Is Your Dog Peeing Indoors? The Real Reason Might Surprise You

You’ve done everything right—consistent potty breaks, praise when your dog goes outside, cleaning up accidents the moment they happen. And yet, you still find pee on your rug, or worse, on the side of your new couch. It’s easy to assume your dog just isn’t fully house trained.

But what if it’s not a training issue at all?

By around 12 months of age, most dogs are reliably house trained—so if your dog is still having accidents beyond that, there may be something else going on. Many dog owners are surprised to learn that urine marking—a completely different behavior from house soiling—might be to blame. Unlike accidents caused by a full bladder or confusion, marking is often a deliberate way for dogs to communicate, especially when something in their environment changes. And it’s not just a male dog thing—even spayed and neutered dogs can mark.

In this post, we’ll break down the difference between marking and potty accidents, why it matters, and what you can do to stop it. Because if you’re trying to fix the wrong problem, you might never get the results you’re hoping for.

What Is Marking?

Marking is your dog’s way of leaving a message—and it’s not “oops, I couldn’t hold it.” It’s more like, “I was here. This is mine. Move along.”

Unlike potty accidents, which happen when a dog has a full bladder and hasn’t learned where to go yet, marking is intentional. It typically involves small amounts of urine and is often triggered by territorial instincts, stress, or environmental changes—like a new pet, visitor, or even a different piece of furniture.

Some dogs feel compelled to mark their territory—like my dog Bella—but with training and clear boundaries, she knows it’s only allowed outside.

Bella is a mini poodle–rat terrier mix with a strong opinion on real estate. She’s fixed, fully house trained, and has never marked indoors. But outside? That’s a different story. Bella firmly believes the entire neighborhood belongs to her. Every mailbox, fencepost, and innocent blade of grass is fair game. If another dog has been there, she knows—and she’s not shy about correcting the oversight.

She doesn’t just go for walks—she goes on territorial inspection tours.

Dogs like Bella are a perfect example of how marking isn’t about a lack of training. It’s rooted in instinct and communication. Terrier breeds, in particular, were bred to be alert, active, and aware of their surroundings—often defending territory from small critters or other animals. That mindset carries over, even in our suburban setting.

While marking is more common in un-neutered males, spayed and neutered dogs can and do mark, especially if they’re naturally territorial, anxious, or responding to new scents or social dynamics.

In fact, a 2012 study titled Scent-Marking Behaviour in a Pack of Free-Ranging Domestic Dogs found that dogs use urine marking as a form of communication—especially to establish territory and social rank. The researchers observed that high-ranking dogs marked more often, especially in areas they considered important. You can read the study here: ResearchGate: Scent-Marking Behaviour in a Pack of Free-Ranging Domestic Dogs

Check for Medical Issues First

Before assuming your dog is marking or having potty training setbacks, it’s important to rule out any underlying health issues. Dogs—especially as they age—can experience changes in bladder control or develop conditions that make it difficult to “hold it,” even if they’ve been house trained for years.

Health Conditions That Can Cause Indoor Urination

• Urinary Tract Infections (UTIs)
• Bladder or kidney stones
• Diabetes
• Cushing’s disease
• Incontinence (common in senior or spayed females)
• Cognitive dysfunction in older dogs

These issues can lead to sudden, frequent, or uncontrollable urination, and often catch owners by surprise.

Our Story

Years ago, our English Springer Spaniel—completely house trained and well-behaved—suddenly began having accidents in the house around age 10. This was completely out of character. She hadn’t peed indoors since she was a young puppy, and now it was happening frequently—not just the occasional slip-up.

We knew something wasn’t right, so we brought her to the vet. Sure enough, she had a urinary tract infection. After starting treatment, the accidents stopped completely.

How to Distinguish Marking from Accidents

If your dog is still peeing in the house, the first step is figuring out why. Is it a potty training issue—or are they marking? The two behaviors can look similar at first, but there are some key differences that can help you tell them apart.

Age Matters

By about 6 months of age, most large breed dogs are fully house trained. Smaller breeds can take a bit longer—sometimes up to 8 or even 12 months—especially if they have small bladders or if training has been inconsistent.

So if your dog is past that age range and still having “accidents,” it’s worth asking if the issue might not be an accident at all.

Key Differences Between Marking and Potty Accidents

Volume

• Marking: Typically just a few drops or a small squirt—barely enough to require a paper towel.
• Accident: A larger puddle, often the result of a full bladder that wasn’t emptied in time.

Location

• Marking: Dogs tend to target vertical surfaces—walls, furniture legs, the side of a couch. They’re not just relieving themselves; they’re sending a message.
• Accident: Happens on horizontal surfaces like rugs, tile, or the middle of the floor—usually wherever the dog happens to be when they couldn’t hold it any longer.

