Lactose Intolerance
Also known as Lactase deficiency
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is lactose intolerance?
Lactose intolerance is the inability to fully digest lactose, the sugar in milk, because of reduced lactase enzyme in the small intestine. Undigested lactose is fermented by gut bacteria, producing bloating, wind and diarrhoea. It is not a milk allergy and is not dangerous, though calcium intake needs attention if dairy is restricted.
Causes
- Genetically programmed decline in lactase after childhood
- Temporary lactase loss after gastroenteritis
- Damage to the small intestine from coeliac or Crohn disease
- Rare congenital lactase deficiency
Symptoms
- Bloating and abdominal distension
- Excess wind
- Abdominal cramps
- Diarrhoea
- Nausea
- Symptoms beginning 30 minutes to 2 hours after dairy
- Severity related to the amount consumed
Risk factors
- East Asian, West African, Arab, Jewish or Native American ancestry
- Increasing age
- Recent gastrointestinal infection
- Coeliac disease or inflammatory bowel disease
- Premature birth for transient deficiency
Diagnosis
- Symptom response to a trial of lactose exclusion and reintroduction
- Hydrogen breath test after a lactose load
- Lactose tolerance blood test
- Coeliac serology to exclude an underlying cause
- Distinguishing from cow milk protein allergy
Treatment
- Reducing rather than eliminating lactose in most people
- Lactase enzyme supplements taken with dairy
- Lactose free milk and dairy products
- Hard cheeses and live yoghurt, which are often well tolerated
- Ensuring adequate calcium and vitamin D intake
- Treating any underlying gut condition
Self care
- Reduce rather than eliminate lactose, since most tolerate some
- Take dairy with meals, which improves tolerance
- Try hard cheeses and live yoghurt, which are lower in lactose
- Use lactase enzyme supplements before dairy meals
- Choose lactose free milk and dairy products
- Ensure adequate calcium and vitamin D from other sources
When to see a doctor
Book an appointment if:
- Symptoms continuing despite avoiding lactose
- Weight loss or blood in the stool
- Symptoms starting suddenly in adulthood
- Concern about calcium intake
- A child with poor growth and digestive symptoms
- Before adopting a fully dairy free diet long term
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Primary lactose intolerance cannot be prevented
- Secondary intolerance is reduced by treating the underlying gut condition
- Reintroduce dairy gradually after gastroenteritis
- Maintain calcium intake to protect bone health
Outlook
Lactose intolerance is harmless and easily managed. Most people find a tolerance threshold that allows normal eating with minor adjustments. Secondary intolerance after gastroenteritis or gut inflammation usually recovers within weeks to months once the underlying cause is treated.
Common questions
Is lactose intolerance the same as milk allergy?
No. Lactose intolerance is a digestive enzyme issue causing discomfort. Cow milk allergy is an immune reaction to milk protein that can cause rashes, wheeze and, rarely, anaphylaxis, and it requires strict avoidance.
Must all dairy be avoided?
Usually not. Most people tolerate around 12 grams of lactose, roughly a glass of milk, especially with food. Hard cheese and live yoghurt contain little lactose and are often fine.
How is calcium maintained without dairy?
Through fortified plant milks, tinned fish with bones, tofu set with calcium, leafy greens and nuts, with supplements if intake remains inadequate. Bone health matters, particularly for women.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.