him a chance. You will never know what's wrong with him until the vet gives you the answer, and you deserve to know what's happening to your cat. I'm sure you agree with me. Take care, and keep us posted. I'll keep my fingers crossed all the time so he gets better.
Let's see a 10 yr old cat that's losing weight and losing hair. This, to me, sounds like your cat has an overactive thyroid. Try doing a google search or yahoo search on hyperthyroidism and see if the symptoms fit.
There's also a possiblility of kidney disease, as well. That could cause weight loss, too, but not hair loss.
My main suspicion is hyperthyroid disease. This can be extremely dangerous because the heart rate increases big time. This can cause heart failure. This condition can be controlled with pills.
I've had hyperthyroid cats, but they haven't been so bad that they've lost hair. Your cat is in serious danger. You will be able to tell if his/her heart is overly stressed because you'll see the cat panting and getting tired very easily.
If vet bills are a problem, then visit this forum's health pages located under Health Pages-it's on this page at the top right of the screen above Recent Activity.
Do Not Delay.
Good advice. All I have to add is just that there is a health pages article about force feeding/ syringe feeding that may be helpful for you.
In addition to going to the vet as soon as possible, it is very important that your cat gets sufficient hydration and nutrition. Even a healthy cat can't go very long without it.
Good luck. Keep us posted.