Most of the time, stomach acid quietly gets on with its job without you really noticing. But if some of it escapes up towards your throat – a common occurrence known as acid reflux – it can trigger familiar symptoms like heartburn (a burning feeling in the chest) or an unpleasant sour taste in your mouth.

In this guide, we’ll look at what stomach acid does, why it sometimes causes discomfort and the simple steps you can take to feel more comfortable. We’ll also cover when over-the-counter options like Rennie® may help, and when it might be a good idea to check in with a healthcare professional.

The role of stomach acid

Your stomach is designed to be a very acidic environment – far more acidic than most other parts of the body.

This acidic mix has several important jobs:

• Digesting food – stomach acid helps break down the structure of proteins and switches on enzymes that break food into smaller pieces your body can absorb
• Helping you absorb nutrients – certain vitamins and minerals, including vitamin B12, iron and some forms of calcium, rely on stomach acid to help release or convert them into forms that can be absorbed in the gut
• Defending against germs – many bacteria and other microbes can’t survive in such a low-pH environment, so stomach acid acts as part of your immune defence against unwanted bugs in food and drink

Your body usually keeps stomach acid tightly controlled. Specialised cells in the stomach wall ramp up acid production when you eat, then ease off again between meals. A ring of muscle at the top of the stomach (called the lower oesophageal sphincter) also works like a natural valve, helping to keep that acid safely where it belongs.

When this delicate balance is disturbed, stomach acid can shift from being a helpful digestive partner to a source of discomfort.

What causes stomach acid-related discomfort?

Many everyday factors can make stomach acid-related symptoms more likely. Common triggers of heartburn and acid reflux include:

• Certain foods and drinks – such as coffee, tomatoes, chocolate, fatty foods or spicy dishes
• Alcohol – which can irritate the stomach lining and relax the muscle that normally prevents acid reflux
• Smoking – this can weaken the lower oesophageal sphincter, making it easier for acid to flow back into the oesophagus
• Stress and anxiety – these can affect how your digestive system works and may increase muscle tension, making symptoms feel worse
• Hormonal changes – increases in hormones such as progesterone and oestrogen can affect digestion
• Pregnancy – growing pressure on the stomach and hormonal shifts can both contribute to reflux
• Being overweight – extra pressure on the stomach can make reflux more likely

Underlying medical conditions, such as a hernia or stomach ulcers, and some medicines (like certain anti‑inflammatories) can also trigger or worsen discomfort.

If you’re unsure what’s causing your symptoms, it’s always worth checking in with a healthcare professional.

How stomach acid can lead to acid reflux and heartburn

Heartburn is a burning sensation in the chest, often after eating, caused by stomach acid travelling up into the oesophagus – a process known as acid reflux.

Normally, the lower oesophageal sphincter acts like a valve between your oesophagus and your stomach. If this muscle weakens, some of that acidic stomach content can move the wrong way, irritating the sensitive lining of your food pipe. When this happens, you might notice a burning feeling in the middle of your chest, or an acidic or sour taste in your mouth.

These symptoms may feel worse when you bend over, lie down or after eating a large meal.

Why stomach acid symptoms can feel worse during pregnancy

Indigestion, heartburn and acid reflux are very common in pregnancy.

You’re more likely to notice these symptoms during pregnancy because of:

• Hormonal changes that naturally occur during pregnancy
• Relaxation of the muscles between your stomach and gullet, which may make reflux more likely
• The growing baby pressing on your stomach, especially later on in pregnancy
• Slower digestion, as the food moves more gradually through your system
• Weight gain as your pregnancy progresses

The good news is that for most people, these symptoms are temporary and usually settle once the baby is born. In the meantime, small lifestyle tweaks – like eating little and often and sitting upright while you eat – can help ease discomfort.

If you’re pregnant, it’s important to speak to a pharmacist or doctor before taking any medicine, including over‑the‑counter products like antacids. They can advise which options are suitable for you and when.

Tips for managing symptoms day to day

Small, everyday changes can make a real difference to how your stomach feels. If you’re dealing with occasional heartburn, indigestion or reflux, you might find it helps to:

• Adjust portion sizes – try smaller, more frequent meals instead of very large ones
• Notice your triggers – keep a simple food and symptom diary to spot patterns. Common culprits may include rich, spicy or fatty foods, chocolate, citrus fruits, caffeine, fizzy drinks and alcohol
• Avoid lying down straight after eating – aim to finish eating at least three hours before lying down or going to bed
• Raise the head of your bed – if night‑time heartburn is a problem, elevating the head of your bed by 10–20cm (using wood or books) can help reduce reflux. Avoid using extra pillows, as this can put pressure on your stomach and worsen symptoms

Looking after your lifestyle can also play a role in easing discomfort. Staying active, keeping to a healthy weight, managing stress and stopping smoking can all support smoother digestion and help keep symptoms at bay.

When over-the-counter treatment may help

If you find yourself getting heartburn or acid reflux regularly, it’s a good idea to speak to a pharmacist or doctor for advice.

For mild, occasional symptoms, a pharmacist may recommend over‑the‑counter medicines such as antacids or alginates.

Rennie® Peppermint, for example, is an antacid that works by neutralising excess stomach acid, helping to relieve symptoms of heartburn, indigestion and acid reflux. Available in tablet form, Rennie® Peppermint is convenient to carry around and can be taken discreetly when symptoms appear, following the instructions on the pack.

Your pharmacist can help you decide which product is right for you, explain how to use it safely and let you know when it might be time to speak with your GP for further advice.

When should you speak to a doctor?

Most heartburn and reflux can be managed at home, but there are times when it’s best to speak to a doctor. See a GP if:

• Lifestyle changes and pharmacy medicines aren’t helping symptoms
• You have heartburn most days
• You also have other symptoms, like food getting stuck in your throat, frequent vomiting or unexplained weight loss

A GP can provide alternative treatments and help rule out any more serious causes of your symptoms.

Stomach acid plays an important role in digesting food, helping your body digest and absorb nutrients and defending against harmful bacteria. But when it ends up where it shouldn’t – it can lead to uncomfortable symptoms like heartburn, indigestion and acid reflux.

The reassuring news is that these symptoms are very common and, in many cases, can be managed with a combination of everyday lifestyle changes and short‑term over‑the‑counter treatments, such as antacids.

By listening to your body, noticing your personal triggers and seeking professional advice when you need it, you can keep stomach acid symptoms under control – so you can focus on what matters most, like enjoying time with friends and family, without discomfort getting in the way.