Lactose Tolerance Test

The Lactose Tolerance Test measures your body’s ability to break down lactose, a type of sugar found in milk and other dairy products.This test measures the amount of glucose produced when lactose breaks down. If lactose is incompletely broken down, the blood glucose level does not rise and a diagnosis of lactose intolerance is confirmed.

How Long Will It Take?

The lactose tolerance test itself takes approximately 2 hours to complete, however you will need to allow time for the registration process and for the pharmacy to prepare your lactose solution.  You should expect to be at the hospital for approximately 2.5 to 3 hours.

Patient Preparation

• You should fast for 8 hours.
• Avoid strenuous exercise for 8 hours prior to the test.
• Feel free to bring a book, or something else to keep you occupied during the test.

How the Test is Performed

• Upon arriving at the hospital, you will need to check in at Registration.
• Registration will direct you to the Outpatient Lab, where you will be asked to have a seat in the waiting room while the pharmacy prepares your lactose solution.  You may be asked to provide your weight as the lactose dose is weight dependant.  
• Once your lactose solution is ready, you will have a fasting blood draw.
• You will be asked to drink the lactose solution as quickly as possible but within a 5 minute time frame.
• After the lactose dose has been administered, you will be drawn at 15, 30, 60 and 120 minutes.  During the test, you will have a total of 5 blood draws.

While you wait for your next blood draw, you will be asked:

• To remain on hospital grounds.
• To remain inactive.
• To not smoke or chew gum.

What Do the Results Mean?

• Normally blood glucose levels rise more than 20 mg/dl above the baseline level within 2 hours of ingestion of the lactose dose.
• The failure of blood glucose levels to rise as expected confirms the diagnosis of lactose intolerance.  
• If your test results are abnormal, your doctor may request a glucose tolerance test to rule out a glucose absorption problem.
• You should be receiving the results from your doctor within two weeks of test performance.