Side effects from sodium bicarbonate or baking soda include bloating, nausea and intestinal gas, according to WebMD. More serious but rare side effects include swelling of the hands, ankles or feet and unusual weight gain. When taken with a diet heavy in calcium, sodium bicarbonate can cause milk-alkali syndrome. This causes a shift in the body's alkaline-base balance, which can result in impaired kidney function, according to Medline Plus.
Baking soda is an antacid prescribed to reduce heartburn and acid indigestion, according to Medline Plus. It's also prescribed to make the blood or urine less acidic. Because it is an antacid, baking soda can reduce the effectiveness of certain drugs that require stomach acid to work, such as ampicillin, atazanavir, certain anti-fungal medications, iron supplements, pazopanib and sucralfate. Drug interactions with baking soda can occur with aspirin or other salicylates, barbituates such as phenobarbital, calcium supplements, corticosteroids such as prednisone, medications with a special (enteric) coating to protect the stomach, lithium, quinidine and water pills or diuretics such as hydrochlorothiazide. Patients should tell their doctors about any medications they are taking as well as any past history of stomach bleeding, congestive heart failure, high blood pressure or kidney disease, advises Medline Plus. Because this medication increases the amount of sodium in the body, patients on low-sodium diets should check with their doctor before using it.