According to About Doggies, dogs can eat TUMS for an upset stomach. The site recommends unflavored TUMS as opposed to TUMS with flavor; the added flavoring chemicals are unhealthy for dogs. About Doggies recommends the liquid form of TUMS over the tablet form to avoid a choking hazard.
While TUMS can be used to soothe a dog’s gas, the gas could be a sign of a major ailment, such as gastric torsion. The website emphasizes the need to have a veterinarian determine if gas is a symptom of something serious. TUMS don't cure any ailment and may mask an underlying issue that requires early diagnosis and treatment.