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"How can I know if I'm lactose intolerant? Is there a test for it?"

ZocdocAnswersHow can I know if I'm lactose intolerant? Is there a test for it?


I often experience discomfort on my stomach with certain irritant foods but how do I know if I'm lactose intolerant or have irritable bowel syndrome? Thanks.


Thank you for your question. I recommend that you schedule an appointment with your primary care doctor for a proper evaluation, but here are some ways to distinguish lactose intolerance from irritable bowel syndrome (IBS). Lactose intolerance is caused by a lack of the enzyme lactase, which is required to break down lactose carbohydrate molecules in the GI tract. When lactose is not broken down, it causes bloating, flatulence, crampy abdominal discomfort, and diarrhea. This always occurs after consuming lactose-containing foods (such as milk, cheese, ice cream, etc.). A simple way to diagnose this is to avoid lactose and see if the above symptoms resolve. If there is any question, a test called the "hydrogen breath test" can be performed to definitively diagnose lactose intolerance. IBS, on the other hand, is defined as abdominal pain that is associated with at least 2 of the following 3 features: pain relief with defecation, change in stool frequency, and/or change in stool form (diarrhea or constipation). These symptoms must occur over at least a 3 month period to meet the criteria to diagnose IBS. If you are noticing symptoms with certain foods, other possibilities to consider include celiac disease, GI tract infections, and small bowel bacterial overgrowth. Consultation with your primary care physician is the first step in figuring out the cause of your symptoms and getting you to feel better!

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