Sick hamsters usually exhibit the following symptoms, and a comprehensive judgment should be made based on changes in their appearance, behavior, and physiology:

I. Abnormal Appearance
Hair Condition
Rough, dull fur, with partial or extensive hair loss (may be due to skin diseases or parasitic infections).
Damp, sticky fur around the tail or anus (a typical sign of wet tail disease).
Abnormalities of the Five Senses
Eyes: Redness, swelling, and increased discharge (eye boogers or tear stains); in severe cases, inability to open the eyes.
Nose: Runny nose and dirty fur around the nose (cold or respiratory infection).
Ears: Accumulated earwax and foul odor (ear inflammation or infection).
Teeth: Overgrown teeth leading to drooling and difficulty eating.
Body Changes
Sudden weight loss or localized hard lumps (may be tumors).
Skin redness, ulcers, or scabs (fungal or bacterial infections).
II. Abnormal Behavior
Decreased Activity
Huddling in corners for long periods, slow response, and avoiding interaction.
Significantly reduced or even complete cessation of running wheel use.
Abnormal Eating Habits
Loss of appetite or refusal to eat, accompanied by rapid weight loss.
Frequent trips to the toilet (diarrhea or urinary system problems).
Abnormal Movements
Frantically digging at the cage and rapid breathing when suffering from heatstroke.
Circling or convulsions may occur due to brain diseases.
III. Abnormal Physiological Indicators
Breathing: Shallow, rapid, or labored breathing (pneumonia or heart disease).
Body Temperature: Hot body when suffering from heatstroke; gradually cooling body when near death.
Excrement: Soft or loose stools (gastroenteritis or wet tail disease).
IV. Emergency Symptoms (Immediate Veterinary Care Required)
Protruding eyeballs (may be tumors or infections).
Apparent death (caused by low temperature; emergency warming is needed).
Persistent convulsions or inability to stand (nervous system diseases).
If any of the above symptoms are observed, it is recommended to first isolate the sick hamster, adjust the environment (e.g., maintain a stable temperature, clean the bedding), and consult a veterinarian as soon as possible.