It’s not likely to be, Danielle. If you follow label directions, most toilet bowl cleaning tablets would not be expected to cause problems beyond minor stomach upset, should a dog take a drink out of the diluted water in the toilet bowl. Bacterial-related gastrointestinal problems could occur from drinking stagnant toilet water, however, so it is still a good idea to discourage your dog from imbibing from the commode.
How dangerous is it for a dog to take a drink from a toilet bowl treated with a cleaning tablet?
It really depends, Hannah. Most toilet bowl cleaning tablets that are used according to label directions would not be expected to cause serious or systemic clinical problems, provided that the animal does not ingest the tablet directly. Typically, we see only mild gastrointestinal upset. If you feel that your dog may have come into contact with more of the cleaner than would normally be present in the toilet bowl, we advise that you contact your local veterinarian, emergency clinic or the ASPCA Animal Poison Control Center at (888) 426-4435.