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Written by: Alex Bussey
Edited by: Mike Martin
Reviewed by the Your.MD medical team
Diarrhoea is when you pass a lot of loose or watery stools. It’s normally the sign of a gastrointestinal infection — where a virus or another germ infects your intestines and irritates the surrounding tissues.
But there are times when diarrhoea can be a sign of a long-term medical condition like Crohn's disease or irritable bowel syndrome (IBS).
Diarrhoea can also be the symptom of a serious bacterial infection that needs to be treated with antibiotics, so it’s important to know when to see a doctor about your symptoms.
Generally speaking, you will need to go to the doctor if:
Diarrhoea can make you lose a lot of water. If this water isn’t replaced, you may start to experience signs of dehydration — such as dizziness or light-headedness, a dry mouth, tiredness or a headache.
Dehydration can also make you feel weak and cause symptoms of fainting or irregular heartbeat (arrhythmia).
To treat it at home, you can try:
If these don’t help a doctor may be able to give you an oral rehydration solution to stop you from getting more dehydrated.
If you’re struggling to keep down water, your doctor may also need to connect you to a drip so that fluids can be delivered straight into your blood.
Diarrhoea normally clears up within a week. If you’ve had symptoms for more than 7 days, there's a chance that it could be more than just a tummy bug.
You might have been infected by a bacteria like shigella, which is often linked to poor hygiene. Shigella causes a condition called bacterial dysentery, which can cause symptoms of diarrhoea for up to 4 weeks.
You could also have a parasitical infection like giardia. This parasite can be found in soil, food, or water that’s been contaminated with animal poo.
These infections are normally treated with a short course of antibiotics, but your doctor will need to test your blood to work out what’s causing your symptoms.
Your doctor may also ask for a stool sample so that they can work out what type of germ is causing your diarrhoea.
Diarrhoea that lasts for more than 4 weeks is called chronic (or long-term) diarrhoea.
It’s often the result of a food intolerance, which is where your body has trouble digesting something like milk, fruit sugars (fructose) or artificial sweeteners like sorbitol or xylol.
But chronic diarrhoea can also be a sign of an underlying health condition.
This is where part of your bowel becomes inflamed and you experience symptoms of diarrhoea, stomach cramps, weight loss and fatigue.
The causes of Crohn’s disease aren’t clear, but doctors think it could be linked to your genes, a problem with your immune system or problems with the bacteria that live in your intestines.
IBS often causes episodes of bloating, diarrhoea and constipation that come and go for several weeks or months at a time.
The causes of IBS are also unknown and there's no cure at the moment, but the condition can be managed with medication and changes to your diet.
This is a rare condition that causes your body to have an immune reaction to gluten in your diet. This causes damage to your small intestine, triggering symptoms of abdominal pain, bloating and diarrhoea.
These problems need to be treated by a specialist, so it’s important to see a doctor if you’ve had diarrhoea for more than a few weeks.
A doctor will probably order tests to help diagnose any underlying problems, including blood tests, stool samples or a fasting test — where you will be asked to avoid certain foods to see if they could be causing your symptoms.
Your doctor may also order an endoscopy. This is where a small camera (called an endoscope) is inserted inside your digestive tract to check for any damage that could be linked to a condition like Crohn's disease or coeliac disease.
You should always see a doctor if you have diarrhoea and you notice blood in your stool.
Blood in your stool can be a sign of:
But blood in your stool can also be a sign of bowel cancer.
This type of cancer is most common in people over 60, but you can get it at any age and it can be very serious. Bowel cancer is also easier to treat if it's caught early, so if you notice blood in your stool, it’s best to get it checked straight away.
Other symptoms of bowel cancer include abdominal (or tummy) pain, bloating or discomfort when you eat, losing your appetite or losing weight unexpectedly.
If your doctor thinks that you might have bowel cancer, they will probably order a colonoscopy. This is a common surgical procedure where a small camera is inserted into the anus, and used to look for any signs of cancer.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.