Lactose is a type of sugar found in milk and almost all dairy products. For lactose to be digested by the body, the body needs an enzyme known as lactase, produced by the small intestine. When the body cannot properly break down lactose, it is said that the person suffers from lactose intolerance.
To determine if a person is intolerant to this type of sugar, it is necessary to carry out a series of medical check-ups, among which the oral lactose tolerance test stands out, a medical test that allows us to know the ability of the intestines to break down the lactose through lactase. Continue reading this FastlyHealarticle and learn how to prepare for an oral lactose tolerance test and what the expected results are.
What is the oral lactose tolerance test?
When we consume any dairy or food containing lactose, our body orders the intestines to metabolize and break down this type of sugar, which is possible thanks to the production of the enzyme lactase. Lactase makes it possible for lactose to break down into two substances: glucose and galactose. Therefore, when for some reason, this process is not carried out, the consumption of lactose, which is a type of sugar, does NOT raise blood glucose levels. This picture is enough to diagnose a person as lactose intolerant.
The oral lactose tolerance test is done precisely to determine how the body behaves during a concentrated intake of this sugar and if the intestines can metabolize it. To carry out this test, a fasting blood sample is taken to determine glucose concentration in the blood. Then, the person is given a juice high in lactose, and after ingesting said drink, the blood is drawn every 30 or 60 minutes again, depending on the doctor’s instructions. The ideal is to verify that after said lactose ingestion, the glucose levels increased. Otherwise, the person is considered intolerant.
The oral lactose tolerance test can last up to three hours and is explicitly prescribed to diagnose lactose intolerance. Although it does not usually cause side effects, there are people who, during the test, have moderate pain when drawing the blood. After drinking lactose concentrate, some experience stomach pain, nausea, and dizziness. If you suffer from needle phobia, it is necessary to discuss it with the bioanalyst before the first blood draw.
Preparation for the oral lactose tolerance test
- Eat healthy the week before the exam to prevent excess food from interfering with glucose values.
- You must attend the clinical laboratory on an empty stomach, that is, without eating or drinking anything for 10 hours.
- The only allowed intake is water.
- It would help if you did not eat or drink anything during the test.
- You should not do any exercise 8 days before the test.
- Talk to your doctor about the medications you usually take to see if you should stop any of them to prevent them from interfering with the test results.
Normal and abnormal results
Normal test values
The oral lactose tolerance test is considered normal when the glucose level rises more than 30 ml / dL during the two hours following the ingestion of the lactose concentrate. If glucose increases by 20 ml / dL, the result is not considered conclusive. Average glucose values can vary according to the measurement scale used by each laboratory; for this reason, the doctor must interpret the results.
Abnormal test values
The abnormal result diagnoses a person as lactose intolerant. The oral lactose tolerance test is considered abnormal when glucose values rise by less than 20 ml / dL within two hours of ingesting lactose concentrate. If the test is weird, it is also necessary to perform an oral glucose intolerance test to rule out that the lactose test has failed due to a deficit in the body to absorb sugar.
Lactose intolerance
When the body cannot properly break down lactose, the person has specific symptoms 3 minutes after consuming this type of sugar. Symptoms include:
- Abdominal cramps
- Abdominal distension.
- Diarrhea.
- Gases.
- Sickness.
Premature babies are at higher risk of developing lactose intolerance; they can even be intolerant to breast milk consumption. Lactose intolerance can also occur in adulthood. People most at risk for this condition are:
- Black people.
- Adults of Asian, African, and Native American descent.
- People who have suffered from any condition in the small intestine compromise the production of the enzyme lactase. Some diseases that can injure the intestines are celiac disease and Crohn’s disease .
Reducing the intake of dairy or lactose products is essential to improve the symptoms of intolerance to this type of sugar. There are drinks such as beer that contain lactose without being considered dairy; for this reason, it is advisable to read the labels of all foods and products to verify that they are lactose-free. People with lactose intolerance are prescribed oral consumption of the lactase enzyme through lozenges or chewable tablets not to suspend dairy intake and avoid calcium and vitamin D deficiencies. Opt for the consumption of lactose-free dairy products. Oatmeal or almond milk can also be an alternative.
This article is merely informative, at FastlyHeal .com we do not have the power to prescribe medical treatments or make any type of diagnosis. We invite you to see a doctor in the case of presenting any type of condition or discomfort.
If you want to read more articles similar to Oral Lactose Tolerance Test, we recommend that you enter our Digestive System category .

I am a Surgeon with a diploma in comprehensive ultrasound and surgical care residency, an area I am specializing in. During the exercise of my profession, I have realized the need for patients to know the diseases they suffer, and I can tell you that a large part of their complications is due to a lack of information. Being a health web writer allows me to transmit my experience, without borders, to all those readers eager for knowledge, educate them in the prevention of diseases and promote a healthy lifestyle.