2016-06-16 18:42:32 UTC

Food Allergies and Intolerances 103: Getting Tested for Lactose Intolerance

View PDF Copy PDF Link



Lactose intolerance can be hard to figure out based just on symptoms. A gastroenterologist can use tests to find out if you’re lactose intolerant:


Lactose Breath Test 


  • Given to older children as well as adults.*
  • This test measures the amount of hydrogen in the breath. This test is very accurate.
  • In the test, the patient drinks a lactose-loaded drink, and the breath is tested at routine intervals.
  • Hydrogen in the breath means improper digestion of lactose. 
  • Certain foods, medications and smoking can change the test’s accuracy and may need to be skipped before the test.


Stool Acidity Test 


  • Used for infants and young children.
  • This test, which measures the amount of acid in the stool, has no risk to young children. 
  • This test is not very specific.


Lactose Tolerance Test 


  • This test is not often used. This test may be performed if the lactose breath test is not available.
  • Given to older children as well as adults.* 
  • Before the test, patients do not eat, and blood is taken to measure the fasting blood-sugar level. 
  • Patients then drink a large amount of a liquid that has lactose.
  • Blood samples are taken over a two-hour period, which tell how well the body is able to digest lactose.

* The lactose tolerance and hydrogen breath tests are not given to infants and young children, because giving these patients a lactose load can result in diarrhea (loose stool), which can cause dehydration.


Food Allergies and Intolerances – What to Know:
  • It is important to know the differences between food allergies and food intolerances.
  • A food allergy is a sudden, urgent and severe reaction to a food when it is eaten or touched. Symptoms include feeling itchy or having trouble breathing.
  • A food intolerance, or sensitivity, often has less severe symptoms, though is still very uncomfortable. Symptoms include gas and cramping pain.
  • Do not get rid of anything from your diet until your doctor tells you to do so.

© AGA, September 2017

©AGA, July 2016

More on Food allergies/intolerances

Attend the AGA Postgraduate Course for Practical, Take Home Information

Feb. 12, 2018

Join us on June 2-3 in Washington, D.C. This course is held in conjunction with Digestive Disease Week® (DDW) 2018.

The Lowdown on the Low-FODMAP Diet

Nov. 1, 2017

As the low-FODMAP diet grows in popularity, know the facts to help answer patient questions and provide guidance.

AGA-Funded Research Highlighted by The Atlantic

May 23, 2017

AGA Research Scholar Award recipient Dr. Lebwhol’s study brings science to the gluten-free craze.