The Key Blood Tests for IBS Diagnosis (And How to Monitor It)

Did you know that every year in the United States, 2.4 million people visit their doctors for IBS treatment? 

To receive an IBS diagnosis, your medical professional will review the symptoms you’ve listed, as well as your family history, and complete a physical exam. In order to accurately diagnosis you with this disease, doctors will also often order a blood test to rule out other potential health problems. 

If you’ve had pain related to your bowel movements, pain in your abdomen or you’ve noticed changes in your bowel movements, talking to your doctor about your symptoms is important to get your health back on track. If you’re looking to learn more about the blood tests that your doctor ordered for you or if you’re looking to take your health into your own hands and order blood tests for yourself, we’ve come up with a complete guide to give you a better understanding of an IBS diagnosis. Keep reading to learn more! 


In the majority of individuals who experience IBS, there are times that the symptoms of this disease worsen, while there are other times where the symptoms improve or even completely disappear. The symptoms and signs of IBS vary from person to person, but the most commonly reported symptoms are: 

• Abdominal pain, cramping or bloating that is typically relieved or partially relieved by passing a bowel movement
• Excess gas
• Diarrhea or constipation, sometimes alternating bouts of diarrhea and constipation
• Mucus in the stool
• Weight loss
• Diarrhea at night
• Rectal bleeding
• Iron deficiency anemia
• Unexplained vomiting
• Difficulty swallowing
• Persistent pain that isn’t relieved by passing gas or a bowel movement 

Risk Factors 

Doctors aren’t exactly sure what causes irritable bowel syndrome. However, there are several risk factors that seem to contribute to the likelihood of an individual receiving an IBS diagnosis. These factors include: 

  • Age – While IBS can affect all age groups, it’s more likely to affect people in their teens, all the way through their 40s. 
  • Gender – Women are twice as likely to develop IBS than men are. While it’s not clear why women are more likely to develop this, many doctors believe that hormone fluctuations can cause the development of IBS.
  • Stress levels – Individuals with IBS often are seen to have trouble managing their stress levels. 
  • Family history – This disease seems to be passed down through families, while no research is available to support this theory. 

Key Lab Tests Diagnosis of IBS

Are you looking to learn more about the key lab tests that are used for IBS diagnosis? Here’s everything you need to know: 

1. C-Reactive Protein (CRP)

CRP, also known as the C-Reactive Protein test, is a blood test that measures the amount of inflammation that’s found in the body. This protein is created in the liver, and higher quantities of CRP are produced when the body is responding to inflammation.

In a healthy body, there aren’t any C-Reactive Protein markers measured in the blood. However, in people with IBS or Celiac Disease, there CRP can be detected in the blood.

2. ESR

ESR stands for Erythrocyte Sedimentation Rate, which is a type of blood test that measures how quickly your red blood cells (erythrocytes) fall to the bottom of a test tube that contains your blood sample. In healthy patients, the erythrocytes slowly settle to the bottom of a test tube. 

When red blood cells fall to the bottom of a test tube quickly, it’s an indicator that there’s inflammation in your body. An ESR test can help doctors determine if you have a condition that causes inflammation, such as IBS. ESR tests are not only used to diagnose someone with IBS but can also help medical professionals monitor your health condition during treatment.

3. CBC

If your doctor suspects that you have IBS, a complete blood count (CBC) test must be completed. A CBC can help confirm this autoimmune condition if the main symptom that you’re experiencing is diarrhea, which is an indication that you may have IBS-D. 

A complete blood count measures the number of red blood cells, the number of white blood cells, the total amount of hemoglobin available in your blood, the percentage of red blood cells in your blood, and platelet count. Having a CBC test completed can help your doctor to rule out other possible conditions, such as an infection, causing the symptoms that you’re experiencing. 

4. Comprehensive Metabolic Panel

In some people who have IBS, a symptom that they’ll report is weight loss. A comprehensive metabolic panel will allow medical professionals to evaluate your health to see if you have an underlying metabolic disorder. In addition, a comprehensive metabolic panel will provide the medical professionals with insight on if you’re experiencing any electrolyte imbalances or dehydration if you’re experiencing diarrhea. 

5. Vitamin D 25-Hydroxyvitamin D (D2, D3)

Recent studies have suggested that individuals with IBS are also experiencing  Vitamin D deficiency. While research hasn’t yet made it clear why people with IBS experience a Vitamin D deficiency, ensuring that your body has a healthy level of Vitamin D promotes a healthy immune system, bone health, and supports gut health.  

6. Vitamin B12

Several of the symptoms of IBS and a Vitamin B12 deficiency are very similar, which is why it’s important to have your B12 levels checked before you receive a diagnosis. A Vitamin B12 blood test can tell medical professionals if they symptoms you’re experiencing are a result of a vitamin deficiency. If your Vitamin B12 levels are a healthy range, it can help your doctor to rule out symptom-related vitamin deficiency.  

7. Iron, Total and Total Iron Binding Capacity

Did you know that iron deficiency anemia is considered to be a gastroenterological disorder? That’s because some of the leading causes of iron deficiency are due to menstruation blood and blood loss caused by gastrointestinal disease.

