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Rennie Liquid Heartburn Relief - 250ml

Rennie Liquid Heartburn Relief - 250ml

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  • ✔️ Neutralises excess stomach acid for fast heartburn relief
  • ✔️ Alginate raft physically prevents acid refluxing into the oesophagus
  • ✔️ Liquid format ideal for those who struggle with tablets
  • ✔️ Suitable for heartburn in pregnancy — always consult your healthcare provider
  • ✔️ Relieves acid indigestion and dyspepsia after meals and at bedtime

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What Is Rennie Liquid Heartburn Relief?

 

If you've ever felt that uncomfortable burning sensation creeping up your chest after a meal, you'll know how disruptive heartburn can be. Rennie liquid heartburn relief is an over-the-counter oral antacid suspension designed to neutralise excess stomach acid and provide fast, soothing relief from heartburn, acid indigestion, and dyspepsia. Available in a 250ml bottle, it's a practical option for those who find tablets difficult to swallow or simply prefer a liquid format. You can browse the full range of indigestion treatments at Cured Pharmacy if you'd like to compare your options.

Heartburn is extremely common in the UK. The NHS estimates that around one in five people experience it regularly, and it can affect anyone — from those who've eaten a particularly rich meal to pregnant women dealing with it daily. Rennie Liquid contains a combination of calcium carbonate, sodium alginate, and sodium bicarbonate, working together to tackle the root cause of that burning discomfort.

 

How Does Rennie Liquid Heartburn Relief Work?

 

The mechanism behind Rennie Liquid is straightforward but effective. It works in two complementary ways to address both the acid itself and the physical reflux of that acid into the oesophagus.

  • Acid neutralisation: Calcium carbonate and sodium bicarbonate react with hydrochloric acid in the stomach, raising the gastric pH and reducing the corrosive effect of excess acid on the oesophageal lining.
  • Raft formation: Sodium alginate, derived from seaweed, reacts with stomach acid to form a viscous gel raft that floats on top of stomach contents. This physical barrier helps prevent acid from refluxing back up into the oesophagus.
  • Symptom relief: Together, these actions soothe the burning sensation, reduce belching, and ease the discomfort associated with acid indigestion and dyspepsia.

This dual-action approach means Rennie Liquid addresses both the chemical and mechanical aspects of acid reflux, which is why many people find it particularly helpful after meals or at bedtime when symptoms tend to worsen.

 

Who Should Use Rennie Liquid Heartburn Relief?

 

Rennie Liquid is suitable for a wide range of adults and older children. It's particularly useful if you experience occasional heartburn or indigestion rather than a chronic, daily condition — though your pharmacist or GP can advise further if symptoms are frequent.

  • Adults and children aged 12 and over experiencing occasional heartburn or acid indigestion
  • Pregnant women suffering from pregnancy-related heartburn (always check with your midwife or GP first)
  • People who prefer a liquid antacid over chewable tablets
  • Those with dyspepsia triggered by food, alcohol, or lifestyle factors

It is not suitable for children under 12 years of age. If you have kidney disease, hypercalcaemia, or are on a sodium-restricted diet, speak to your pharmacist before use.

 

How Does Rennie Liquid Compare to Rennie Tablets?

 

Feature Rennie Liquid 250ml Rennie Chewable Tablets
Active ingredients Calcium carbonate, sodium alginate, sodium bicarbonate Calcium carbonate, magnesium carbonate
Raft-forming action Yes — sodium alginate forms a protective gel raft No raft-forming action
Suitable for Adults and children 12+; those preferring liquid Adults and children 12+; on-the-go use
Format Oral suspension (liquid) Chewable tablet

 

Is Rennie Liquid Suitable for Long-Term Use?

 

Rennie liquid heartburn relief is intended for short-term, symptomatic relief. It should not be used continuously for more than seven days without seeking medical advice. If your symptoms persist beyond a week, worsen, or are accompanied by difficulty swallowing, unexplained weight loss, or vomiting, you should see your GP promptly — these could indicate a more serious underlying condition such as gastro-oesophageal reflux disease (GORD) or a peptic ulcer. The NHS recommends that persistent heartburn always be investigated by a healthcare professional. If you're also managing other digestive concerns, you might find our IBS and cramps collection helpful for exploring further options.

