Cat Throwing Up Grass: Why Cats Eat Grass and Vomit
By Dr. Zubair Khalid, DVM, MS, PhD ·
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Cats eat grass for reasons that are not fully understood, and many of them vomit it back up shortly afterward. In most cases, a cat throwing up grass once in a while is not a sign of illness. The pattern matters more than the single event, so repeated grass eating followed by vomiting deserves a closer look.
Quick Answer
- Occasional grass eating and vomiting is common in cats and often harmless.
- Grass has no nutritional value for cats, and it can irritate the stomach lining and trigger vomiting.
- If your cat keeps eating grass and throwing up, that pattern can point to nausea or an underlying gastrointestinal problem.
- Vomiting that happens many times in a day, comes with lethargy, or stops your cat from eating is a reason to call your veterinarian.
- Never give your cat human anti-nausea medicine or any medication without veterinary guidance.
What Cat Throwing Up Grass Looks Like
Most owners describe a pile of green blades mixed with clear or yellowish fluid. Sometimes the grass comes up with a small amount of white foam. Sometimes it comes up with undigested food or a hairball. The volume is usually small, and the episode is over in seconds.
A normal, isolated episode looks like this. Your cat eats grass outdoors or from a container, vomits once or twice within a short time, then goes back to normal behavior. Appetite, energy, and litter box habits stay the same. This kind of event does not usually need treatment.
A concerning pattern looks different. Your cat seeks out grass again and again, vomits repeatedly, and seems uncomfortable between episodes. You may notice lip licking, swallowing, or restlessness before the vomit comes up. These are signs of nausea, and nausea is a symptom, not a diagnosis.
If your cat is bringing up white foam along with the grass, that combination has its own set of causes worth reviewing. You can read more about it in My Cat Threw Up White Foam And Grass.
Why Does My Cat Eat Grass Then Vomit?
Veterinarians do not have one proven answer. Several theories exist, and more than one may be true for any given cat.
One common theory is that grass helps cats bring up hairballs. Cats swallow loose hair while grooming, and hair cannot be digested. It clumps in the stomach and can form a hairball, also called a trichobezoar [1]. Many cats vomit up the hairball, though in some cases it stays in the stomach for a long time and hardens into a dense mass that can irritate the stomach or block the digestive tract [1]. Longhaired breeds face a higher risk [1].
Another theory is that grass triggers a reflex that empties the stomach of something irritating. The plant material itself can scratch the stomach lining, which may be enough to cause vomiting.
A third possibility is simpler. Some cats just like the texture and taste of grass. They eat it, their stomach reacts, and they vomit. There is no illness involved.
What is clear is that grass provides no meaningful nutrition to a cat. Cats are obligate carnivores, and their digestive tract is built for meat.
Main Causes of Grass Eating and Vomiting
| Cause | Typical clues | How urgent |
|---|---|---|
| Normal grass eating behavior | One or two vomits, cat acts normal right after, appetite and energy unchanged | Not urgent, monitor at home |
| Hairballs | Vomit contains hair, longhaired breed, episodes every few weeks | Routine visit if frequent |
| Nausea from any cause | Lip licking, drooling, repeated swallowing, grass seeking, vomiting several times a week | See a veterinarian soon |
| Gastrointestinal disease | Weight loss, poor appetite, diarrhea, vomiting that gets more frequent over time | See a veterinarian soon |
| Viral or infectious GI illness | Sudden vomiting and diarrhea, often in a shelter or multi-cat home | Same-day call |
| Foreign body or blockage | Vomiting that will not stop, no stool, belly pain, lethargy | Emergency now |
Feline chaphamaparvovirus, sometimes called feline fechavirus, has been found in vomit and feces from cats, including cats in shelters with clusters of sudden vomiting and diarrhea [2]. This is one example of an infectious cause that a veterinarian may consider when several cats in one home or facility get sick at the same time.
When Grass Vomiting Is Harmless
A single episode of vomiting grass in a cat that otherwise feels fine is usually not a problem. Watch your cat for the next 24 hours. If appetite, energy, drinking, and litter box habits stay normal, you can likely just keep an eye on things.
Some cats vomit grass a few times a year. Others never do. Both can be normal.
The picture changes when vomiting becomes a habit. A cat that vomits grass once a week, or several times a month, is not having isolated events. That frequency suggests something is driving the behavior, and nausea is the most likely explanation.
Red Flags That Make It an Emergency
Call your veterinarian right away or go to an emergency clinic if you see any of these.
- Vomiting more than a few times in one day, or vomiting that will not stop
- Your cat cannot keep water down
- Your cat is weak, wobbly, or hard to wake
- The belly looks swollen or feels painful when touched
- Your cat is straining to vomit with nothing coming up
- You suspect your cat ate a toxic plant, string, toy, or human medication
- There is blood in the vomit
- Your cat has not passed stool and seems uncomfortable
Repeated vomiting can lead to dehydration quickly, especially in kittens, senior cats, and cats with other health conditions. Do not wait to see if it resolves on its own when these signs are present.
Safe Things You Can Do at Home
If your cat vomited grass once and seems fine, you can take a few simple steps while you watch for changes.
Remove access to the grass source. If your cat eats grass from a houseplant, move the plant out of reach. If your cat goes outside, keep them indoors for a day or two. This helps you see whether the vomiting stops when the grass is gone.
Offer small amounts of water. Do not let your cat gulp a large bowl at once. Small, frequent sips are easier on the stomach.
Skip one meal, then offer a small bland meal. Many veterinarians suggest withholding food for a short time, then offering a small portion of your cat's regular food. Ask your own veterinarian how long to wait, because the answer depends on your cat's age and health.
