Most vets reach for polyethylene glycol 3350 or lactulose when a dog is constipated, but the dose and choice always come from a veterinarian.
For the full breakdown, see our best Dog Laxative guide.
A dog who has not pooped in two days needs a phone call, not a leftover human laxative from the medicine cabinet. Handing over the wrong product can turn a simple case of constipation into a blockage that only a clinic can clear.
Veterinarians settle what laxative you can give a dog by first working out why the stool stopped. Hard, dry feces from low water intake behave nothing like a blockage, a mass, or an injury. Mild cases have well-known answers; the rest need hands on the belly first, and the table below sorts what a vet may use from what you should never hand over.
Laxatives For Dogs: What Vets Reach For First
Polyethylene glycol 3350 — sold for people as MiraLAX — and lactulose are the two laxatives veterinarians reach for most often in dogs. Both pull water into the colon instead of forcing the gut to spasm. PetMD lists lactulose among the medications used for canine constipation, and polyethylene glycol 3350 is where owners most often go wrong, because a human label dose has nothing to do with a dog.
Milder cases often need less than a drug. Extra water, more fiber, and a longer walk can be enough on their own, and plain canned pumpkin is the fiber source vets mention most. When feces are packed too tight to pass, a veterinarian may remove them by hand or run a clinic enema.
| Option | How Vets Use It | Main Risk |
|---|---|---|
| Polyethylene glycol 3350 | Osmotic laxative, dosed by
|