Store Rennie Liquid below 25°C and do not freeze. Always shake the bottle well before each use and keep it out of reach of children.

This product is a medicine. Speak to your doctor or pharmacist before using if you have an underlying medical condition or are taking other medicines.

Rennie Liquid Heartburn Relief 250ml specifications
Treatment category Heartburn & Indigestion / Antacids
Mechanism of action Acid neutralisation and alginate raft formation
Effective for Heartburn, acid indigestion, dyspepsia
Suitable for Adults and children aged 12 and over
Active ingredients Calcium carbonate 500mg/5ml, Sodium alginate 250mg/5ml, Sodium bicarbonate 133.5mg/5ml
Pack size 250ml
UK classification General Sale List (GSL)
Drug class Antacid / Alginate
Preparation Oral suspension
Route of administration Oral

Specifications of Rennie Liquid Heartburn Relief 250ml

 

What Is Rennie Liquid Heartburn Relief and What Is It Used For?

 

Rennie Liquid Heartburn Relief is an oral antacid suspension used to relieve the symptoms of heartburn, acid indigestion, and dyspepsia. It contains three active ingredients — calcium carbonate, sodium alginate, and sodium bicarbonate — which work together to neutralise stomach acid and form a protective barrier against acid reflux. It is classified as a General Sale List (GSL) medicine in the UK, meaning it is available without a prescription. Rennie liquid heartburn relief is one of the most widely recognised antacid products available in UK pharmacies.

 

What Do You Need to Know Before Using Rennie Liquid Heartburn Relief?

 

Before using this medicine, it's important to check whether it is appropriate for you. Do not use Rennie Liquid if any of the following apply:

  • You are allergic to any of the active or inactive ingredients
  • You have hypercalcaemia (high calcium levels in the blood)
  • You have severe kidney impairment or renal failure
  • You are under 12 years of age
  • You have been advised to follow a low-sodium diet (this product contains sodium)
  • You have phenylketonuria — check the inactive ingredients with your pharmacist

Speak to your pharmacist or GP before using Rennie Liquid if you are pregnant, breastfeeding, or have any chronic medical condition. The NHS advises that heartburn in pregnancy is common but that any medicine use should be discussed with a healthcare professional first.

Rennie Liquid may interact with certain other medicines. Separate doses by at least two hours if you are taking any of the following:

  • Tetracycline antibiotics (e.g. doxycycline)
  • Iron supplements
  • Antifungal medicines (e.g. itraconazole, ketoconazole)
  • Some HIV medicines
  • Thyroid medicines (e.g. levothyroxine)
  • Bisphosphonates (e.g. alendronic acid)

Antacids can reduce the absorption of these medicines if taken at the same time, so timing your doses carefully is essential.

 

How Should You Use Rennie Liquid Heartburn Relief?

 

Always use this medicine exactly as described in the patient information leaflet or as directed by your pharmacist. Follow these steps each time you take a dose:

  1. Shake the bottle well before use
  2. Measure the correct dose using the measuring cup or spoon provided
  3. Take the liquid orally, after meals and at bedtime, or when symptoms occur
  4. Do not exceed the maximum daily dose
  5. Replace the cap securely after use
Indication Age Group Dose Frequency
Heartburn / acid indigestion Adults & children 12+ 10–20ml Up to 4 times daily (max 60ml/24hrs)
Not recommended Under 12 years

If you are also managing symptoms such as bloating or cramping alongside heartburn, you may find it useful to explore our IBS and cramps range for additional support options.

 

What Are the Possible Side Effects of Rennie Liquid Heartburn Relief?

 

Like all medicines, Rennie Liquid can cause side effects, although not everyone experiences them. Most side effects are mild and resolve on their own.

Common side effects (may affect up to 1 in 10 people):

  • Constipation
  • Flatulence (wind)
  • Chalky or slightly sweet aftertaste

Less common side effects (may affect up to 1 in 100 people):

  • Nausea
  • Stomach discomfort or bloating
  • Rebound acid hypersecretion with prolonged use
  • Hypercalcaemia (raised blood calcium) with excessive long-term use — symptoms include muscle weakness, confusion, or increased thirst

Stop using Rennie Liquid and seek medical advice immediately if you experience signs of an allergic reaction, such as swelling of the face, lips, or throat, difficulty breathing, or a severe skin rash. The NHS advises contacting 999 or going to A&E if you suspect a serious allergic reaction (anaphylaxis).

