Last reviewed: September 2018
Last updated: July  2017



History and exam

Key diagnostic factors

  • presence of risk factors
  • symptoms after ingestion of dairy products
  • diarrhoea
  • distention
  • lethargy
  • mouth ulceration
  • headache
  • poor short-term memory
  • poor concentration
  • muscle/joint pain
  • eczema
  • failure to thrive

Other diagnostic factors

  • abdominal pain/discomfort
  • borborygmi
  • flatulence
  • skin rashes
  • palpitations
  • hx of asthma
  • hx of peptic ulcer disease
  • hx of GORD
  • nausea
  • vomiting
  • constipation
  • pallor
  • steatorrhoea
  • weight loss
  • short stature
  • progressive disability
  • flushing
  • sensory loss
  • oedema
  • hair loss

Risk factors

  • black, Native American, Asian, or Hispanic ethnicity
  • adolescence and early adulthood
  • FHx of lactase deficiency
  • enteritis/gastroenteritis
  • comorbid predisposing disease
  • hx of irritable bowel syndrome diagnosis

Diagnostic investigations

1st investigations to order

  • trial of dietary lactose elimination
  • FBC
Full details

Investigations to consider

  • lactose hydrogen breath test
  • stool culture
  • faecal pH
  • faecal reducing substance/sugar
  • lactose tolerance test
  • small bowel biopsy
Full details

Emerging tests

  • genotyping
  • 13C-labelled lactose breath test
Full details

Treatment algorithm


Authors VIEW ALL

Academic Neuro-Gastroenterologist

University College London

Consultant Gastroenterologist

University College Hospital and the National Hospital for Neurology and Neurosurgery (Queen Square)




AE declares that he has no competing interests.

Dr Anton Emmanuel would like to gratefully acknowledge Dr Mohammad Azam and Dr Richard J. Farrell, previous contributors to this monograph. MA and RJF declare that they have no competing interests.

Peer reviewers VIEW ALL

Assistant Professor of Medicine

Harvard Medical School

Beth Israel Deaconess Medical Center




AL declares that he has no competing interests.

Coordinator of the Gastrointestinal Motility Laboratory

University of Pavia

1st Division of Medicine

IRCCS S. Matteo Hospital Foundation




MDS is the author of references cited in this topic.

Use of this content is subject to our disclaimer