Does Gaviscon Have Any Negative Side Effects?

October 9, 2025 •

4 min read

Gaviscon is a widely used over-the-counter medication for heartburn and acid indigestion, and for most people, it is considered very safe. However, like any medication, it does have potential negative side effects, though they are often mild and infrequent.

Quick Summary

Gaviscon can cause mild side effects such as constipation or diarrhea, depending on the specific formulation. Rare, but more serious, reactions can occur, including allergic responses and complications with long-term use, especially for those with pre-existing conditions like kidney disease. Drug interactions are also a consideration.

Key Points

Common Side Effects: Mild gastrointestinal issues like constipation (from aluminum) and diarrhea (from magnesium) are the most frequent side effects.
Serious Allergic Reactions: Though rare, severe allergic reactions involving hives, swelling of the face or throat, and difficulty breathing require immediate medical attention.
Risks with Long-Term Use: Prolonged use, especially in those with kidney disease, carries risks of aluminum accumulation and mineral imbalances like hypophosphatemia.
Drug Interactions: Gaviscon can affect the absorption of other medications, including certain antibiotics, iron supplements, and levothyroxine, necessitating a two-hour separation of doses.
Importance of Medical Consultation: If symptoms persist for more than two weeks, or if you have pre-existing health conditions, consult a healthcare provider to ensure safe use and rule out more serious issues.

Gaviscon is a common over-the-counter medication designed to combat the discomfort of acid reflux and indigestion. Its unique dual-action formula not only helps neutralize stomach acid but also creates a physical barrier, or 'raft', on top of stomach contents to prevent acid from splashing back into the esophagus. The medication's core ingredients often include a combination of alginic acid, sodium bicarbonate, and either magnesium carbonate or aluminum hydroxide, depending on the specific product. While effective for many, it is important to be aware of the potential negative side effects, ranging from common, mild gastrointestinal disturbances to rare, more serious complications associated with long-term use.

Common Side Effects of Gaviscon

For the vast majority of users, Gaviscon is well-tolerated, and side effects are either nonexistent or mild. The most frequently reported issues are linked to the antacid components designed to neutralize stomach acid.

Constipation: Some formulations of Gaviscon contain aluminum hydroxide, which can cause or worsen constipation. This is a common side effect of aluminum-based antacids and is often balanced with a magnesium component.
Diarrhea: Conversely, the magnesium-based ingredients (like magnesium carbonate or magnesium trisilicate) included in some Gaviscon products can lead to a laxative effect, causing diarrhea. Brands often combine aluminum and magnesium to balance these opposing effects, but one may still dominate.
Other Mild Gastrointestinal Issues: Less commonly, individuals may experience other digestive discomforts, such as nausea, mild stomach cramps, bloating, or belching. An altered sense of taste has also been reported in some instances.

Rare and Serious Side Effects

While very rare, more severe side effects and adverse reactions are possible, especially in sensitive individuals or those with underlying health conditions. It is crucial to be aware of these and to seek immediate medical help if they occur.

Severe Allergic Reactions: A severe allergic reaction, known as anaphylaxis, is a medical emergency. Signs can include hives, difficulty breathing, wheezing, or swelling of the face, lips, tongue, or throat.
High Magnesium Levels (Hypermagnesemia): In individuals with impaired kidney function, magnesium from the antacid component can accumulate to toxic levels. This condition, hypermagnesemia, can cause symptoms like confusion, drowsiness, muscle weakness, and a fast or irregular heartbeat.
Kidney Problems: For those with pre-existing kidney disease, long-term use can increase the risk of aluminum accumulation and related complications. Symptoms of worsening kidney issues include swelling in the ankles or feet, or a change in urination.

Long-Term Use and Chronic Risks

Occasional use of Gaviscon is generally safe, but chronic, long-term use presents additional risks, particularly for those with certain medical conditions.

Phosphorus Depletion (Hypophosphatemia): Long-term, high-dose use of aluminum-containing antacids can bind to dietary phosphate in the gut, leading to low phosphate levels in the blood. Severe, chronic hypophosphatemia can cause muscle weakness, bone pain, and even lead to a condition called osteomalacia.
Aluminum Accumulation and Toxicity: In patients with renal failure, aluminum can accumulate in the body over time. This can deposit in bone, joints, and the brain, potentially leading to osteomalacia or even neurological issues like encephalopathy, which is characterized by speech disorders, seizures, and coma.
Masking Serious Conditions: Continuous reliance on antacids for recurring symptoms may mask a more serious underlying condition, such as GERD, peptic ulcers, or even certain cancers. Persistent symptoms after more than two weeks of use should prompt a visit to a doctor.

