How Is Irritable Bowel Syndrome (IBS) Diagnosed?

Diagnosing IBS can be tricky since there isn’t a single test or feature that can identify whether or not someone has IBS. Reaching a diagnosis will require a lot of investigation to rule out other conditions with similar symptoms. If you suspect that you might have IBS, this diagnosis will help you to understand the process ahead.

How is IBS diagnosed?

Irritable bowel syndrome (IBS) is a condition that affects the gastrointestinal system and causes symptoms like abdominal pain, constipation, diarrhea, bloating, and gas. We don’t know exactly why IBS occurs, but we do know that certain triggers can contribute to IBS symptoms and severity:

• Life stressors

• Infection

• Muscle contractions that are too strong or too weak 

• Diverticulitis 

• Disruption to gut flora

• Disrupted brain signals¹

IBS often goes undiagnosed; only around 30% of people in the U.S. will reach out to a doctor about their IBS symptoms². When people are diagnosed, they’re much more likely to be women and under 50 years of age. An estimated 60–65% of people who report IBS are women, and people over 50 are 25% less likely to be diagnosed with IBS² ³.

So how is IBS diagnosed?

Reaching a diagnosis first requires your doctor to take a detailed medical history and note the full range of your current symptoms. Then a range of tests will be undertaken to determine:

1. If your symptoms are consistent with IBS

2. If your symptoms might be due to another condition

What tests are done for IBS?

Unfortunately, there is no specific test to determine whether someone has IBS, so the testing revolves around seeing if IBS is a good fit and then eliminating conditions with similar symptoms.

Diagnostic criteria for IBS

The Rome IV Diagnostic Criteria are often used as an aid to determining whether a patient’s symptoms might fall under IBS⁴. The criteria state that patients must have recurring abdominal pain for the previous three months lasting on average at least one day a week, and at least two of the following to be diagnosed with IBS:

• Pain during bowel movements 

• Pain linked to a change in frequency of stool

• Pain linked to a change in the appearance of stool⁵

The Rome IV criteria are used as a tool to help a physician decide whether IBS might be an option. However, just because someone meets the criteria doesn’t mean that they definitely have IBS. Because of this, most doctors will use them along with further diagnostic modalities.

Test to rule out other conditions

Other tests that you may encounter while in the process of being diagnosed include:

Blood tests

You might be required to have blood tests to rule out disorders like celiac or inflammatory bowel disease, which can have very similar symptoms to IBS.

Colonoscopy

Colonoscopies are used to examine the colon and determine if an inflammatory condition or cancerous growth might be responsible for the IBS-like symptoms.

Parasite tests

Parasites like giardia can lead to stomach cramps, bloating, and diarrhea—similar symptoms to IBS.

CT scan/X-ray

CT scans and X-rays can be used to rule out other conditions that might be causing abdominal pain.

Stool tests and examinations

Fecal tests are commonly undertaken when figuring out if a patient has IBS. These tests can help rule out other conditions that can mimic the symptoms of IBS. 

Food allergy tests

Sensitivity or allergies to foods or food intolerances, such as lactose or gluten intolerance, should be evaluated because they can cause symptoms similar to IBS. 

Breath tests

Breath tests can be used to determine if you have other issues that might be causing your symptoms, like bacterial overgrowth in the small intestine or lactose intolerance. 

Upper endoscopy

An upper endoscopy involves placing a tube with a camera on the end down the throat and into the stomach and small intestine, where samples can be taken to test for conditions like acid reflux, bacterial overgrowth, or celiac disease¹.

Can you self-diagnose IBS?

Diagnosing IBS can be a somewhat frustrating process to go through, but you cannot diagnose it yourself. Many other medical conditions could be responsible for the symptoms that you are attributing to IBS. Because of this, it’s important that you consult your doctor about your concerns and undergo the necessary tests to determine if you do have IBS or another problem.

While you can’t self-diagnose IBS, keeping a diary of your symptoms and food intake is something only you can do. These can be especially useful in helping your doctor reach the correct diagnosis. There are also apps that you can use to make recording your symptoms even easier, such as:⁶

• Monash University FODMAP diet

• mySymptoms Food Diary (Lite)

• My Healthy Gut

• FODMAP Helper - Diet Companion 

• GI Bodyguard

After the diagnosis is made, your symptom diary can continue to play an important role in tracking whether or not your IBS treatment is working for you. Things to note in your symptom diary include:

• The symptoms you have been experiencing like bloating, constipation, diarrhea, fatigue 

• When the symptoms occur and for how long, e.g., three episodes of diarrhea on Monday from 2 pm to 4 pm 

• The severity of your symptoms, e.g., severe abdominal pain last Friday, mild abdominal pain today 

• The types of food you eat and when you eat them, which can help tie IBS symptoms to specific food triggers 

• The frequency and type of your bowel movements

• Any IBS triggers that you notice, like stress, drinking coffee or alcohol, sleep problems

Do you need to have a colonoscopy to diagnose IBS?