 

How Should You Store Rennie Liquid Heartburn Relief?

 

Correct storage helps maintain the quality and safety of the medicine. Follow these guidelines:

  • Store below 25°C in a cool, dry place
  • Do not freeze
  • Keep the bottle tightly closed when not in use
  • Keep out of the sight and reach of children
  • Do not use after the expiry date printed on the label
  • Do not dispose of medicines via wastewater or household waste — return unused medicine to your pharmacy

If you're looking for other digestive health or general wellness products, our vitamins and supplements collection includes a range of products that may support your overall gut health alongside antacid treatment.

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Your safety and success are our highest priorities. Our medical team rigorously evaluates every product and piece of advice we provide, ensuring you receive only the most effective, science-backed solutions available.

Frequently Asked Questions

Where can I buy Rennie Liquid Heartburn Relief online in the UK?

You can buy Rennie Liquid Heartburn Relief 250ml directly from Cured Pharmacy, a GPhC-registered UK online pharmacy. It is available without a prescription as an over-the-counter medicine. Simply add it to your basket and choose your preferred delivery option at checkout.

How does Rennie Liquid Heartburn Relief work in the body?

Rennie Liquid works through two mechanisms: calcium carbonate and sodium bicarbonate neutralise excess stomach acid, while sodium alginate reacts with acid to form a gel raft that floats on stomach contents and physically prevents acid from refluxing into the oesophagus. This dual action provides both chemical and mechanical relief. Most people notice symptom improvement within a few minutes of taking the correct dose.

How do I use Rennie Liquid Heartburn Relief step by step?

Shake the bottle well before each use, then measure 10–20ml using the measuring cup. Take the dose orally after meals and at bedtime, or whenever symptoms occur. Do not exceed 60ml in any 24-hour period, and always replace the cap tightly after use.

What is the correct dose of Rennie Liquid Heartburn Relief for adults?

Adults and children aged 12 and over should take 10–20ml up to four times daily, ideally after meals and at bedtime. The maximum dose is 60ml in any 24-hour period. If you find you need the maximum dose regularly, speak to your pharmacist or GP.

When is the best time to take Rennie Liquid Heartburn Relief?

The most effective times to take Rennie Liquid are after meals and at bedtime, as these are the periods when stomach acid production is highest and reflux is most likely to occur. You can also take it as soon as symptoms appear at any other time of day. Taking it on an empty stomach is less effective because the alginate raft needs stomach contents to float on.

Can I take Rennie Liquid Heartburn Relief during pregnancy?

Rennie Liquid is commonly used to relieve heartburn during pregnancy, which is a very frequent symptom, particularly in the second and third trimesters. However, you should always speak to your midwife, GP, or pharmacist before using any medicine while pregnant to confirm it is appropriate for your individual circumstances. The NHS recommends discussing all medicines with a healthcare professional during pregnancy.

Is Rennie Liquid Heartburn Relief suitable for children?

Rennie Liquid is suitable for children aged 12 and over at the same dose as adults. It is not recommended for children under 12 years of age. If your child under 12 is experiencing heartburn or indigestion symptoms, speak to your GP or pharmacist for appropriate advice and treatment options.

What are the side effects of Rennie Liquid Heartburn Relief?

Side effects are uncommon but may include constipation, flatulence, and a chalky aftertaste. Less commonly, some people experience nausea or mild stomach discomfort. If you notice any signs of an allergic reaction — such as facial swelling, difficulty breathing, or a severe rash — stop taking the medicine and seek emergency medical help immediately.

How long can I use Rennie Liquid Heartburn Relief for?

Rennie Liquid should not be used continuously for more than seven days without seeking medical advice. If your symptoms persist beyond a week, or if you experience additional symptoms such as difficulty swallowing, unexplained weight loss, or persistent vomiting, you should consult your GP. Prolonged, frequent heartburn may indicate an underlying condition such as GORD that requires further investigation.

