This site is intended for health professionals only

At the heart of general practice since 1960

pul jul aug2020 cover 80x101px
Read the latest issue online

Independents' Day

How to improve management of lactose intolerance

Dr John Leeds and Dr David Sanders provide 10 tips that might improve a GP's management of this condition

Dr John Leeds and Dr David Sanders provide 10 tips that might improve a GP's management of this condition


Lactose intolerance comes in many forms and each responds to different degrees of therapy. Lactose intolerance is due to primary, secondary, congenital or developmental lactase deficiency. Primary lactase deficiency presents usually in infanthood and congenital lactase deficiency is rare. Secondary lactase deficiency can occur at any age whereas developmental lactase deficiency occurs in pre-term infants and improves as the gastrointestinal tract matures.


Symptoms depend upon age and may mimic other conditions. Classical symptoms are abdominal cramps, bloating, flatulence and diarrhoea after taking milk or dairy products. Diarrhoea is said to be more common in the young and hydration needs to be carefully monitored. In some children, lactose intolerance may lead to reduced growth and needs to be considered as a cause. Adults may present with irritable bowel syndrome with a specific intolerance to dairy products.


Secondary lactose intolerance is common. Secondary lactose intolerance is due to loss of brush border enzymes in conditions where there is damage to the small intestine or enteropathy. Exclusion of conditions such as coeliac disease by a duodenal biopsy should therefore be considered. Secondary lactose deficiency may occur following gastrointestinal infection and should be expected to improve with time. Infants who are being breastfed should not stop in these circumstances as continued nourishment and hydration is crucial. Antibiotic therapy is often given unnecessarily.


Involvement of a dietitian may be helpful in preventing dietary imbalance. Dairy products, especially milk, are the main source of dietary calcium and exclusion from the diet entirely may increase the risk of metabolic bone diseases such as osteoporosis and fracture. Some dairy products are better tolerated than others and combination with other foodstuffs may allow reintroduction of dairy products into the diet.


Medications often contain lactose but not usually enough to cause symptoms. Patients may worry excessively about lactose in medications, but the amount of lactose in the majority of medications is not sufficient to cause symptoms. Unless the medication is essential, then a short trial of either reduced dose or stopping can be used, but beware the placebo effect.


Complete lactose withdrawal is not always needed. Some people with lactose intolerance can tolerate small amounts of lactose spread throughout the day as symptoms appear to relate to the rate and volume of fluid delivered into the colon. Cheese and yoghurt may be easier to reintroduce as the lactose may be reduced during preparation and the rate of delivery into the small intestine is slower. Combination with cereal has been shown to be well tolerated in children.


Lactose intolerance is genetic and recessive. Lactase deficiency is less common in Europeans than other ethnic groups. Therefore in patients with relevant features, ethnicity is also important. Lactose intolerance occurs in around one-quarter of Europeans, about half of Hispanics, Afro-Caribbeans, south Indians and Ashkenazi Jews, but almost all Asians.


A number of laboratory tests exist but none is 100% sensitive. The lactose tolerance test has poor sensitivity (75%). The lactose hydrogen breath test has a higher sensitivity (90%) but requires specific equipment to perform. There has been interest recently in the quick lactase test, which is performed on duodenal biopsy specimens and measures lactase activity directly, but this is clearly much more invasive. The diagnosis is therefore often made on clinical grounds.


Treatment of primary lactose intolerance depends upon clinical symptoms. Patients should be encouraged to slowly increase daily milk intake as the colon can adapt to higher lactose volumes over time. Similarly to tip 4, combination with other foodstuffs, such as cereal, can help with increasing dairy product intake.


Most patients can be diagnosed and treated in primary care. As the diagnosis is largely clinical and the treatment dietary, referral to a specialist or use of advanced testing is most often not required. Those who may benefit from referral to secondary care are patients with poor or no response to dietary measures, those in whom the diagnosis of secondary lactase deficiency requires exclusion, in cases of diagnostic uncertainty or in the presence of other more alarming symptoms such as severe weight loss, PR bleeding and persistent severe diarrhoea.

Dr John Leeds is honorary clinical lecturer in gastroenterology and Dr David Sanders is consultant gastroenterologist and honorary reader, University of Sheffield

Competing interests None declared

micrograph of lactose crystals in milk lactose crystals

Rate this article 

Click to rate

  • 1 star out of 5
  • 2 stars out of 5
  • 3 stars out of 5
  • 4 stars out of 5
  • 5 stars out of 5

0 out of 5 stars

Have your say