It’s possible that your dog may be sick for a long time and you may not even know it. In today’s article, I’m going to share some tips that can help you determine if your dog is sick and what signs indicate that your dog may be sick or is about to become sick.
My dog became very sick during the winter, so I took him to the doctor. The first thing the doctor asked me was, “Why didn’t you bring him in earlier?” I had no idea this dog was sick. The doctor said, “How did you go so long without realizing it?”
I asked the doctor if he could tell me what signs dogs show that indicate a dog might be sick. He gave his opinion and offered some tips, which I’ll share with you. Also, during my research, I discovered some facts that might surprise you.
Key takeaways
- Dogs hide illness by instinct. You won’t get a dramatic sign. You’ll get small ones.
- Appetite and bathroom habits are the two easiest things to track daily.
- Any symptom that lasts more than 24 hours, or comes with a second symptom, is a vet visit, not a wait-and-see.
- Some signs (pale gums, a bloated stomach, trouble breathing) mean go now, not tomorrow.
Common Signs Your Dog May Be Sick
Start With the Food Bowl
My vet told me that if you want to find out whether your dog is sick or not, the first thing to do is observe his appetite. The easiest way to see is how much he eats and whether there has been any sudden change in his eating habits.
Most dogs eat every meal with great excitement. So if a dog that normally finishes his breakfast or dinner quickly suddenly starts ignoring food, it’s something to pay attention to.
Eating less is not the only sign of a problem. Sometimes, a sudden increase in appetite can also indicate a health issue, such as worms or diabetes. Therefore, if your dog suddenly becomes more hungry than before, don’t ignore it thinking it’s normal.
Missing a meal is usually not a serious matter. My vet said the same thing. However, if your dog doesn’t eat for the next few days or his behavior doesn’t seem normal, you should contact the vet.
Bathroom Habits Tell You a Lot
For the next 24 hours, keep an eye on whether your dog is going to the bathroom normally. Also, keep an eye out for symptoms like vomiting or diarrhea. Dogs often hide their discomfort, so it’s our responsibility to observe them. My vet also gave me the same advice.
This habit has been very useful for me. A single loose stool or vomiting isn’t always an emergency. If your dog seems normal in everything else and has only vomited once, it’s not necessary to go to the vet immediately.
However, in some situations, you shouldn’t wait. If your dog is vomiting frequently, has very watery diarrhea, blood in the vomit or stool, refuses food or water, doesn’t behave normally, or doesn’t improve after 24 hours, you should contact the vet.
Another important thing I didn’t realize before: If your dog is retching frequently and their stomach appears swollen, it could be a sign of GDV (twisted stomach). This is a life-threatening emergency, and every minute counts. I’ll discuss this in more detail later in the article.
If it’s just diarrhea, follow the same 24-hour rule. If it’s been less than 24 hours and the dog is otherwise normal, you can observe the dog’s condition at home. However, if the diarrhea lasts longer than 24 hours, the dog is very young or very old, has a pre-existing health problem, or just doesn’t seem normal, it’s best to contact a vet.
Watch How Much They’re Moving (and How Much They’re Not)
This was a sign I didn’t recognize with my own dog. When a dog’s energy starts to wane, it doesn’t always seem serious. Often, it seems like they’ve become lazy, slowed down due to age, or are acting out because of the heat.
Sometimes this is indeed the case, but not always. If your dog is sleeping more than before, lagging behind on walks, or not showing as much interest in playing as before, it could be a sign of a health problem. Infections, heart disease, breathing problems, or hormonal issues like low thyroid can also cause a dog’s energy to decrease. If these changes persist for more than a day, you should consult a veterinarian.
Don’t ignore changes in behavior. If your dog suddenly becomes more quiet, sits in a different place, avoids touch, or becomes aggressive or irritable for no reason, don’t dismiss it as a mood. This can also be an important sign that something is not right.
Breathing Changes Are Easy to Miss Until They’re Not
Healthy dogs breathe quietly and evenly. You don’t think about it because there’s nothing to notice.
That’s exactly why a change matters. Coughing, wheezing, rapid breathing, or laboured inhalation may point to a respiratory infection, heart disease, or allergies, and it’s the kind of thing that’s easy to write off as “he’s just been running around” until you realise he’s been sitting still for ten minutes and still breathing hard.
Pale or blue gums are a different tier entirely. That can mean a lack of oxygen, and it should be treated as an emergency, not something to monitor overnight.
Skin, Coat, and Scratching
A healthy coat is shiny and reasonably clean. Sudden hair loss, excessive scratching, redness, or flaky skin can point to allergies, parasites, or infection.