Blood loss in the intestine and/or the stomach can’t be matched by iron absorption, which would cause an iron deficiency. By taking a look at your test results for your total iron and your iron-binding capacity (your body’s ability to bind the protein to iron found in your blood) will provide medical professionals with insight if your IBD is causing anemia. As a result, this can help your doctor diagnose you with IBS, or point them in the direction of another diagnosis, such as for Crohn’s disease. 

8. Ferritin

Iron in your body is stored in your body with the help of protein that’s called ferritin test. By measuring the level of ferritin found in your body, doctors will be able to identify if you have inadequate levels of this vital protein. Low ferritin levels will show up on a blood test long before an iron deficiency would show on a complete blood count, which is why this blood test plays a vital part in diagnosing IBS or another type of gastrointestinal disease. 

9. Fecal Occult Blood

fecal occult blood test checks stool samples for hidden blood that isn’t identifiable by the naked eye. If there’s occult blood found in the stool, it’s a warning sign that there are polyps in the rectum of the colon. In addition, occult blood found in the stool can be an indicating sign of colon cancer.

Since occult blood is only found in small amounts, a chemical process is used to identify if there’s any occult blood in a fecal sample. Receiving this test will help your doctor to identify other possible hidden health conditions that you may be experiencing, resulting in narrowed down diagnosis. 

10. Anti-tissue Transglutaminase (anti-tTG) antibodies, IgA

Anti-tTg is a test that’s used to diagnose celiac disease. Tissue transglutaminase is an enzyme that’s responsible for fixing the damage in your body. In individuals with celiac disease, their bodies make antibodies to attack the enzyme. Testing positive for this antibody is a step towards receiving the proper diagnosis for the symptoms you’re experiencing. 

11. Quantitative Immunoglobulin A (IgA)

This blood test measures the level of the immunoglobin antibodies in the blood, which are responsible for fighting off infection. If there’s a high level of Quantitative Immunoglobulin A found in your test results, it’s a sign that your body is experiencing inflammation. 

12. Deamidated Gliadin Peptide (DGP) antibodies, IgA

This blood test is used to identify the presence of Celiac disease. If your doctor is looking to rule out Celiac disease from the symptoms that you’ve listed, you’ll have the DGP antibodies (deamidated gliadin peptide) levels measures to see how many antibodies you have available in your blood. 

13. Anti-Endomysial Antibodies (EMA), IgA

EMA is another blood test that’s a routine test used to diagnose Celiac disease. Anti-Endomysial Antibodies are very similar to Anti-tTg antibodies. While they’re more sensitive, a blood test measures the application, significance, and usefulness of the endomysial antibodies in people with Celiac disease. 

14. Anti-Reticulin Antibodies (ARA), IgA

Retucluin is the connecting tissues that surround the majority of the organs in your body. Anti-reticulin antibodies can be found as a test for autoantibody screens. A positive test result for this antibody is an indicator of Celiac disease. This blood test can help your doctor to rule out the Celiac disease diagnosis or act as proof of the disease in your body.

15. Anti-Actin IgA (F-actin)

Anti-actin antibodies is another antibody that’s found in individuals with Celiac disease. The discovery of this antibody in your blood is predictive of the severity of your gluten sensitivity and is used as a tool to measure the severity of your Celiac disease (if you have it at all). 

16. Blood Culture

blood culture will let a doctor know if you have an infection, yeast, or parasites in your blood. A positive blood culture lets doctors know that you have bacteria or parasites in your blood. Depending on the infection or parasite that’s in your blood, many of the symptoms that your experiencing may direct your doctor away from an IBS diagnosis and towards the invader that was found in your blood. 

17. Urine Culture

urine culture will check to see if there’s any collagen degradation in your urine. Some studies have suggested that there’s an impairment of the elastic lining of the color, which impacts the function of the colon. By comparing urine samples from individuals with IBS to healthy individuals, the biomarkers that are measured in your use can help doctors to differentiate between ulcerative colitis and Crohn’s disease. 

18. Folate

Folate is a member of the B complex vitamin family and is responsible for working with Vitamin C to create new proteins. An adequate level of Folate in your blood is necessary for your body to produce white blood cells and red blood cells, repair cells, repair tissues, and is responsible for the synthesis of DNA.

19. Partial Thromboplastin Time (PTT, aPTT)

If your doctor suspects that your symptoms are related to your body having problems clotting your blood, they’ll order a partial thromboplastin time test. PTT is a blood test that measures the amount of time that it takes for your blood to clot. 

20. Prothrombin Time and International Normalized Ratio (PT/INR)

Another test that’s used to check to see if you have a potential bleeding disorder or an excessive clotting disorder. Prothrombin Time evaluates your body’s ability to clot blood. International Normalized Ratio is a calculate that’s made based on the results that PT showed about your body’s coagulation ability. 

21. H. Pylori

Helicobacter pylori is a type of bacteria that can enter your body and wreak havoc on your digestive tract. If left untreated, it can cause ulcers in the upper part of your small intestine, which could lead to a possible infection. A doctor will order this blood test to see if this unhealthy bacteria is present in your digestive tract. 

Taking Back Control of Your Health

Receiving an IBS diagnosis can help get you on the right path to receive the medical treatment that’s needed to improve your quality of life. Blood test results make it easier for your physician to properly diagnosis you while also sorting out other potential health problems that could be affecting you.

Are you looking to learn more about the key blood tests that are used to diagnose IBS? Click here to take a look at our available tests!