A few human laxatives are commonly used in cats under veterinary guidance, but the doses are drastically smaller than what you’d take yourself, and some products that seem harmless to people can be fatal to cats. The safest options fall into two categories: osmotic laxatives that draw water into the stool, and stool softeners that help things pass more easily.
Miralax (PEG 3350)
Miralax is the most widely recommended human laxative for cats. It’s an osmotic laxative, meaning it pulls water into the colon to soften stool. It’s flavorless, dissolves easily, and most cats don’t notice it in food. A study published in the journal of the National Center for Biotechnology Information tested PEG 3350 specifically in cats and found it both safe and palatable, with a median effective daily dose of about 3 grams for an average cat.
In practice, most cat owners start much lower. A common starting point is 1/8 teaspoon mixed into wet food twice a day, increasing gradually if there’s no bowel movement within 48 hours. Some cats need as little as 1/16 teaspoon twice daily, while others end up closer to 3/4 teaspoon per day. The key is to start small and adjust. Mixing it into wet food with a splash of water works well. Adding a couple teaspoons of plain canned pumpkin (not pie filling) can help mask any texture change and adds fiber that supports the laxative’s effect.
Lactulose
Lactulose is a sugar-based syrup that works similarly to Miralax by drawing water into the intestine. It’s technically a prescription product in some countries but is available over the counter in others. Veterinarians frequently prescribe it for cats at a dose of 1 to 3 mL (roughly a half teaspoon) twice a day. It has a sweet taste that some cats tolerate and others refuse. The main downside is that it can cause gas and cramping if the dose is too high, so you’d want to start at the lower end.
Docusate Sodium (Colace)
Docusate sodium is a stool softener rather than a true laxative. It works by helping water and fats mix into hard stool, making it easier to pass. Veterinarians sometimes use it for mild constipation, and pediatric rectal suppositories containing docusate sodium are also used in cats. However, there’s one important rule: never give docusate sodium at the same time as mineral oil. Docusate increases how much the intestinal lining absorbs, and combining it with mineral oil can push oil into the bloodstream, causing serious problems.
Psyllium Husk (Metamucil)
Unflavored psyllium husk powder, the active ingredient in plain Metamucil, acts as a bulk-forming fiber supplement. It absorbs water and adds moisture and mass to stool, which can stimulate the colon to move things along. A study in healthy cats found that a diet containing 6% psyllium increased both how often cats defecated and how moist their stool was. For home use, a small amount (typically around 1/2 teaspoon) mixed into wet food once or twice daily is a reasonable starting point. Use only the unflavored, sugar-free version. Flavored Metamucil contains sweeteners like xylitol that are toxic to animals.
Human Laxatives That Are Dangerous for Cats
Not everything in your medicine cabinet is safe, and one product in particular is potentially lethal. Fleet enemas and any other sodium phosphate enemas should never be used in cats. A veterinary case report documented life-threatening metabolic collapse in two cats after sodium phosphate enema use, including dangerously high sodium levels, plummeting calcium, seizures, and severe dehydration. The cats in that report survived, but a dog in the same study did not. The small body size of cats makes them extremely vulnerable to the electrolyte shifts these products cause.
Stimulant laxatives like bisacodyl (Dulcolax) are sometimes used by veterinarians in specific situations, but they work by forcing the colon to contract and should not be given at home without direction. Anything containing xylitol, artificial sweeteners, or flavoring agents is also off the table.
When Constipation Signals Something Bigger
Simple constipation in cats looks like straining in the litter box and producing small, hard, dry feces. Many cats get backed up from dehydration, low-fiber diets, or not enough activity, and a gentle laxative resolves it. But constipation can also be a symptom of a more serious condition called megacolon, where the colon stretches out and loses its ability to push stool forward. Cats with megacolon may respond to laxatives early on, but chronic or worsening cases often require surgery.
If your cat hasn’t had a bowel movement in more than two days, is vomiting, refusing food, acting lethargic, or passing thin ribbon-like stool, those signs point beyond simple constipation. Ribbon-shaped feces can indicate something is physically narrowing the passage, like a mass or swollen tissue. Vomiting alongside constipation is especially common in cats and suggests the backup is significant enough to affect the whole digestive system.
Practical Tips for Giving Laxatives
Cats are notoriously picky, so getting a laxative into them requires some strategy. Miralax and psyllium dissolve or blend well into wet food, especially if you add warm water to make it slightly soupy. Lactulose is a liquid and can be syringed directly into the mouth, though mixing it into food is less stressful for everyone. Whichever product you use, offer it with a small portion of food first to make sure your cat eats the full dose before getting the rest of their meal.
Hydration matters as much as the laxative itself. Osmotic laxatives work by pulling water into the colon, so a dehydrated cat won’t get the full benefit. Encouraging water intake through a pet fountain, adding water to wet food, or offering low-sodium broth alongside meals helps the laxative do its job. Many chronic constipation cases in cats improve significantly just by switching from dry food to wet food, since wet food contains roughly 75% water compared to about 10% in kibble.