My Cat Won't Eat Or Drink And Is Losing Weight, Can You Help?

There are many things that cause weight loss, anorexia, and lack of thirst--these are very vague signs.  This cat needs to be examined by a veterinarian.  Screening blood work needs to be performed.  This will check for kidney disease, liver disease, hyperthyroidism, diabetes, assess red blood cells, white blood cells, and platelets.  Another concern would be for neoplasia of infectious disease.  If needed imaging studies may be done--x-rays or ultrasound.  
At this point your cat needs symptomatic care as well.  It is dehydrated and in a negative calorie balance.  Treatment will include fluid therapy and nutritional support.  Cats can develop a secondary condition from not eating--it is called hepatic lipidosis (fatty liver disease).  It is important to determine the cause of your cat's illness before this condition sets in.