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Lactose intolerance test: how to understand if the body digests milk
Lactose intolerance is a condition in which the body cannot properly digest lactose, the sugar in milk. This can cause bloating, abdominal discomfort, gas, or loose stools after consuming milk or ice cream.
Many people avoid dairy for years without knowing the exact cause of their discomfort. That's why testing for lactose intolerance is important — it helps distinguish a true enzyme deficiency from a food allergy, irritable bowel syndrome, or a reaction to other foods.
Why does lactose intolerance occur?
Lactose is broken down by the enzyme lactase. If there is not enough of the enzyme, the lactose is not digested and begins to ferment in the large intestine.
The reasons may be different:
• genetic characteristics (the body naturally produces less lactase)
• age-related decrease in the enzyme
• foodborne infections or intestinal inflammation
• intolerance after acute illnesses
• consequences of celiac disease or malabsorption syndromes
Intolerance is rare in young children, but the prevalence increases with age.
Main symptoms to watch out for
Not all symptoms occur at the same time, but a typical set looks like this:
• bloating 30–120 minutes after milk
• bubbling, gases
• cramps or aching pain
• diarrhea or very loose stools
• nausea after dairy products
• an unpleasant feeling in the stomach after ice cream, milk, cream
Many people find relief by eliminating milk itself, but can tolerate yogurt or hard cheeses—an important diagnostic clue.
What tests exist?
Testing can be simple, non-invasive, or genetic, depending on the situation.
1. Hydrogen breath test
One of the most reliable. After taking lactose, the patient exhales into a special device that measures hydrogen levels. If the lactose is not broken down, the hydrogen levels increase.
Advantages: non-invasive, suitable for adults and children.
2. Blood test after lactose loading
The glucose level is measured after taking lactose. If the glucose does not increase, the enzyme is not enough.
Pros: fast. Cons: less sensitive.
3. Genetic test
Examines gene variants responsible for lactase production. Shows whether there is a hereditary predisposition.
It is well suited when symptoms are vague or you want to get an answer "once and for all".
4. Stool test (for toddlers)
Detects organic acids, a product of lactose fermentation. Most often used in young children.
Table: which test to choose
| Method | For whom | Best suited when |
|---|---|---|
| Hydrogen breath | adults, children | need an exact answer |
| Blood after lactose | adults | there are restrictions on the breath test |
| Genetic | all | suspicion of hereditary intolerance |
| Stool test | children under 3 years old | other methods are not available |
When to take the test
A doctor may recommend testing if:
• bloating or diarrhea regularly occurs after milk
• there is prolonged abdominal discomfort for no apparent reason
• diagnosed with irritable bowel syndrome, but symptoms worsen after eating dairy products
• there is a suspicion of an enzyme deficiency in the child
• have had an intestinal infection and the symptoms have not disappeared
The check will help you avoid self-imposed strict diets and improper restrictions.
How to prepare for the test
The preparation is quite simple, but important:
• come on an empty stomach (6–12 hours without food)
• do not drink alcohol during the day
• do not accept probiotics 3–5 days
• avoid physical exertion before the test
• do not smoke on the day of the examination
• do not eat cabbage, legumes, carbonated drinks for 24 hours
Proper preparation ensures accurate results.
What to do after diagnosis
Once lactose intolerance is confirmed, the patient can:
• choose products with low lactose content
• use lactase enzyme (as recommended by a doctor)
• replace milk with lactose-free milk
• include fermented milk products in the diet, which are often well tolerated
• work with a dietitian if symptoms persist
Lactose intolerance does not mean that you need to completely eliminate dairy products - the main thing is to find the amount and form that suits your body.
The lactose intolerance test is simple, informative, and helps you understand whether your symptoms are related to milk. Correct diagnosis allows you to avoid unnecessary restrictions, choose a comfortable diet, and regain control over your well-being. The sooner you determine the cause of your discomfort, the sooner you can restore normal functioning of your digestive system.
