Losec Gastro Resistant Capsules

What is Losec?

Losec is a prescription-only medicine containing the active ingredient omeprazole, which belongs to a group of medicines known as proton pump inhibitors (PPIs). PPIs help control the level of acid in your stomach, meaning they can relieve symptoms of acid reflux, heartburn and indigestion.

Losec is available as gastro-resistant capsules designed to be released in the intestine rather than the stomach. Because of this, they have a coating that protects the active ingredient from stomach acid.

What are Losec capsules used for?

While Losec capsules can be used to treat other conditions, like stomach ulcers, taking them for these reasons requires closer monitoring.

Due to this, Chemist4U will only prescribe Losec gastro-resistant capsules for:

• short-term treatment of acid reflux and indigestion that has not responded to over-the-counter antacids
• gastroprotection for people on courses of stronger non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen.

How do Losec capsules work?

Losec capsules contain the active ingredient omeprazole and look to reduce stomach acid by blocking the pumps in the stomach lining that produce acid.

The capsules are gastro‑resistant, which means they pass through the stomach intact and release the medicine in the intestine, where it can be absorbed properly.

How long does Losec take to work?

While Losec starts reducing stomach acid within a few hours of taking it, you might not notice symptom relief immediately.

Many people report an improvement in heartburn or acid reflux within the first two days. Since the effects of the treatment gradually build up, it’s most effective at three or four days when it has reached maximum acid-reduction in the stomach.

How to take Losec capsules

You should always take Losec capsules as you have been advised by your doctor or pharmacist. If you are unsure then you should ask them first.

Losec capsules can be taken with or without food, and should be:

• taken at the same time every day
• taken with a whole glass of water
• not crushed, chewed or opened

Losec dosage

The recommended dose for Losec capsules change depending on the reason you are taking it.

For treating symptoms of gastro-oesophageal reflux disease (GORD), like acid reflux and heartburn, you should take:

• 20mg once a day for 4-8 weeks (if your oesophagus has been slightly damaged)
• 10mg once a day (if your oesophagus has not been damaged)
• 10mg – 20mg once a day depending on the advice from your pharmacist

If taking Losec to help prevent damage that could be caused by NSAIDs, the recommended dose is:

• 20mg once a day

If your symptoms last longer than 4 weeks, we recommend that you discuss this with your own doctor.

What if I miss a dose?

If you forget to take a dose of omeprazole, take it as soon as you remember.

However, if it’s nearly time for your next dose, skip the missed one and carry on as normal. Do not take a double dose to make up for a forgotten dose.

Best time to take Losec

When using Losec it’s important to try and take it as the same time every day, preferably in the morning.

This is because the active ingredient, omeprazole, works by switching off the pumps that produce acid in your stomach. These pumps are most active in the morning, before food is eaten, meaning taking Losec earlier helps control your acid levels more effectively.

Losec side effects

As with any medicine, taking Losec may cause side effects. Importantly, they are usually mild and go as your body gets used to the medication.

Common side effects of taking Losec include:

• headaches
• stomach pain
• nausea or vomiting
• constipation or diarrhoea
• farting more than usual

This is not a complete list of side effects, for a full list, read the patient information leaflet.

When to seek medical help

If you have any side effects that bother you or do not go away, you should speak to a doctor or pharmacist as they may be able to give you advice on how to reduce your symptoms.

If you are experiencing the rarer, more serious side effects of omeprazole you should contact your doctor or call 111. They can include:

• having very low levels of vitamin B12 (symptoms can look like tiredness, dizziness, weakness or twitching of muscles)
• weakening of bones (warning signs can look at breaks/fractures from small bumps, severe back pain, and weak grip strength)

If you think you may be having a severe allergic reaction, you should call 999 immediately. Try and get to a hospital as soon as you can but do not drive yourself there. If no one can take you, wait till an ambulance can collect you.

When not to use Losec

Losec is suitable for most adults, but it may not be right for everyone. In some cases, it should not be used at all, and in others you may need to speak to a doctor or pharmacist before starting treatment to make sure it’s suitable for you.

Do not take Losec if:

• you have ever had an allergic reaction or serious side effect from omeprazole or another proton pump inhibitor (PPI)
• you have osteoporosis (weakened bones)
• you have a kidney or liver condition

Speak to a doctor or pharmacist before taking Losec if:

• you are due to have medical tests, including blood tests, tests for certain tumours, or a gastroscopy, as Losec can affect the results
• you are pregnant or breastfeeding and want to check that Losec is suitable for you

Frequently asked questions about Losec capsules

Is Losec the same as omeprazole?

Yes, Losec is a brand name for omeprazole, which is the active ingredient that reduces stomach acid.

Can you buy Losec over the counter?

No. While low‑strength omeprazole products are available without a prescription for short‑term heartburn, higher strengths like Losec require a prescription.

Can Losec cause constipation?

Constipation is a possible side effect of Losec, although it’s not very common. If it does occur, it’s usually mild and may settle as your body adjusts to the medicine.

Drinking plenty of fluids, eating fibre‑rich foods, and staying active can help. If constipation becomes troublesome or does not improve, speak to a pharmacist or doctor for advice.

Can you take Losec and Gaviscon together?

Yes, they can be taken together, as they work in different ways to relieve symptoms. However, it’s usually recommended that omeprazole is taken on an empty stomach, at the same time each day, and that Gaviscon is taken just after meals.

Can I take Losec after eating?

Yes, Losec can be taken with or without food, however, for the best results it’s recommended to take it before a meal.

Sources

• Omeprazole. (NHS). [Accessed 27 April 2026]