How are IBS and CIC diagnosed?

What to expect when seeking treatment for persistent constipation symptoms and why diagnosis can be challenging.

An exam room at a doctor's office. Diagnosing chronic constipation usually begins with a physical exam.

Written by Jameson Kowalczyk. Medically reviewed in January 2024 by Ann Wendling, MD, MPH.

Although irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are common, the two conditions can be challenging to diagnose and difficult to differentiate from one another. Both cause persistent, long-term constipation and share a number of other overlapping symptoms. While some criteria consider IBS-C and CIC separate disorders, others argue that they are part of the same continuum of disorders.

Here, we look at how IBS-C and CIC are diagnosed.

Diagnosis of exclusion

One challenge of diagnosing IBS-C or CIC is the fact that the symptoms are non-specific. In medical terms, non-specific refers to symptoms that can have a number of different causes and do not point to a clear and obvious diagnosis. Symptoms associated with IBS-C and CIC include:

Constipation (having fewer than 3 bowel movements per week)
Abdominal pain
Gas and bloating
Feeling that a bowel movement is incomplete
Straining during bowel movements
Passing stools that are hard, dry, or lumpy
Changes in bowel habits

Another challenge of diagnosing IBS-C and CIC—the causes of these conditions are unclear and there is no test for either disease. The diagnostic process involves eliminating the other possibilities that could be causing these symptoms. This is called a diagnosis of exclusion. When all other possibilities have been excluded, IBS-C or CIC is left as the only remaining explanation. Whether a person has IBS-C or CIC depends on their specific symptoms and the severity of those symptoms (which are discussed below).

Exams and tests to diagnose IBS-C and CIC

When looking for the cause of constipation, a healthcare provider will complete a physical exam and review your medical history, including symptoms, family history, recent infections or illnesses, medications, and mental health. A blood panel will typically be a part of the physical exam. Other lab tests may be ordered to check for lactose intolerance, bacterial overgrowth in the small intestine, and abnormalities in stool samples. In some cases, a healthcare provider may order other exams that look at the physical structure of the GI tract. These can include imaging tests like X-rays or CT scans, and procedures like endoscopy, colonoscopy, or sigmoidoscopy.

Diagnosing IBS and CIC

The diagnostic criteria for IBS and CIC are continuously being updated, as healthcare providers and researchers learn more about the disorders, how and why symptoms manifest, and the experiences of patients afflicted by long-term constipation. In the past, IBS-C and CIC were considered separate disorders. More recently, some have argued that the conditions a part of the same continuum of functional GI disorders. While symptoms overlap, traditionally the difference between the two is that abdominal pain was a primary symptom of IBS and a secondary symptom of CIC.

There can be much overlap among the symptoms of CIC and IBS-C, symptoms can change over time, and GI disorders are a different experience for every person. The most important thing to do if you have persistent constipation and related symptoms is to work with a healthcare provider who can accurately diagnose the cause and come up with an appropriate treatment plan.

Article sources open article sources

Hung-Da Chena, Ming-Jong Bair, et al. Similarities and differences between IBS-C and FC with regards to symptomatology, sleep quality and psychological attributes. Journal of the Formosan Medical Association, January 2020. Vol. 119, No. 1.
Brooks D. Cash. Understanding and Managing IBS and CIC in the Primary Care Setting. Gastroenterology & Hepatology, 2018. Vol. 14, No. 5.
UpToDate. Clinical manifestations and diagnosis of irritable bowel syndrome in adults.
Kewin T. H. Siah, Reuben K. Wong, and William E. Whitehead. Chronic Constipation and Constipation-Predominant IBS: Separate and Distinct Disorders or a Spectrum of Disease?
Eamonn M. M. Quigley. Editorial: differentiating chronic idiopathic constipation from constipation‐predominant irritable bowel syndrome – possible and important? Alimentary Pharmacology and Therapeutics, 2015. Vol. 41, No. 12.
Eric D. Shah, Christopher V. Almario, Brennan M. R. Spiege, and William D. Chey. Lower and Upper Gastrointestinal Symptoms Differ Between Individuals With Irritable Bowel Syndrome With Constipation or Chronic Idiopathic Constipation. Journal of Neurogastroenterology and Motility, 2018. Vol. 24, No. 2.
UpToDate. Patient education: Irritable bowel syndrome (Beyond the Basics).
Cleveland Clinic. Irritable Bowel Syndrome (IBS).
Mayo Clinic. Irritable Bowel Syndrome.
Leslie J. Donato. A Game of Exclusion: Laboratory Testing for Irritable Bowel Syndrome. The American Association for Clinical Chemistry (AACC), May 2017.
National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of Irritable Bowel Syndrome: How do doctors diagnose IBS?
Max J Schmulson and Douglas A Drossman. What Is New in Rome IV. Journal of Neurogastroenterology and Motility, 2017. Vol. 23, No. 2.