Can Gaviscon Give You Diarrhea? A Deep Dive into Its Side Effects

October 12, 2025 •

4 min read

Antacids containing magnesium are a common cause of medication-induced diarrhea [1.2.8]. While generally safe, this raises the question for many users: Can Gaviscon give you diarrhea? The answer lies in its specific formulation and how its active ingredients interact with your digestive system [1.3.1].

Quick Summary

Gaviscon can cause diarrhea, typically due to the laxative effect of its magnesium-based ingredients. This article examines how Gaviscon works, the science behind its side effects, and how to manage them.

Key Points

Diarrhea is a known side effect: Gaviscon can cause diarrhea, primarily because of magnesium-based ingredients like magnesium carbonate, which have a laxative effect [1.3.2, 1.2.1].
Ingredient Balancing Act: Gaviscon often combines magnesium (which can cause diarrhea) with aluminum hydroxide (which can cause constipation) to balance the effects [1.2.2].
Magnesium is the Culprit: Magnesium salts draw water into the intestines, which softens stool and can lead to diarrhea [1.5.1]. In combined antacids, this effect can sometimes dominate [1.7.6].
Side Effects are Usually Mild: For most people, side effects from Gaviscon are uncommon and mild. If they occur, they typically resolve after stopping the medication [1.2.3].
Formulation Matters: Different Gaviscon products have different ingredients. If you experience diarrhea, a formulation without magnesium may be a better choice [1.2.8].
Opposite Effect is Possible: Due to the aluminum hydroxide content, some users might experience constipation instead of diarrhea [1.6.5].
Consult a Professional: If diarrhea or other side effects are persistent or bothersome, or if you need to use Gaviscon for more than two weeks, consult a doctor or pharmacist [1.2.1, 1.2.3].

Understanding Gaviscon: More Than Just an Antacid

Gaviscon is a popular over-the-counter medication used to relieve symptoms of heartburn, acid indigestion, and sour stomach [1.3.1]. Its primary function is twofold. First, like other antacids, it contains ingredients that neutralize excess stomach acid, providing quick relief from the burning sensation associated with acid reflux [1.4.1]. Second, and what makes Gaviscon unique, is its inclusion of alginic acid (or sodium alginate). When this ingredient comes into contact with stomach acid, it forms a viscous foam barrier, or "raft," that floats on top of the stomach contents. This physical barrier helps prevent stomach acid from splashing back up into the esophagus, addressing the root cause of reflux symptoms [1.4.1].

The active ingredients responsible for neutralizing acid often include aluminum hydroxide and a magnesium salt, such as magnesium carbonate or magnesium trisilicate [1.4.1, 1.4.4]. It is the interplay of these specific ingredients that determines the potential for gastrointestinal side effects.

The Core Question: Can Gaviscon Give You Diarrhea?

Yes, Gaviscon can cause diarrhea [1.2.4]. This side effect is primarily linked to the magnesium compounds present in many of its formulations, such as magnesium carbonate [1.3.2]. Magnesium salts have a well-known osmotic laxative effect; they work by drawing water into the intestines [1.5.1]. This increase in water softens the stool and stimulates bowel movements, which, in sufficient amounts, can lead to diarrhea [1.5.1].

Interestingly, antacid manufacturers often combine magnesium with aluminum hydroxide for a specific reason. Aluminum hydroxide, on its own, has the opposite effect and is known to cause constipation [1.6.5, 1.6.7]. The intention behind combining these two ingredients is to balance out their opposing effects on the gut, aiming for a neutral impact on bowel habits [1.2.2]. However, this balance is not always perfect. In many combination products, the diarrheal effect of magnesium tends to dominate [1.3.2, 1.7.6]. Therefore, even in a balanced formula, some individuals may be more susceptible to the laxative effects and experience diarrhea.

According to the NHS, while most people who take Gaviscon experience no side effects, if they do occur, they are likely to be mild [1.2.3]. Diarrhea, constipation, and nausea are listed as potential, though uncommon, side effects [1.2.3, 1.2.7].

Other Potential Side Effects of Gaviscon

While diarrhea is a key concern, it's not the only potential side effect. Due to the presence of aluminum hydroxide, some users may experience the opposite problem: constipation [1.2.1]. Other less serious side effects can include mild stomach cramps, nausea, or an altered sense of taste [1.2.2].

