Digestive intolerances: lactose, fructose, sorbitol, lactulose
27/03/2026
30 days before (1 month) taking the test, it is important that:
- You have not undergone any bowel cleansing or colonoscopy
- You have not received antibiotic therapy, aspirin, prokinetics, laxatives or enemas.
The test lasts approximately three hours. During this time, you must remain at rest in the laboratory waiting room.
The day before the test, you must follow a diet low in fermentable carbohydrates.
The test lasts approximately three hours. During this time, you must remain at rest in the laboratory waiting room.
The day before the test, you must follow a diet low in fermentable carbohydrates.
What can I eat?
- Water, unsweetened herbal infusions, tea
- Boiled white rice, without sauce, onion or garlic
- Eggs
- Meat, white or oily fish
- Unprocessed cured meats, such as Serrano or Iberian ham
What can’t I eat?
- Dairy products and derivatives, such as milk, yoghurts and cheese
- Soft drinks or sparkling water
- White or brown sugar, sweeteners
- Fruit or fruit juices
- Nuts
- Cereals, such as bread, biscuits and toast
- Pastries or bakery products, sweets, chewing gum, candies and jams
- Legumes, potatoes, vegetables and greens
- Processed cured meats, such as cooked ham, mortadella, fuet or salami
The test must be performed while fasting for 12 hours.
30 minutes before and during the test: do not smoke, do not perform any physical effort and do not brush your teeth in the morning.
A baseline breath sample will be collected. You will then be given a preparation containing lactose, fructose or sorbitol, depending on the type of test being performed. Breath samples will be collected every 25 minutes until the three hours are completed.