Docusate sodium is the most commonly recommended stool softener for dogs, and it’s the same active ingredient found in many over-the-counter human products. Polyethylene glycol 3350 (the active ingredient in MiraLAX) and lactulose are also used safely in dogs. That said, the right choice and dose depend on your dog’s size and overall health, so confirming with your vet before giving anything is the smartest move.
Docusate Sodium: The Standard Option
Docusate sodium works by lowering the surface tension of stool, which lets water penetrate and accumulate in the feces. The result is softer, easier-to-pass bowel movements. The MSD Veterinary Manual lists the canine dose at 2 mg per kilogram of body weight, given by mouth once daily. For a 50-pound dog, that comes out to roughly 45 mg per dose.
Side effects are generally mild. At excessive doses, dogs may experience diarrhea, vomiting, or loss of appetite. Liquid and syrup forms can irritate the throat and taste bitter, so giving them with plenty of water or mixing them into food helps. Docusate should not be used if your dog is vomiting, has a painful or bloated abdomen, or might have an intestinal blockage, because the medication can mask a more serious underlying problem.
Polyethylene Glycol 3350 (MiraLAX)
Polyethylene glycol 3350 is a water-soluble polymer that draws water into the intestine, bulking and softening the stool. It’s widely available as an unflavored powder and can be stirred directly into your dog’s regular food. Many veterinarians recommend it as a gentle, short-term solution for mild constipation because it doesn’t stimulate the gut the way stronger laxatives do. Your vet will tailor the amount to your dog’s weight, so call before scooping a dose on your own.
Lactulose: A Prescription Option
Lactulose is a synthetic sugar syrup that pulls water into the colon through osmosis. Veterinarians prescribe it for dogs with chronic constipation or liver problems, where reducing ammonia levels in the blood is also a goal. It comes as a liquid syrup or crystal granules and can be mixed into food. Because it requires a prescription and careful dosing, lactulose is typically reserved for cases where over-the-counter options haven’t worked or when a dog has an underlying liver condition.
Plain Canned Pumpkin and Psyllium
For dogs with occasional, mild constipation, dietary fiber can be enough to get things moving without any medication at all. Plain canned pumpkin (not pie filling, which contains sugar and spices) is the most popular home remedy. Small dogs can have 1 to 2 teaspoons per day, while medium and large dogs can handle 1 to 2 tablespoons. The high moisture and fiber content softens stool naturally.
Powdered psyllium husk, the same fiber found in products like Metamucil, is another option. Choose an unflavored, unsweetened version and sprinkle it over your dog’s food. Both pumpkin and psyllium work best when your dog is drinking plenty of water, since fiber needs fluid to do its job.
Ingredients That Are Dangerous to Dogs
Not every human stool softener or laxative is safe. The biggest threat hiding in some products is xylitol, a sugar substitute also labeled as “birch sugar” or “wood sugar.” Xylitol shows up in sugar-free gummies, chewable supplements, flavored fiber products, liquid medicines, and even some cough syrups. In dogs, xylitol poisoning can begin within 20 minutes and cause vomiting, weakness, seizures, liver failure, and death.
Before giving your dog any human product, read the full ingredient list. Avoid anything containing xylitol, artificial sweeteners you don’t recognize, or stimulant laxatives like bisacodyl or senna, which can cause dangerous cramping and electrolyte imbalances in dogs. Some liquid docusate formulations also contain propylene glycol, which can be toxic in high doses or with prolonged use. Stick to plain, unflavored versions of any product.
Signs Your Dog Needs More Than a Stool Softener
Mild constipation, where your dog strains a bit but is otherwise acting normal, is usually manageable at home for a day or two. But if your dog hasn’t had a bowel movement within 48 to 72 hours of the last one, it’s time to call the vet. Other warning signs include vomiting, decreased appetite, weight loss, passing only small amounts of watery or mucus-coated feces without a normal stool, or a visibly tense abdomen. Some constipated dogs cry or growl when you press on their stomach or lower back, which can signal pain from a blockage or impaction that a stool softener alone won’t resolve.
Constipation in dogs sometimes points to something beyond diet: dehydration, a swallowed foreign object, a tumor, or a neurological problem affecting the colon. A stool softener treats the symptom, not necessarily the cause. If constipation comes back repeatedly or doesn’t improve within a couple of days of treatment, your vet can run imaging or bloodwork to figure out what’s going on underneath.