Hello, my name is***** and I have over 20 years of experience as a veterinarian. I'm sorry to hear that your girl isn't feeling well and is eating poorly and has lost a significant amount of weight.A decrease in appetite can be related to eating something she should not have, too many treats or table food
, eating foreign material (which could cause a full or partial gastrointestinal obstruction), chronic pancreatitis, esophageal reflux, a dietary allergy or sensitivity, toxin exposure, a viral or bacterial infection, inflammatory bowel disease, heartworm
(a tumor of the thyroid gland) internal organ failure, or even infiltrative cancers such as lymphoma.Because she hasn't eaten normally in several days and she is obviously losing weight I am very concerned about her. I understand that she is drinking but if she isn't drinking enough she will quickly become dehydrated, especially because she isn't eating and cats take in fluids through their food as well. As she is losing weight and her liver breaks down fats for energy to live she may develop a type of liver disease called hepatic lipidosis. This is where the liver becomes overwhelmed metabolizing fats to support the body's energy needs and cannot perform other essential functions.Ideally she would see a veterinarian today since this has been going on for more than 72 hours. Simple stomach upset should pass within 24 to 48 hours. They could examine her, run blood tests and possibly check radiographs and/or an ultrasound to evaluate her and know best how to treat her.In the meantime they can administer injectable anti-nausea drugs and fluids to rehydrate her as well as an appetite stimulant. If finances are limited you can ask if the laboratory they use offers a mini senior health panel which while not as detailed, should hit most of the metabolic enzyme levels they need to see for at least a tentative diagnosis. You can also ask that diagnostics be done in a stepwise fashion so that you can pick which ones to run depending upon the blood test results. If you cannot have her seen for whatever reason there are some things you can try at home, but when cats don't eat for a long enough period to obviously lose weight that are rarely enough.At home to try and settle her stomach you can give either:1) Pepcid ac (famotidine) at ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 12 hoursOR2) Prilosec (omeprazole) at ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 24 hoursThese are acid reducers and may help her feel less nauseous so that she will eat. They are quite safe and can be used long term if necessary.You can use a medicine syringe to try and force water into her orally.A couple of hours after giving the acid reducer I recommend offering meat baby foods or a bland diet of 2/3 boiled minced white skinless chicken and 1/3 boiled white rice mixed with some low salt chicken broth to make it more palatable, get fluids into her, and make it easy to lap up and swallow.If she continues to not eat she should see her veterinarian for an examination, diagnostics and intravenous fluids and supportive care.Please let me know if you have any further questions.