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How long does it take for Imodium to work?

Also called loperamide, Imodium is the common name for a go-to treatment for diarrhoea, in particular sudden diarrhoea. When the time comes for Imodium, you’ll probably need it to work as quickly as possible. So if you’re wondering how long it takes to feel the benefits, then read on.

Diarrhoea is a very common condition and not usually a cause for concern here in the UK. The most common cause is gastroenteritis. People often suffer diarrhoea when travelling abroad when they are exposed to food they are not used to eating. It can also be the result of stress, allergies, medication or Irritable Bowel Syndrome (IBS).

What causes diarrhoea?

Diarrhoea occurs when the cells in your small intestine or colon become irritated, which increases the movements in your intestines. This causes fluids and salts to be passed through the colon far too quickly to be absorbed. As more fluid stays in your intestine as the food travels through, it results in watery, more frequent bowel movements.

Imodium slows down the movement of digested food through the colon. This helps your body absorb more of the water through your intestines, making your stool firmer and ensuring you don’t have to go to the toilet as often.

How long does Imodium take to work?

The medicine aims to improve your symptoms in under an hour. Bear in mind however that Imodium will be most effective roughly 16 - 24 hours after you first take it.

Depending on the cause of your diarrhoea, it may take 2 to 4 days for your diarrhoea to subside. In most cases, Imodium can bring relief from diarrhoea within 48 hours.

What to look out for when buying Imodium?

Imodium comes in various forms, including:

  • Tablets and hard or soft capsules. You can usually take these with a drink of water as you would any other medicine in pill form.
  • Tablets that melt on your tongue. Often called ‘Imodium Instants’ or ‘Imodium Instant Melts’, you should put it on your tongue and allow it to slowly dissolve. It is then acceptable to swallow the rest with a drink.
  • Imodium Syrup (labelled 1mg/5ml). This is only available on prescription. Take four spoonfuls (5ml each) or one 20ml dose from a measuring cup. Be sure to use the measuring cup or spoon to help you measure the right dose. Ask your pharmacy if you are not provided one.

If you are unsure as to which form is right for you, talk to a pharmacist about your symptoms, and they should be able to help you make the right decision.

Some supermarkets and pharmacies sell in-house brands of loperamide capsules, commonly referred to as "anti-diarrhoeal" or "diarrhoea relief" on the label.


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  • Relieves diarrhoea
  • Different forms available
  • Dispatched from a UK registered pharmacy

Some products even contain the term "IBS" to tell that customers that they can be used for diarrhoea resulting from irritable bowl syndrome. However, products without IBS in their name can also be used by people with IBS.

According to the NHS, here are some things to think about when taking Imodium:

  1. Start with a small dose. This makes it less likely that the medicine works too well and gives you the opposite issue - constipation.
  2. The usual dose is 1-2 mg, but you can take more if needed. Try not to go over 8 mg unless your doctor agrees that it's a good idea.
  3. If your Imodium is in tablet form, take 2 tablets immediately. Then you can take one more for each bout of diarrhoea you get thereafter.
  4. Diarrhoea can dehydrate you quickly, so remember to drink plenty of water to keep your body hydrated.

Remember: Imodium is a short term solution

Try not to make a habit of taking Imodium as it won't address the root cause of your sudden bowel disturbances. Once you have gained control of your bowel movements, look for the reason why you have diarrhoea in the first place, and tackle it head-on.

Do not take Imodium for more than 48 hours without speaking to a doctor, if you initially bought it to treat short-term diarrhoea. Most cases of diarrhoea will improve within a week. Talk to your doctor if your symptoms of diarrhoea haven't improved in 7 days. After this time, it's important to begin to treat the effects of diarrhoea, such as dehydration.

Try not to take more than the recommended dose. Although it is unlikely that you will be affected by taking an additional dose of Imodium, greater doses can cause severe heart problems and can even lead to a rapid or uneven heartbeat (tachycardia). If you're concerned that you may have taken too much, talk to your pharmacist or doctor.

Authored & Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist
Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Published on: 14/08/2019 Reviewed on: 18/05/2023
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