What happens if I take too much Rennie Liquid Heartburn Relief?

Taking more than the recommended dose (more than 60ml in 24 hours) may increase the risk of side effects such as constipation or, with prolonged excessive use, raised blood calcium levels (hypercalcaemia). If you think you or someone else has taken too much, contact NHS 111 or your nearest A&E for advice. Always keep medicines out of reach of children.

Can Rennie Liquid Heartburn Relief interact with other medicines?

Yes — Rennie Liquid can reduce the absorption of certain medicines if taken at the same time. These include tetracycline antibiotics, iron supplements, antifungals such as itraconazole, bisphosphonates, levothyroxine, and some HIV medicines. To avoid this interaction, separate your dose of Rennie Liquid from these medicines by at least two hours. Always tell your pharmacist about all medicines you are taking, including over-the-counter products.

What are the alternatives to Rennie Liquid Heartburn Relief?

Common alternatives include Gaviscon Advance liquid (also alginate-based), Peptac liquid, or simple antacid tablets containing calcium carbonate or magnesium trisilicate. For more persistent symptoms, a GP may recommend a proton pump inhibitor (PPI) such as omeprazole. You can explore our full indigestion treatments collection to compare available options.

Does Rennie Liquid Heartburn Relief contain any allergens or additives?

Rennie Liquid contains inactive ingredients including sorbitol, saccharin sodium, and various flavouring agents — always check the full patient information leaflet if you have known sensitivities. It does not contain gluten, but it does contain sodium, which is relevant if you are on a sodium-restricted diet. If you are unsure whether this product is suitable for you, speak to your pharmacist before use.

Can I take Rennie Liquid Heartburn Relief with food or drink?

Rennie Liquid is actually most effective when taken after meals rather than on an empty stomach, as the alginate raft needs stomach contents to form properly and float effectively. Avoid taking it with large amounts of milk, as this can temporarily increase acid production. Lifestyle changes such as avoiding fatty or spicy foods, eating smaller meals, and not lying down immediately after eating can also help reduce heartburn symptoms alongside medication.

What are the latest findings on alginate-based antacids like Rennie Liquid?

Alginate-based antacids have been studied extensively and are well-established in clinical guidelines for the management of heartburn and mild gastro-oesophageal reflux. Research published in clinical literature supports their use as a first-line option for symptomatic relief, particularly in pregnancy. The NHS and NICE both recognise alginate preparations as appropriate short-term treatments for heartburn and acid reflux. If you're also interested in general digestive wellness, our vitamins and supplements range includes products that may support gut health.

How Should You Use Rennie Liquid Heartburn Relief?

Always shake the bottle well before each use — the suspension can settle between doses, so this step is important for getting the right mix of active ingredients. Use the measuring cup or spoon provided to ensure you take an accurate dose. Do not estimate.

If you find the taste difficult, you can take a small sip of water immediately afterwards, but avoid large amounts of liquid as this may dilute the alginate raft before it forms properly.

What Is the Correct Dose of Rennie Liquid Heartburn Relief?

The dose varies depending on age. Children under 12 should not use this product. Always follow the dosage instructions on the label or as directed by your pharmacist, and never exceed the stated maximum daily dose.

If you regularly need the maximum daily dose to control your symptoms, this is a sign that you should speak to your GP. Frequent or severe heartburn may require a different treatment approach.

When Is the Best Time to Use Rennie Liquid Heartburn Relief?

Rennie Liquid is most effective when taken after meals and at bedtime. This is because the alginate raft needs stomach contents to float on — taking it on a completely empty stomach reduces its effectiveness. Bedtime dosing is particularly useful for people who experience nocturnal reflux or wake with heartburn during the night.

You can also take a dose as soon as symptoms appear at any other time of day. If you know certain foods or activities trigger your heartburn, taking a dose shortly after eating may help prevent symptoms from developing fully.

How Long Can You Use Rennie Liquid Heartburn Relief For?

Rennie Liquid is intended for short-term symptomatic relief only. Do not use it continuously for more than seven days without seeking advice from your pharmacist or GP. If your symptoms persist beyond this period, worsen, or are accompanied by other warning signs — such as difficulty swallowing, unexplained weight loss, persistent vomiting, or dark stools — you must see a doctor promptly.

