Gaviscon- Benefits Side effects Alternative – Stomach Acid Heartburn Indigestion Gaviscon is used to treat problems such as the upset stomach, heartburn, acid reflux, and indigestion. Gaviscon is an antiacid and works best if taken in liquid form. Gaviscon works only on existing acid in the stomach. It does not prevent acid production. All drugs may cause side effects. Gaviscon may have minor side effects if taken without a doctor’s prescription like constipation, nausea, diarrhea or headache. The regular dosage of Gaviscon for adults is 2 to 4 tablets 4 times a day after meals and at bedtime or as needed. Follow with half a glass of water or other liquid. Do not swallow the tablets whole. In liquid, 1 or 2 tablespoonfuls 4 times a day after meals and at bedtime.