Why Is My Dog Having Diarrhea At Night?

Why Is My Dog Having Diarrhea At Night? Photo of a dog at the toilet looking like he wants to poo

The honest truth is that there is never a good time for your dog to have diarrhea, but at night is probably the worst time. Wondering why this is a problem for your dog, in particular? Read on!

A sudden change in their food routine or content is the most common reason for your dog’s nighttime diarrhea. Other reasons could be a reaction to a new medication, allergies to their food’s ingredients, a parasite problem, or even anxiety or emotional distress.

Why is my dog having diarrhea every night?

To get a better understanding of loose bowels and what the cause could be for your dog’s tract, let’s focus on the most likely scenario of a sudden change of food. For example, you realize at supper time that you’ve completely run out of food for your dog and the corner store doesn’t have your brand, so you just select what looks best.

Your dog’s digestive tract is used to having a very certain kind of food with certain ratios of fat, protein, and nutrients. When it suddenly changes to something else entirely, the stomach and digestive tract are going to have a shock and it’ll start to evacuate the body because it hasn’t had time to learn how to digest this new kind of food. It’d be like switching from health food to takeout only, for humans (or vice versa). It may continue for a few nights until the body adjusts.

Medications and treatments

If your dog has started on a medication, such as a dewormer, you can also expect diarrhea for a few nights as the body puts it to work. This is considered normal and most often, your vet will warn you about it for that reason! This could also be the case if he is taking an antibiotic or anything else where it is working through his system.

Allergies and sensitivities

Allergies are common in many breeds, and a lot of them are common ingredients in your dog’s food! If you discover our dog having diarrhea in the evening and has his main meal at supper time, this is a (not-so) solid sign that it could be directly due to his food and its ingredients. It can help to (gently) transition him to an allergy-friendly food and see if that helps.

Parasites or illnesses

Other than food-related issues, many dog owners find that an undetected parasite problem is the most common cause of diarrhea at night time specifically. Parasites cause a lot of problems in the digestive tract of your dog, and fast-paced bouts of it, especially in the evening and overnight hours, is a pretty common problem! Roundworm, coccidia, and giardia, for example, are all known for causing nighttime diarrhea!

As well, if he’s eaten something he shouldn’t (chocolate, pesticides, etc), diarrhea is a common symptom to notice. This is often paired with other problems, too, such as panting, discomfort, and lack of appetite.

Anxiety and/or emotional distress

An anxious or emotional dog can also be prone to diarrhea, and this can often set in at night when he’s eaten and has been exercised out. Just like humans, the body physically responds when there is a sudden change in their life, including a move or a change of family status, etc. Even something as simple as bringing home another dog or pet could give him or her the runs as he adjusts. 

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Focused causes for dog diarrhea at night

Those examples are more for your general dog who is, more or less, outside of his puppy years and not yet into his golden years. There are other causes, however, that can relate to his puppy years and senior years when it comes to nighttime diarrhea!

Puppy diarrhea problems

If you’ve got a puppy, the main reasons are often the same as above, only a little less noticeable. So, it could be with food or emotional distress, but only a little change. While they may be subtle shifts (for example a new treat brand or going to a different dog park), they could be strong enough to cause a problem in your puppy’s stomach. 

Then there’s the fact that puppies with diarrhea are most often letting you know that something in their food is an allergy or sensitivity source. Since this is the beginning of their food exploration, this is when a lot of food allergies will show up! This is especially if you’ve just switched him (more on that later) from puppy food to adult food.

Senior diarrhea causes 

If you’ve got a dog in his golden years, the diarrhea causes could be any of the above examples, or it could be a signal that he’s starting to struggle a bit with his body controls. Again, this is similar to a human. It’s not uncommon to have small bladder leaks or bowel movements in life, and this is also the case with a senior dog. 

A dog who was previously able to control their bowel movements may start to have unplanned ones, especially at night when they are tired. It could be a fully formed bowel movement, but it is often diarrhea. While it isn’t a cause for concern, it is something to keep an eye on it, as it could be something more serious.

When should I worry about my dog’s diarrhea?

As gross and frustrating it is as a pet parent, a dog having diarrhea should not immediately cause a trip to the vet. Even in the healthiest dog, diarrhea happens every once in a while, and nighttime is a popular time frame for it. However, there are times where it could be concerning for his general health.

The most common sign that you may need a vet’s opinion is if you notice that the diarrhea isn’t stopping, or it’s getting worse. Every signal tonight for multiple nights, especially if you notice that it’s more and more frequent each night, should make you call your vet. Chronic diarrhea can cause dehydration as well as nutrition issues, so after a few days with no sign of it stopping, or it speeding up, take him to see what’s going on (don’t forget your sample).

If you notice his appetite changing, or that he’s drinking more than normal, or generally frantic and uncomfortable, especially in his tummy area, this is also a sign that he might be dealing with an issue such as illness, poison, or something else. Any time the diarrhea is paired with another kind of symptom, you should consider taking him to the vet.

If you notice that your dog just has one or two bouts of diarrhea, but is otherwise fine it’s most likely a passing disturbance. You can definitely let our vet know if you want, but one or two rounds of it can happen even to the perfectly taken-care-of dog!

What to do if your dog has diarrhea at night

Struggling through diarrhea and wondering how to help your dog feel better, as well as get some rest? Help is here.

First off, do whatever you can to help him stay as resistant as possible by paying attention to food changes. Since this is the most common cause, this is important. Transition him from one type of food to the other gradually. The same goes for treats and anything else that he may eat. This will help minimize the shock and keep his bowel movements normal (or, slightly runny.

If he is dewormed or given medication for another issue, you’ll want to make sure that you check with your vet about any kind of side effects, including diarrhea. Quite a few will be able to help you treat it at home, too (more on that next).

In terms of allergies, it’s more about making sure that you are aware of any new additions to the dog’s food and making sure that you watch for other signs of allergies (such as hives).

When in doubt, check with your vet! They are the professionals, after all, and are more than happy to help you get our dog back to normal!

You can consider giving your dog at-home treatments for diarrhea. These are vet-approved, too! The top options are:

  • Rice
  • Plain white bread
  • Mashed pumpkin (plain and pure, not a pie mix)
  • Special dog foods

For that last item, the dog food,s these are vet-designed brands that help calm the stomach naturally and provide them a gut-happy diet that can help those dogs who are prone to stomach issues.

While dog diarrhea is an awful topic to stomach — see what we did there? — it’s certainly better to know what to watch for, and how to help, than not!


Nighttime diarrhea is often caused by a sudden change in diet, allergies, or a parasite infection. While normal in all dogs from time to time, it can sometimes be a serious issue if it is ongoing. Try at-home remedies such as ride or bread, and check with your vet if any other symptoms pop up, or it doesn’t stop.

Like what you’ve learned? Share this with your fellow dog-owning friends and family so that you can all have a pantry stocked with stomach-friendly foods in case their dog gets the runs!

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Sara Santos

Writer, Editor and member of the Council, I am a dog person and I thrive to get the answers that will help you provide the best care a dog can have. You can also find me on my personal blog here.