If your dog’s skin problem shows up specifically as a rash on the belly, with scratching, licking, or biting alongside it, I’ve gone into that in more depth in my guide to belly rashes in dogs. It walks through what’s a same-day vet visit versus what you can manage at home.
One thing worth knowing here: the anal glands can also cause scratching-type behaviour that has nothing to do with skin at all. If you notice your dog excessively licking their bottom, nibbling the base of their tail, or “scooting” across the floor, that’s usually blocked anal glands, and it’s worth a vet visit if it keeps happening.
Drinking More, or Drinking Less
Both directions matter here, which surprised me.
If your dog is constantly draining the water bowl, asking to go out more often, or having accidents in the house, that’s called polydipsia, and it can point to something like diabetes, Cushing’s disease, kidney disease, or a severe uterine infection, especially if it’s been going on for more than a day or two and it isn’t just a hot day.
Drinking noticeably less is its own warning sign too, often paired with reduced appetite. Either extreme, tracked against what’s normal for your dog, tells you something.
Weight Changes You Didn’t Cause
If you haven’t changed your dog’s food or portions and their weight is shifting anyway, that’s not a diet issue. That’s a health issue.
Weight loss alongside diarrhoea, low energy, vomiting, or yellowing (jaundice) can point to something like liver disease. A dog gaining or losing weight for no obvious reason is one of the clearer signals that something needs a vet’s attention rather than a food swap. If your dog does have a genuinely sensitive stomach and you’re trying to work out what’s diet-related versus what isn’t, I’ve broken that down separately in my guide to feeding dogs with sensitive stomachs.
Signs of Pain Are Often Quiet
Dogs don’t announce pain the way we’d expect. There are really two ways to catch it.
The first is behaviour you already know is off. You know your dog’s normal behaviour best, so if they’re acting out of character, that alone can be a sign they’re in pain. The second is physical: a dog yelping when picked up, growling when their tummy is touched, or standing in a “prayer position” with front legs down and hind legs up, which is a specific and recognisable sign of stomach pain.
Don’t reach for human painkillers here. Contact your vet instead. Some human pain medication is genuinely dangerous for dogs.
When It’s Not “Wait and See” Anymore
Most of what’s above is about noticing early. This part is about acting fast.
Bloat (GDV) is the one my vet drilled into me hardest. It’s when the stomach fills with gas and can twist, cutting off blood supply to the gut and sometimes the spleen too, and it can kill within hours without treatment. Signs include a swollen, hard belly, retching without bringing anything up, restlessness, and drooling. If you think your dog has bloat, don’t call in the morning. Get them to a vet immediately.
A few other signs that mean the same thing, go now rather than later:
- Trouble breathing, or pale or blue gums
- Collapse, or an inability to stand
- Vomiting that’s continued for more than 12 hours
- Inability to urinate
- Blood in urine, vomit, or stool
None of these are “monitor for a day.” They’re emergency calls.
How I Actually Keep on Top of It Now
After that winter, I changed how I pay attention to my dog. Nothing complicated, just a few habits.
I keep a rough note of what he eats and how much, so a missed meal actually registers instead of blending into the week. I check him over during grooming, running a hand over his coat and under the fur for any lumps, since that’s an easy way to catch something before it grows into a bigger problem. And I stopped treating “he seems a bit off” as nothing. If it’s still there the next day, I call the vet.
You know your dog best. If something feels wrong and it doesn’t fit neatly into any list, including this one, that instinct is still worth listening to.
Frequently Asked Questions
How do I know if my dog is seriously sick?
Persistent vomiting, trouble breathing, sudden collapse, pale gums, or a swollen tight belly are red flags that need immediate veterinary attention, not a wait-and-see approach.
Can a dog hide being sick from me?
Yes, and this is the core problem. Dogs instinctively mask pain and illness, which is why watching appetite, bathroom habits, and energy levels matters more than waiting for an obvious symptom.
Is it normal for my dog to skip one meal?
Usually, yes. One missed meal in an otherwise well dog isn’t typically a concern. It becomes worth a call if it continues into a second day or comes with other changes.
What’s the single fastest sign something’s seriously wrong?
A swollen or bloated stomach, especially with retching and restlessness. That combination points to bloat, which is a genuine emergency.
Should I wait to see if symptoms go away on their own?
For very mild, short-lived symptoms in a dog who’s otherwise bright and eating normally, brief home monitoring is reasonable. Anything lasting beyond 24 hours, or paired with a second symptom, should go to your vet rather than continuing to wait.
Final Thoughts
I wish someone had told me all this before that winter. Not because the signs were hidden exactly, they were just quiet, and I wasn’t looking for them.
You don’t need to turn into a worried, hovering dog owner to catch this stuff early. You just need to know your dog’s normal, so you notice when something isn’t.