Timing

• Marking: Often happens shortly after something has changed in the dog’s environment—like a visitor arriving, a new pet in the home, or even bringing in a new piece of furniture. It’s a response to stimulation or stress.
• Accident: More likely to occur when a dog hasn’t been let out in time, after waking up, eating, or drinking—especially if they’re young or have a medical issue.

Behavioral Signs

• Marking: Dogs will often sniff the area first, then lift their leg (or sometimes squat) and release a small amount of urine—then move on like it was just another item checked off their to-do list. There’s a clear sense of purpose to the action.

Take Bella, for example, when she actually needs to relieve herself, she squats like any well-trained female dog. But when she’s marking? That’s when she gets clever. Despite being small she’ll lift her leg and aim high, just like the boys do. She wants to make sure her scent is placed strategically—as high as possible on a pole, bush, or signpost—so every other dog in the neighborhood knows she was there.

• Accident: A dog having a potty accident usually looks more distracted or anxious, especially if they weren’t sure how to let you know they needed to go out. There’s often no sniffing or clear preparation—just a sudden squat or release. Some dogs may even look guilty or confused afterward, especially if they’ve been scolded for it in the past.

How to Stop Indoor Marking

Once you’ve confirmed your dog is healthy and not dealing with a medical issue, it’s time to address marking behavior directly. The good news is that indoor marking can usually be managed or even eliminated with the right approach, as long as you stay consistent.

1. Clean Marked Areas Thoroughly

Dogs are drawn to spots they’ve marked before—or where other dogs have peed. Use a high-quality enzymatic cleaner to break down the odor completely. Avoid ammonia-based cleaners, which can actually mimic the smell of urine and encourage more marking.

2. Limit Access to Problem Areas

If your dog repeatedly marks the same room, piece of furniture, or doorway, block off that area when you’re not around. Baby gates, closed doors, or crate training can help manage where your dog roams until the behavior improves.

3. Watch for Pre-Marking Behavior

Many dogs show signs before they mark: sniffing a surface intensely, pacing, or lifting a leg. If you catch them in the act, interrupt with a firm “no” and immediately take them outside. Then praise if they mark outdoors instead.

4. Address Stress and Triggers

Marking is often an emotional response to a change. Ask yourself:

• Has a new pet or person entered the home?
• Have routines shifted?
• Are you seeing signs of anxiety or insecurity?

Try to identify and ease the underlying stress. Increasing exercise or working with a trainer can help reduce tension that leads to marking.

5. Spay or Neuter (If You Haven’t Already)

Hormones play a significant role in marking—especially in unneutered males and, to a lesser extent, unspayed females. That’s because testosterone and estrogen can increase territorial behavior and the urge to advertise reproductive availability. Urine marking isn’t just about claiming space—it can also be a signal to other dogs about a dog’s presence, status, and even readiness to mate.

This is why intact dogs are much more likely to mark, especially in response to new smells, other animals, or changes in the environment. Spaying or neutering usually lowers hormone levels, which in turn can reduce the drive to mark—particularly if it’s done before the behavior becomes a habit.

That said, it’s not a guaranteed solution. Bella, our rescue dog, was spayed at just 9 weeks old. Despite that, she still began marking her territory as an adult. In her case, the behavior isn’t about hormones—it’s about instinct. For many dogs, especially those with strong territorial or alert temperaments, marking can still occur even without the hormonal influence.

6. Go Back to House Training Basics

Even if your dog is technically house trained, a refresher never hurts. Set a consistent potty schedule, reward outdoor marking, and supervise when indoors. For persistent cases, short-term use of belly bands (for males) or doggy diapers (for females) can help manage the mess while you retrain.

When to Call a Professional

If you’ve tried cleaning, supervision, routine changes, and basic behavior correction—and your dog is still marking indoors—it may be time to call in a certified dog trainer or behaviorist. A professional can help identify subtle triggers, customize a training plan, and rule out more complex behavioral issues like anxiety or resource guarding.

Final Thoughts

If your dog is peeing in the house past the typical potty training window, don’t assume it’s just bad behavior—or that your training failed. The cause could be marking, especially if the accidents are small, frequent, or triggered by changes in the home.

Start by ruling out medical issues, especially if the behavior is new or sudden. If your dog checks out healthy, take a closer look at their environment, emotional state, and habits. Knowing the difference between accidents and marking makes all the difference when it comes to correcting the problem.

The good news? With patience, structure, and a little detective work, most marking behavior can be managed or eliminated entirely.

Have you dealt with indoor marking or surprise accidents from a fully house-trained dog?

We’d love to hear your experience. Share your story in the comments—what helped, what didn’t, and what you learned along the way. Your insights could help another dog owner going through the same thing.