Dogs don’t have the power of speech like humans do. This is why, when they get sick, they need to show us owners they’re hurting in other ways. While some illnesses have tell-tale signs like physical symptoms, others manifest in more silent ways, such as a change in behavior.

Pet parents who know their dogs very well will be able to notice behavioral changes faster, but some of the most common behavior changes related to dog sickness are still pretty easy to spot. It’s important to keep a close eye on your pet to notice when these changes occur. If something feels off about your pet, you should take it in to see a veterinarian and get a diagnosis—there’s a chance that the behavior change is indicative of an underlying health issue.

Here are seven of the most common behavioral changes that pet parents see when their dogs are ill.

1. Hiding: If your dog is typically social and anxiety-free, it can be concerning to never see it out and about. Friendly, social dogs will normally hang out where people are in the home, but sick dogs may begin to hide under beds, in closets or in other confined spaces. This is usually to do with your dog’s fear of being hurt more if it is injured or its desire to rest and heal away from stress.
2. Aggressive behavior: Dog owners usually have a firm grasp on their dog’s temperament around family members or strangers, which is why sudden aggression can be alarming. If you dog goes from a happy, carefree pup one day to an irritable, snapping animal the next, this should be a red flag. Try to identify if there was any external cause for your dog’s aggression first. If the aggressive behavior lasts longer than a day with no cause to be found, you should consider taking it to a vet.
3. Lethargy or excessive sleepiness: Dogs can get really lazy at times and spend the entire afternoon laying around or sleeping. Sometimes, this is warranted, such as after a long workout or playdate. However, if your dog is usually active and suddenly begins walking around or playing a lot less than it used to, or if it suddenly starts sleeping most of the day, it might be tired from fighting an illness you can’t see.
4. Changes in appetite: Your dog’s appetite should mostly stay the same day over day. While some dogs won’t have much of an appetite some days or will feel famished after working hard on a run, longer-term changes in appetite can be indicative of a problem. If your pup refuses to eat, it might be suffering from a disease or GI tract issue. Underfed dogs can lose excessive weight and get even more sick. Similarly, if your dog goes from eating one cup of food per meal to suddenly wanting more and more, it might have a disease or worms changing its appetite. The same goes for water intake—if your dog is suddenly lapping up water constantly, a health problem may be to blame.
5. Potty problems: Problems urinating or defecating can be clear signs that your dog is suffering from an illness. One of the most obvious signs pet parents notice is when their dog goes inside the house, rather than outside. If your dog is peeing inside, you’ll want to determine whether it’s marking, peeing out of defiance or if it seems to be an accident. Other signs include difficulty using the bathroom or straining to go.
6. Increased vocalizations: While dogs obviously lack the power of speech, that doesn’t mean they don’t try to talk to us once in a while. When dogs get sick, they may begin vocalizing much more than you are used to. This may be in the form of barking, whining, whimpering or “talking". Whining and whimpering are most likely signs of illness, since they indicate distress, fear and pain.
7. Changes in mood: Dogs can think and feel things similar to humans, which means they might not always act like themselves. However, if your dog begins acting strangely all day, every day, something might be really wrong with its health. For example, a normally independent dog might become extremely clingy and distressed when not given attention, while a cuddly, sweet dog might act irritable or defiant and will not want to be touched at all.

Pinpoint the changes

The only way you can accurately identify these behavioral changes in your dog is if you know it well enough to understand what is normal. While some behavior changes are merely signs of anxiety or stress, like a suddenly clingy dog, or signs your dog is growing, like changes in appetite, it’s important to maintain a keen eye on your pooch to make sure you’re catching illnesses or injuries early and get your pup the help it needs.