Long-term, frequent use of antacids without medical supervision is not recommended, as it may mask symptoms of a more serious underlying condition such as gastro-oesophageal reflux disease (GORD) or a peptic ulcer. Your GP can assess whether a longer-term treatment such as a proton pump inhibitor is more appropriate for you.

Do not exceed the recommended dose. If in doubt, speak to your pharmacist.

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Take Rennie at night advised bymy doctor find it very good few places it’s outof stock

What Are the Most Common Side Effects of Rennie Liquid Heartburn Relief?

Most people tolerate Rennie Liquid well, and side effects are generally mild when the product is used as directed. The most frequently reported side effects relate to the antacid ingredients affecting normal digestive function.

  • Constipation — calcium carbonate can slow bowel motility with regular use
  • Flatulence (wind) — a common result of the neutralisation reaction between antacids and stomach acid
  • Chalky or slightly sweet aftertaste

These effects are usually temporary and resolve on their own. Staying well hydrated and maintaining a balanced diet can help minimise constipation if it occurs.

What Are the Less Common Side Effects of Rennie Liquid Heartburn Relief?

Less commonly, some people may experience the following side effects, particularly if the product is used more frequently or at higher doses than recommended.

  • Nausea
  • Stomach discomfort or bloating
  • Rebound acid hypersecretion — where the stomach produces more acid after the antacid wears off, particularly with prolonged use
  • Hypercalcaemia (raised blood calcium levels) with excessive long-term use — symptoms may include muscle weakness, confusion, increased thirst, or frequent urination
  • Raised sodium levels with very high doses — relevant for those on sodium-restricted diets

If you notice any of these less common effects, reduce your dose and speak to your pharmacist. Do not continue using the product at high doses without medical guidance.

What Are the Serious Side Effects of Rennie Liquid Heartburn Relief?

Serious side effects are rare but require immediate medical attention. Stop using Rennie Liquid and seek emergency help if you experience any of the following, which may indicate a severe allergic reaction (anaphylaxis):

  • Swelling of the face, lips, tongue, or throat
  • Difficulty breathing or swallowing
  • Severe skin rash, hives, or itching
  • Sudden drop in blood pressure or feeling faint

Call 999 or go to your nearest A&E immediately if you suspect anaphylaxis. Do not wait to see if symptoms improve on their own.

What Should You Do If You Experience Side Effects of Rennie Liquid Heartburn Relief?

For mild side effects such as constipation or wind, reducing your dose or spacing out your doses may help. If side effects persist or concern you, stop using the product and speak to your pharmacist or GP. You can also report suspected side effects directly to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk — this helps improve medicine safety for everyone.

Never exceed the recommended daily dose, and do not use Rennie Liquid for more than seven days continuously without medical advice. If your heartburn symptoms are not improving, your GP may need to investigate further.

Can Rennie Liquid Heartburn Relief Interact With Other Medicines?

Yes. Rennie Liquid can affect the absorption of several medicines if taken at the same time. The calcium and sodium in the formulation can bind to or alter the absorption of other drugs in the gastrointestinal tract. To avoid interactions, separate your dose of Rennie Liquid from the following medicines by at least two hours:

  • Tetracycline antibiotics (e.g. doxycycline, tetracycline)
  • Iron supplements
  • Antifungal medicines (e.g. itraconazole, ketoconazole)
  • Bisphosphonates (e.g. alendronic acid)
  • Levothyroxine (thyroid medicine)
  • Some HIV antiretroviral medicines

Always inform your pharmacist of all medicines you are currently taking — including prescription, over-the-counter, and herbal products — before starting Rennie Liquid.

If you are concerned about any side effects, contact your pharmacist or GP immediately.

Patient Information Leaflet

Important - Before taking any medication, it is always important to read the Patient Information Leaflet (PIL)

Written and reviewed by our qualified team

GPhC Number: 2233073
Tarun Kumar

Reviewed by:

Tarun Kumar

Superintendent/ Clinical Lead

📖 Find out more about our team of medical content authors and how we ensure the accuracy of our content with our content guidelines.

Content last updated: 31 Mar 2025

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