By Debbie Ducommun
Lethargy in rats is a serious symptom that needs immediate attention. Give your rat a full exam to look for other signs, especially dehydration and lumps in the abdomen. Even if your rat is not dehydrated, he might have low blood sugar or an electrolyte imbalance. Try to get him to drink some juice, a sports drink, or sugar water with a pinch of salt. If your rat is dehydrated, try to get him to drink 1-2 ounces. If he refuses to drink, warmed saline solution for injections must be given under the skin.
One rare cause of lethargy is pesticide poisoning. This will also cause the pupils to be constricted so they do not expand in the dark. If your home has recently been sprayed with pesticides you’ll need to rush your rat to the vet for an injection of atropine.
If the sugary drink does not cause your rat to improve within 30 minutes, it is very important that your rat be treated with amoxicillin ASAP. One of the main causes of lethargy in rats is a secondary bacterial infection. Mycoplasma is the primary bacterial infection in most rats but does not usually cause symptoms of lethargy. In my experience (of over 23 years) the best treatment for secondary infections in rats is amoxicillin. Baytril, which most vets prescribe for rats, is not as effective for most cases of secondary infection in rats, and doxycycline, which can be quite effective in treating mycoplasma, is absolutely not effective for secondary infections. I know of many cases of rats who seemed to be dying who recovered within just a day or two of treatment with amoxicillin, while I also know of many cases of rats who died within 12-24 hours of exhibiting lethargy that went untreated. For this reason, I recommend that all rat owners have amoxicillin capsules on hand. For more information on using amoxicillin see
Another possible cause of lethargy is heat stroke. See more info in the Heat Stroke article.