I took some tums (calcium carbonate) for stomach acid, but instead it gives me gas and stomach ache, why would it cause the two?

May not be acid: The differential causes of abdominal pain are multiple - you are self diagnosing stomach acid - ? Other causes such as heart disease, esophageal spasm, or maybe Tums (calcium carbonate) aren't adequate to control the acid if that is the cause. Try otc Omeprazole 20mg am and pm - if this relieves the symptoms then stomach acid is a likely diagnosis. Would recommend a visit to your primary care physician at any rate.

It doesn't: This is a simple antacid and calcium in a form that is easily absorbed & used in your bones. It doesn't cause gas or a stomach ache. You likely have an unrelated problem that Tums does not treat. Tums is sometimes taken as a simple calcium supplement.