Physical signs that warrant a vet call
Dogs cannot describe how they feel, so owners have to read physical cues. Some changes are obvious; others are easy to dismiss as a bad day. The following symptoms are worth acting on regardless of how minor they seem at first.
Digestive changes
Vomiting once after eating grass is common and usually harmless. Vomiting more than twice in a 24-hour window, vomiting blood, or vomiting alongside visible abdominal swelling requires same-day veterinary attention. Diarrhea that contains blood or persists beyond 48 hours also warrants a call. Constipation lasting more than two days, or repeated straining without producing stool, can indicate a blockage or other serious issue.
Changes in appetite and weight
A dog that refuses two consecutive meals has crossed a threshold worth noting. Sudden weight loss over one to two weeks, even with normal eating, can signal metabolic disease, parasites, or cancer. Weight gain paired with lethargy and thinning coat sometimes points to hypothyroidism.
Respiratory and cardiovascular signs
Labored breathing, persistent coughing, or a cough that sounds wet or honking at night can reflect heart disease, pneumonia, or tracheal problems. Pale, blue, or white gums are an emergency: call a veterinarian immediately. Normal gum color is a healthy pink.
Skin, coat, and eyes
Excessive scratching, hair loss in patches, or skin that is red and inflamed between the toes or along the belly can indicate allergies, infection, or mange. Cloudy eyes, yellow or green discharge, or persistent squinting may signal infection or injury. Compare what you observe with what a healthy coat and eyes look like to calibrate your baseline.
Behavioral signs that often go unnoticed
Behavior shifts are frequently the first warning a dog sends. Because changes happen gradually, they are easy to rationalize or overlook.
Lethargy and withdrawal
A dog that sleeps more than usual, refuses walks it normally enjoys, or isolates itself in another room may be in pain or fighting illness. One quiet day is not alarming. Two or more days of reduced activity, especially combined with any physical symptom, is a reason to call your vet.
Sudden aggression or irritability
A normally social dog that growls when touched in a specific spot is often communicating pain. Do not punish this behavior. Instead, note where the dog reacts and report it to your veterinarian. Chronic stress can also produce irritability and digestive upset, as described in the physical effects of anxiety in pets.
Excessive drinking or urinating
Polydipsia (increased thirst) and polyuria (increased urination) together are classic signs of diabetes, Cushing's disease, or kidney disease in dogs. If your dog is emptying its water bowl more than usual or having accidents indoors after being reliably house-trained, those changes should be documented and reported.
Polydipsia
Abnormally increased thirst. In dogs, it is often measured as drinking more than 100 ml of water per kilogram of body weight per day and can signal kidney disease, diabetes, or hormonal disorders.
Polyuria
Abnormally increased urination, often paired with polydipsia. A dog producing much larger or more frequent volumes of urine than usual should be evaluated by a veterinarian.
Lethargy
A state of unusual tiredness, low energy, or reduced responsiveness. In dogs, lethargy that persists beyond one day or accompanies other symptoms is considered clinically significant.
Hypothyroidism
A condition in which the thyroid gland produces too little hormone. Common signs in dogs include weight gain, thinning coat, and lethargy, and it is diagnosed with a blood test.
Deciding how quickly to act
Not every symptom is an emergency, but some are. Difficulty breathing, collapse, uncontrolled bleeding, suspected ingestion of a toxin, or seizures require an emergency clinic right away. Symptoms that are new, worsening, or involve multiple body systems at once generally warrant same-day contact with your regular vet rather than a wait-and-see approach.
For a structured breakdown of which situations require an ER visit versus a scheduled appointment, see when a sick pet needs the ER versus a regular vet visit.
When in doubt, call your veterinarian and describe what you are observing. Most practices can advise over the phone whether to come in immediately, schedule an appointment, or monitor at home. Keeping a written note of symptoms with dates and duration helps the veterinarian assess the situation more accurately.
This article is for informational purposes only and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian with concerns about your dog's health.