Potential Drug Interactions with Gaviscon

Gaviscon can interfere with the absorption and effectiveness of other medications. It is recommended to separate the dose of Gaviscon by at least two hours from other drugs.

Commonly Affected Medications:

Certain antibiotics (e.g., tetracyclines, quinolones)
Iron supplements
Levothyroxine (for thyroid disorders)
Bisphosphonates (for bone conditions)
Some heart medications, like digoxin
Painkillers like ibuprofen and aspirin (note: Gaviscon is generally safe with paracetamol)

Comparison of Antacid Side Effects


Feature	Gaviscon	Tums (Calcium Carbonate)	Maalox/Mylanta (Magnesium Hydroxide/Aluminum Hydroxide)
Mechanism of Action	Forms a floating barrier ('raft') and neutralizes acid.	Directly neutralizes stomach acid.	Directly neutralizes stomach acid.
Primary Active Ingredients	Alginic acid + magnesium carbonate / aluminum hydroxide.	Calcium carbonate.	Magnesium hydroxide + aluminum hydroxide.
Common Side Effect Profile	Constipation or diarrhea, depending on formula's balance.	Constipation, belching, bloating.	Constipation (from aluminum) or diarrhea (from magnesium).
Notable Differences	Barrier action is key for preventing acid reflux.	Can interact with medications; high calcium intake can be a concern with chronic use.	Combines ingredients to counteract side effects; balancing act may vary.

When to Consult a Healthcare Provider

While Gaviscon is largely safe for temporary use, a consultation with a doctor or pharmacist is advised if any of the following apply:

You have taken Gaviscon regularly for more than 7 days and symptoms persist.
You experience severe or persistent side effects, such as severe stomach pain, constipation, or diarrhea.
You have a pre-existing medical condition, especially kidney disease, liver disease, or heart disease.
You are on a sodium-restricted or magnesium-restricted diet.
You are taking other medications, particularly those known to interact with antacids.
You notice signs of an allergic reaction or other serious side effects.
For long-term users, it's advisable to talk to a doctor before stopping abruptly, as symptoms might return.

In conclusion, Gaviscon is a safe and effective treatment for occasional heartburn and indigestion for most people, leveraging its unique raft-forming action and antacid properties. However, users should be mindful of potential side effects, particularly gastrointestinal issues like constipation and diarrhea, which depend on the product's specific formulation. Those with kidney disease or other chronic conditions must be especially cautious, as long-term use can lead to more serious risks like mineral imbalances and aluminum accumulation. Furthermore, a number of important drug interactions exist, and Gaviscon should be taken separately from many other medications. For prolonged symptoms or any concerns about side effects or interactions, speaking with a healthcare professional is the safest course of action.

Frequently Asked Questions

The most common side effects are mild gastrointestinal issues, specifically constipation from aluminum-based formulations and diarrhea from magnesium-based ones. The specific side effect depends on the particular Gaviscon product used.

Yes, although it is rare, severe side effects can occur. These include allergic reactions like anaphylaxis (hives, swelling, difficulty breathing) and, in people with kidney disease, elevated magnesium levels (hypermagnesemia) or aluminum toxicity with long-term use.

Gaviscon is not generally recommended for long-term use without a doctor's supervision. Chronic, excessive use can lead to complications such as hypophosphatemia, especially with aluminum-containing formulas. It may also mask symptoms of more serious underlying conditions.

Gaviscon can reduce the absorption of certain medications, including some antibiotics, iron supplements, and thyroid medication. It is recommended to take Gaviscon at least two hours before or after other medications to avoid interactions.

Individuals with certain conditions should consult a doctor before use, including those with kidney disease, liver disease, or heart disease. People on a sodium-restricted diet or those with phenylketonuria may also need to avoid certain formulations.

Signs of an allergic reaction include skin rash, itching, hives, and swelling of the face, tongue, or throat. Get immediate medical help if you experience these symptoms.

If you have taken Gaviscon for more than seven days and your symptoms have not improved or have worsened, you should consult a healthcare professional. Persistent or worsening symptoms could indicate a more serious condition requiring different treatment.