Serious side effects are very rare but can include symptoms of a severe allergic reaction, such as a rash, itching, difficulty breathing, or swelling of the face, tongue, or throat [1.4.5]. Long-term use of antacids containing aluminum, especially in high doses or in individuals with kidney disease, can lead to more significant issues like phosphate depletion and, in rare cases, aluminum toxicity [1.4.3, 1.6.2]. It is crucial to use Gaviscon as directed and not exceed the maximum recommended dose [1.4.6].

Comparing Gaviscon Formulations

Different versions of Gaviscon have varying ingredient profiles, which can influence their potential for side effects. The key is the ratio of magnesium to aluminum.


Feature	Gaviscon with Aluminum & Magnesium	Gaviscon with Only Aluminum	Gaviscon Advance (Potassium Bicarbonate)
Primary Antacids	Aluminum Hydroxide, Magnesium Carbonate [1.4.6]	Aluminum Hydroxide	Calcium Carbonate, Potassium Bicarbonate [1.2.7]
Diarrhea Potential	Moderate: Magnesium has a laxative effect [1.2.1].	Low: Primarily associated with constipation [1.6.4].	Low to None: Lacks magnesium salts known for causing diarrhea.
Constipation Potential	Moderate: Aluminum can be constipating [1.6.5].	High: The primary side effect of aluminum hydroxide [1.6.5].	Low: Not a common side effect.
Best For	Individuals seeking a balanced formula who are not prone to either diarrhea or constipation.	Individuals who tend to experience diarrhea with magnesium-based antacids.	Individuals sensitive to magnesium or aluminum, or those needing a sodium-free option.

Managing Side Effects and When to See a Doctor

If you experience mild diarrhea while taking Gaviscon, it may resolve on its own as your body adjusts. Here are a few steps you can take:

Ensure Proper Dosage: First, confirm you are not taking more than the recommended dose [1.2.1].
Stay Hydrated: If you have diarrhea, it's important to drink plenty of fluids to prevent dehydration [1.5.1].
Consider a Different Formulation: If the problem persists, talk to a pharmacist about switching to a Gaviscon formula that does not contain magnesium or has a lower amount [1.2.8].

According to medical advice, you should stop taking Gaviscon and consult a healthcare provider if your symptoms persist for more than two weeks [1.2.1]. You should also seek medical help if the side effects bother you, do not go away, or if you experience any serious symptoms like bone pain, loss of appetite, or signs of an allergic reaction [1.2.3, 1.4.7].

Conclusion: A Balanced Perspective

So, can Gaviscon give you diarrhea? Yes, it is a possible, though generally mild, side effect, primarily due to the laxative properties of its magnesium-based ingredients [1.3.2]. The combination with aluminum hydroxide is designed to mitigate this, but individuals can react differently. Most people use Gaviscon without any issues, but for those who do experience digestive upset, understanding the role of each ingredient is key to finding a solution [1.2.3]. Always adhere to the product's dosage instructions and consult with a pharmacist or doctor if you have persistent concerns or are managing other health conditions, particularly kidney disease [1.4.6].

For further reading on medication side effects, one authoritative resource is the NHS page on Gaviscon.

Frequently Asked Questions

Gaviscon can cause diarrhea because many formulations contain magnesium carbonate or other magnesium salts. Magnesium has a natural laxative effect because it draws more water into your bowels [1.5.1, 1.3.2].

No, it is not considered a common side effect. While possible, most people who take Gaviscon do not experience any side effects. When they do occur, they are typically mild [1.2.3].

If you experience mild diarrhea, ensure you are not exceeding the recommended dose and stay hydrated. If it persists or is severe, stop taking the medication and consult your doctor or pharmacist [1.2.1, 1.2.3].

Yes. Gaviscon products contain aluminum hydroxide, which is known to cause constipation. The medication combines aluminum and magnesium to try to balance these effects, but some people may be more sensitive to the constipating effect of aluminum [1.6.5, 1.2.1].

No. The potential to cause diarrhea depends on the ingredients. Formulations containing magnesium are more likely to cause it [1.7.7]. Check the label; some versions, like those relying solely on aluminum or other active ingredients, are less likely to have this effect [1.2.8].

Any mild diarrhea caused by Gaviscon should stop when you stop taking the medicine [1.2.3]. If it continues for more than a day or two after discontinuing use, you should contact a healthcare provider.

You should ask a doctor or pharmacist before using Gaviscon if you have kidney disease. Your body may not be able to clear the magnesium and aluminum properly, which can lead to accumulation and toxicity [1.4.6, 1.4.4].