Do not give human anti-nausea drugs. Never give your cat medication meant for people unless your veterinarian tells you to. Some common human drugs are toxic to cats.
Do not force your cat to eat. If your cat refuses food for more than 24 hours, call your veterinarian.
Keep notes. Write down how often the vomiting happens, what it looks like, and whether grass or hair is present. This information helps your veterinarian narrow down the cause.
If your cat is vomiting undigested food along with the grass, that pattern is covered in Cat Throwing Up Food Undigested.
What Your Veterinarian Will Check
Your veterinarian will start with a full history. They will ask how often the vomiting happens, what it looks like, whether your cat goes outside, and whether there have been changes in appetite, weight, or stool.
The physical exam checks hydration, body condition, belly comfort, and the mouth and teeth. Your veterinarian will also feel for any masses or thickened loops of intestine.
Depending on what they find, they may recommend:
- Blood work to check organ function and look for signs of inflammation or infection
- A fecal test to look for parasites
- X-rays or ultrasound to look for a foreign body, hairball mass, or other blockage
- A hairball or diet trial if hairballs seem to be the main issue
If your cat is vomiting from a known trigger, your veterinarian may use a medication to control nausea. Maropitant is one drug that has been shown to reduce vomiting risk in cats in controlled studies [3]. Other antiemetics exist, and your veterinarian will choose based on your cat's specific situation. The dose is calculated from your cat's weight and health, so never use a leftover medication from a previous visit.
In some emergency situations, veterinarians induce vomiting on purpose when a cat has eaten something toxic. This is a controlled procedure done in a clinic. Detomidine gel given through the mouth lining induced vomiting in about half of cats in one study, with a median time to vomiting of 11 minutes [4]. Orally administered dexmedetomidine at 20 µg/kg induced vomiting in five of six cats in a small case series [5]. These are clinic procedures, not something an owner should attempt at home.
Prevention and Monitoring
The best prevention depends on the cause.
If hairballs are the issue, brush your cat regularly, especially if you have a longhaired breed. Talk to your veterinarian about diets or products designed to help hair move through the digestive tract.
If nausea is the issue, treating the underlying cause is the only real fix. Removing grass will not stop the vomiting if the stomach is already upset.
If your cat eats grass out of boredom, add more play and environmental enrichment. Some cats chew plants when they have nothing else to do.
Keep a simple log. Note the date, what came up, and how your cat acted afterward. Bring it to your next appointment. Patterns that are hard to see day to day become obvious on paper.
If your cat keeps eating grass and throwing up, that is the pattern to bring to your veterinarian. A single episode is rarely a concern. A repeating cycle is worth a conversation.
For a deeper look at the difference between normal grass vomiting and GI disease, see Why Is My Cat vomiting after eating grass? Normal Behavior vs GI Disease.
Limitations and When to Contact a Veterinarian
This article cannot tell you what is happening with your specific cat. Only a veterinarian who examines your cat can do that.
Call your veterinarian the same day if your cat vomits more than two or three times in a day, refuses food, seems painful, or has diarrhea along with the vomiting.
Go to an emergency clinic now if your cat is vomiting constantly, cannot hold water down, is weak or unresponsive, has a swollen or painful belly, or if you suspect poisoning or a swallowed object.
Schedule a routine visit if the grass eating and vomiting happens more than once a month, if your cat is losing weight, or if you have noticed any change in appetite or energy over weeks.
Frequently Asked Questions
Should I stop my cat from eating grass?
It depends on the pattern. If your cat eats grass rarely and vomits once with no other signs, you can leave things alone. If your cat seeks out grass and vomits often, remove access and talk to your veterinarian about the underlying cause.
Is grass bad for cats?
Grass itself is not toxic to cats. The problem is what it does to the stomach. Plant material can irritate the lining and trigger vomiting, and outdoor grass may carry pesticides or parasites.
Can grass help my cat pass a hairball?
Grass may help some cats bring up a hairball, but there is no proof it works reliably. Hairballs that stay in the stomach can harden and cause irritation or a blockage, so frequent hairball vomiting is worth a veterinary visit.
My cat vomits grass but acts fine. Do I need a vet visit?
A single episode in a cat that eats, drinks, plays, and uses the litter box normally is usually not urgent. If it happens repeatedly, or if anything else changes, call your veterinarian.
Can I give my cat anti-nausea medicine from my own cabinet?
No. Never give your cat human medication without veterinary direction. Some common anti-nausea and pain drugs are toxic to cats, and the correct feline dose must be set by a veterinarian based on your cat's weight and health.
Related Articles
- Why Is My Cat vomiting after eating grass? Normal Behavior vs GI Disease
- My Cat Threw Up White Foam And Grass
- Cat Throwing Up Food Undigested
- Why Is My Cat Throwing Up White Foam And Food
- Dog Eating Grass and Vomiting: Normal or a Problem?
- My Cat Is Throwing Up Undigested Food
- Why Is My Cat Eating Grass and Plants?
- Is Grass Safe for Cats to Eat? Cat Grass and Seeds
- Cat Throwing Up Spit, Saliva, or Foam: Causes
References
- Vomiting in Cats - Cat Owners. Merck Veterinary Manual.
- Feline chaphamaparvovirus (feline fechavirus) in different cat populations. Journal of feline medicine and surgery, 2026.
- Receptor-Targeted Antiemetic Strategies in Cats: A Systematic Review and Intervention-Specific Meta-Analysis. Veterinary medicine and science, 2026.
- Transmucosal detomidine gel induces emesis in approximately half of cats presenting for dietary indiscretion. Journal of the American Veterinary Medical Association, 2026.
- Use of orally administered dexmedetomidine to induce emesis in cats. Journal of feline medicine and surgery, 2024.