The simplest method is pure self-observation that the quantity of milk and dairy products consumable previously without a problem gradually reduces.

Professional, medical methods are the following, which, however, should be carried out only by certified doctors:

  • Lactose stress test with subsequent measurement of the blood sugar levels
  • Lactose stress test with subsequent measurement of the concentration of hydrogen in the air exhaled (H2 breath test)
  • Genetic test

The lactose stress test (alternatives one and two) is generally conducted by specialists for internal medicine and specialists in gastroenterology. You are given a specific quantity of lactose dissolved in water to drink (25 – 50 g) on an empty stomach, and thereafter, a blood sample or a breath sample (in the case of the 2 breath test) is collected in regular intervals. Since, in the case of human beings having lactase deficiency, the lactose is not or only slightly converted into glucose and galactose, no or only a small amound of glucose can be reabsorbed in the small intestine and discharged into the blood. Hence, the consumption of a test meal containing lactose by human beings having lactase deficiency results in only a slight or no increase in the glucose level (blood sugar level), whereas for those not having any lactase deficiency, the glucose level would rise more significantly. Thus, based on the trend of the blood sugar level, it can be established whether the person suffers from lactase deficiency. If the lactose that cannot be reabsorbed gets into the large intestine, it is broken down there by the intestinal bacteria with the formation of hydrogen (H2) among others. The hydrogen is reabsorbed by the intestinal wall and reaches the lungs via blood circulation, from where it is then exhaled. Thus, based on the content of hydrogen in the exhaled air, it can be established whether lactose, which has not been broken down in the small intestine, reaches the large intestine. In the event of lactase deficiency, the hydrogen content of the exhaled air after the consumption of a lactose test meal will increase, whereas in the case of human beings who do not suffer from lactase deficiency will not increase.

The genetic test represents a new method, but is not paid by the medical health insurance companies and costs about 70,– €. You merely need to send a smear of the buccal mucosa to a certified laboratory and specialised for this investigation. The genetic test merely indicates whether you develop a primary lactase deficiency in the course of your life or not. Hence, even a positive test result does not mean that primary lactase deficiency is already present. You can establish this only with the help of the lactose stress test described above (alternatives one and two).