What is lactose intolerance?

The small intestine normally makes lactase, an enzyme that breaks lactose into smaller sugars. If lactase is low, undigested lactose passes into the large intestine, where bacteria create gas and draw in fluid. This may cause abdominal cramps, bloating, wind and diarrhoea after dairy foods or drinks.

Tolerance varies. Some people react to larger portions but manage small amounts with meals; yoghurt or hard cheese may be easier for some people than milk. Lactose intolerance is not the same as a milk allergy, which can cause hives, breathing difficulty or swelling.

Keep a food and symptom diary for several days, noting the product, portion and time symptoms begin. Avoid making broad, long-term restrictions without advice, because dairy can contribute useful calcium and protein. A healthcare professional may discuss a structured dietary trial, suitable alternatives or [Food Intolerance Testing](/treatments/diagnostics-and-screening/food-intolerance-testing/).

Read labels for milk, lactose, whey and milk powder. [Nutrition Counselling](/treatments/lifestyle-and-wellness/nutrition-counselling/) can help you plan balanced meals. You can read more about [Lactose Intolerance](/conditions/lactose-intolerance/) and related symptoms such as [Bloating](/symptoms/bloating/).

Arrange an assessment if symptoms are new, persistent, worsening, or happening without dairy. Seek urgent help for breathing trouble, throat or facial swelling, faintness, severe pain, blood in stool, repeated vomiting or signs of dehydration. Diarrhoea or abdominal pain that continues should not automatically be blamed on lactose.

Ask what pattern would support lactose intolerance, whether another condition should be considered, and how to meet calcium needs if you reduce dairy. Show your food diary and any medicines or supplements.