People ask Dr Google for the “reasons why my cat is throwing up”. Here is an overview of the reasons but it is not a substitute for taking your cat to a genuine doctor; a good veterinarian if needs must. In fact it is a huge subject because there are many causes. Vomiting is a common cat health problem symptom like lethargy and loss of appetite. Self-diagnosis is hard and problematic. In all but straightforward cases a vet should be consulted.
Throws up once or twice, cat healthy and normal before and after
The vomiting is probably not serious. Cats are good vomiters and it is not unusual.
Throws up without eating
If the cause of the vomiting is not food related it is a possible sign of an infectious disease or disorder.
Diseases associated with vomiting
Kidney or liver disease and urethral obstruction. Central nervous system disorder, feline panleukopenia, tonsillitis, sore throat, inflammatory bowel disease (IBD), infected uterus, enteritis, gastritis. Young cats: panleukopenia. Peritonitis.
Most common reasons
Swallowing something indigestible. This might be hair or grass. Cats swallow their own hair and they eat grass for folic acid. We have all seen this. Indigestible substances irritate the stomach. Overeating or eating too fast is also common. Kittens sometimes throw up if they gobble their food. Separating kittens when feeding and/or feeding less food may help.
Intestinal parasites may also irritate the stomach.
Poisons and drugs
Ingesting poison or drugs can cause vomiting.
This is an immediate allergic reaction when a cat is exposed to an allergen. Acute anaphylaxis causes vomiting.
Cause: indigestible items and some diseases (infectious enteritis)
If it occurs over days or weeks and it is not linked to meals and the appetite is poor it might be foreign body in the stomach, liver or kidney disease, chronic gastritis, IBS, hairballs, worm infestation, diabetes mellitus, gastric or intestinal tumour in older cats.
Foreign body causing bleeding between mouth and upper small bowel.
Intestinal obstruction, peritonitis, trauma to abdomen.
Complete blockage in the upper gastrointestinal tract caused by foreign bodies, hairballs, tumour and strictures. Brain disease also a possible cause.
Kittens heavily infested with roundworms may vomit them.
Baterial infection of uterus
This is pyometra, a life threatening infection. The cat becomes toxic and runs a fever and vomits.
I am not qualified to advise on treatments. Sorry. Please see a vet if in doubt. I am afraid there is no other way although I understand the reluctance.
Some links to more on cat vomiting