People with primary lactose intolerance (the common inherited form) should find out how much lactose they can handle, by gradually building up the amount they eat. People do have varying levels of intolerance. Sometimes the amount they can tolerate can be increased by giving milk or dairy products little and often. Having milk with meals may help. Full-fat or chocolate milk may be better than skimmed milk. Thicker foods such as yoghurts and curds are likely to be better tolerated because they move through the bowel at a slower rate. Live yoghurts and hard cheese (such as Cheddar, Edam, Emmental or Parmesan) may not cause problems. Lactose-free milks are available but may be less nutritious than cow's milk. Check they are calcium-enriched. It is possible to buy lactase supplements at health food shops, to be taken with dairy products. However, these may be expensive and cannot be prescribed.

Secondary lactose intolerance, due to damage to the lining of the gut (small intestine), is usually treated by stopping dairy products for a short time, depending on the age of the child. Babies and very young children are dependent on milk for their nutrition, and it will not be possible to stop it even for a short time. If the diarrhoea is very severe, occasionally treatment by fluid through a drip may be needed. Most doctors advise parents of babies and children with gastroenteritis to carry on with breast milk, formula milk or cow's milk. In some cases if the diarrhoea is very prolonged, or in very young babies, some doctors recommend withdrawing lactose for three weeks after the infection. Lactose-free formula milk is available for severe cases but is not usually needed.

The chance of premature babies getting lactose intolerance due to developmental lactase deficiency can be reduced by feeding them half-strength lactose formula or breast milk.