This post was written in cooperation with a veterinarian (Kertu Kivirand).
Sluggish
Lethargy is the most non-specific, yet most frequent indicator that a dog is not feeling well. If you also notice other symptoms, lethargy lasts for a long time or is very strong (the dog doesn't want to move at all), you should definitely contact a veterinary clinic. In the absence of other symptoms, it can be very difficult to find the cause of the problem, but if you are concerned, you can initially consult a veterinarian by phone.
Loss of appetite
An animal in a bad mood often gives up food either completely, eats less or only selects the tastiest pieces. There are fewer diseases in which there is an appetite, but there is another obstacle, which makes eating difficult or regurgitation of the pieces that have just been eaten. It is more difficult to notice diseases in which the appetite is good or even increased at the beginning, but they can also occur. Appetite should be distinguished from picky eating (snacking on food). As a rule, the so-called a fussy dog does not really starve itself, but after a while still agrees to eat and otherwise feels good.
Hiding
A previously social dog can hide in a sheltered place out of sight of its companions when it feels bad or is in pain. You can also hide the part of the body that causes pain.
Aggression, including growling, biting, nibbling
A negative reaction can also be expressed by squealing, clapping, pulling away or licking the hand. Dogs are often very good at hiding pain. If an unsuspecting painful spot is touched, the dog may suddenly react aggressively. It is a protective reaction that the dog may not even anticipate. However, dogs living with chronic pain can become mischievous if they anticipate a person approaching the painful area. More common is ear pain, which the owner may not be aware of, but the person (often a child) who has been scratched by the dog may be bitten. Chronic pain makes the body hypersensitive to all other pain and touch, causing an exaggerated response. Unexpected aggression can also occur in neurological diseases, such as brain tumor or epilepsy. With hearing or vision loss, dogs may become frightened because they did not notice a person or another animal. In the case of an adult dog showing aggression for the first time, it is worth looking for another root cause.
More frequent or less frequent defecation/urinating, difficulty in taking a position, defecation/urinating in an inappropriate place
Frequent defecation occurs in case of diarrhea, and the consistency of the stool should also be monitored. If defecation becomes less frequent or stops altogether and/or the action is strained, painful, it may be constipation or intestinal obstruction. Frequent urination also occurs in diseases of the urinary tract and many other organs. It is also worth monitoring the amount of urine, whether there is leakage of urine and other suspicious things. Problems with positioning may indicate pain, an orthopedic or neurological problem. Older dogs with cognitive dysfunction may forget they just went outside or become confused and defecate/urinate in the wrong place.
Disturbances in balance, including circling, head tilt, falling, swaying gait
These symptoms can occur with ear problems or neurological diseases. Movement problems, including limping, hunched over, reluctance to run, jump or move at all, stiffness after lying down, physical exertion or rising, slower movement indicate orthopedic disease. Almost all old dogs have chronic joint diseases that develop stealthily over a long period of time and are therefore imperceptible. An older dog who is simply not as energetic as when he was young may actually be suffering from severe chronic pain that is being skillfully hidden. Dogs visibly limp only when the pain is already quite strong or normal use of the limb is not possible. Poor eyesight also makes movement cautious and slow. A dog with poor hearing may not be able to move because it cannot hear interesting sounds or the owner's commands.
Blowing while resting
Blowing and breathing faster during physical exertion, in an anxious situation, in a hot climate is normal. However, if panting occurs, for example, when lying down, with very light exertion or for no apparent reason, it is worth checking the dog's respiratory tract and heart. Rapid fatigue can indicate respiratory or heart diseases, as well as obesity, endocrine diseases, orthopedic problems.
Changes in sleep rhythm
A change in the times or duration of naps can indicate cognitive dysfunction or the development of dementia/senility in an older dog. Chronic stress, for example due to pain, also causes changes in sleep rhythms.
Restlessness, clinging, trembling
Some dogs signal discomfort or pain by looking for more company instead of hiding. Restlessness can manifest itself in aimless movement, constant searching for a place, nibbling, scratching, walking in and out, as well as frequent licking/chewing of oneself (up to the appearance of skin lesions).
Voicing
Dogs do not often use whining, whining, or barking to signal their concerns, so you cannot rely on a sick dog to vocalize its bad mood. The concern can be quite big if the dog also uses his voice to complain. If changes in behavior are difficult to notice and come and go, keeping a diary can be helpful. Write down what you noticed and whether you can also relate the change to some factor. A dog's body language signals pain long before other behavioral changes. In addition, observe facial expressions and the position of the ears. It is worth paying attention to your dog's normal body language, and you can also find visual material on the Internet about signs of pain (for example, the AAHA instructions https://www.aaha.org/globalassets/02-guidelines/pain-management/painmanagement_dogs_web.pdf).