A colonoscopy won’t be used directly to diagnose you with IBS, but it can help your doctor figure out if something else is going on. IBS has many differential diagnoses, meaning that there is a range of other conditions that can also fit the symptoms of IBS. Because of this, tests like endoscopy are used to rule out those other conditions.

You might undergo a colonoscopy to determine if your IBS-like symptoms are actually the result of:⁷

• Crohn’s disease

• Ulcerative colitis 

• Bowel cancer/colorectal cancer 

• Celiac disease

What happens after you get diagnosed with IBS?

Types of IBS

After you are diagnosed with IBS, your doctor will designate what type you have. There are three main categories:⁸

1. Constipation-predominant (IBS-C)

IBS-C is one of the most common types of IBS. Patients experience hard stools and often suffer from painful bowel movements, gas, bloating, and abdominal pain. They generally have infrequent bowel movements that are difficult to pass.

2. Diarrhea-predominant (IBS-D)

Patients with IBS-D, on the other hand, tend to have no trouble passing stools and frequently have to go to the bathroom. Their bowel movements are mostly loose or watery, so they tend to experience abdominal cramping and pain, gas and bloating, and a frequent urge to go to the bathroom, often many times a day.

3. Mixed (IBS-M, sometimes called IBS-A for alternating)

IBS-M, or IBS-A as it is sometimes called, is a type of IBS that combines both IBS-C and IBS-D symptoms. These patients experience both constipation and diarrhea, which are generally alternating, as well as gas and abdominal pain.

IBS treatment

The next step after being diagnosed with IBS is to establish a treatment plan. The appropriate treatment for IBS will depend on which type the patient has and the specific symptoms they are experiencing.

IBS treatments are focused on reducing the severity and duration of symptoms. Treatment options can include: 

Medication

• Anti-diarrhea medication: Diarrhea is a common symptom of IBS, and when needed, antidiarrheals might be prescribed to help slow down the gastrointestinal system. 

• Laxatives: Constipation can also be a concern for IBS patients, so laxatives might be given to help loosen stools.

• Antibiotics: Some patients with IBS diarrhea can experience an overgrowth of intestinal bacteria and may be prescribed antibiotics.

• Antidepressants: There is a strong link between depression and IBS, so antidepressants might be prescribed to improve mental health and to help reduce pain and constipation.

• Pain medication: Patients often experience painful episodes, so pain medication tends to be a regular component of IBS treatment. 

• Anticholinergic medications: Painful intestinal spasms often occur in IBS, so these medications can be given to calm the intestinal muscle movements and stop the spasms⁵.

Lifestyle changes

Certain lifestyle changes might also be recommended to help ease the symptoms of IBS. Stress can have a significant impact on gut health⁹, so activities or techniques that help reduce and better manage stress can be very helpful for people with IBS.

These may include:

• Meditation 

• Therapy¹⁰

• Smoking cessation

• Healthy sleep habits

• Regular exercise 

• Removing stressful triggers¹

Diet

Dietary choices can greatly affect IBS symptoms, so after diagnosis, your treatment plan might include eliminating food and drink that trigger IBS. Potential IBS triggers include:¹¹

• High FODMAP vegetables: mushrooms, garlic, onion, asparagus, cauliflower, green peas

• High FODMAP fruits: apples, peaches, dried fruit, watermelon, mango

• Dairy: cow’s milk 

• Gluten: wheat, rye, barley 

• Legumes and beans 

• Alcohol 

• Caffeine

When to see a doctor

IBS can be manageable with medication and lifestyle and dietary changes, but you should reach out to your doctor or specialist if you experience new symptoms or your symptoms become more severe.

Specific symptoms that you should take note of and inform your doctor about include:¹²

• Blood or mucus in your stool 

• Severe pain or cramping 

• Severe constipation or diarrhea 

• Weight loss

• Fevers

• Symptoms that wake you up at night

However, if you haven’t yet been diagnosed but think you have IBS, then it pays to tell your doctor about all your symptoms as soon as possible. This will help you to get the right diagnosis and treatment quickly. 

The lowdown

Diagnosing IBS is about establishing whether the symptoms fit and eliminating similar conditions with diagnostic tests. Making the diagnosis is an important step to helping patients get the medical care and advice needed to improve their symptoms and quality of life.

If you think you might have IBS, make a note of your symptoms and reach out to your doctor for an evaluation. That way, you can receive a diagnosis and the appropriate treatment for your condition so you can get to feeling better.