3f339d4d_Gerbil_Care__It_might_be___
[My Gerbil...] has diarrhea [It might be...] 
unless you have recently given him or her a lot of unusual foods or veggies, diarrhea is a serious symptom which could affect your own health (more...). See the vet. If you cannot see the vet immediately, start emergency ornicycline treatment. You might want to provide a warm corner with a heat lamp or reptile heater for comfort. Heat only one part of the tank so s/he can choose a comfy spot. Wash hands thoroughly after handling the gerbil, its bedding or anything in/around the tank, including the lid. If you have more than one tank, isolate the tank with the sick gerbil from the other tanks, but do not remove his/her cagemates until after you talk with the vet. (They may need treatment too.)
Gerbil Care
It might be...