What should you know about lactose intolerance tests?

A clinician usually starts with your symptom pattern, dairy intake, timing and medical history. A hydrogen or methane breath test can measure gases made when unabsorbed lactose reaches bowel bacteria. Another approach is a planned lactose reduction followed by reintroduction, with symptoms recorded carefully. Blood testing may be used in some settings. These approaches assess lactose digestion; they are different from tests for milk-protein allergy. [Lactose Intolerance](/conditions/lactose-intolerance/) can cause [Bloating](/symptoms/bloating/), cramps, gas and [Diarrhoea](/symptoms/diarrhoea/) after dairy.

Before an appointment, record dairy foods, portions, symptoms and how long they last. Ask the service whether you need to fast or change medicines before a breath test. Avoid using several new supplements or cutting out many foods at once, because that can make the pattern difficult to interpret. If lactose reduction helps, reintroducing a measured amount can show whether symptoms return. [Food Intolerance Testing](/treatments/diagnostics-and-screening/food-intolerance-testing/) may be discussed when the history is unclear. A dietitian or [Nutrition Counselling](/treatments/lifestyle-and-wellness/nutrition-counselling/) can help maintain adequate nutrition.

Seek urgent care for severe or worsening [Abdominal Pain](/symptoms/abdominal-pain/), repeated vomiting, blood in stool, faintness, breathing trouble or swelling around the mouth. Book a review when symptoms persist despite avoiding lactose, disturb sleep, cause dehydration, reduce food intake or come with unexplained weight loss. Those features may point beyond lactose intolerance and should not be settled by home testing alone.

Ask which assessment fits your symptoms, whether you need to test for another bowel condition, how to reintroduce lactose safely, and which calcium-rich alternatives suit your diet.