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Giardiasis

  • Overview
  • Theory
  • Diagnosis
  • Management
  • Follow up
  • Resources
Last reviewed: 11 Aug 2025
Last updated: 03 Jan 2025

Summary

Definition

History and exam

Key diagnostic factors

  • diarrhea
  • frequent belching
Full details

Other diagnostic factors

  • abdominal bloating and discomfort
  • malaise
  • weight loss
  • nausea and vomiting
Full details

Risk factors

  • contaminated water/food
  • domestic animals living in or around the house
  • hypogammaglobulinemia
  • young age
  • male sex
  • day-care center attendance
  • oral-anal sexual contact
  • recent antibiotic use
Full details

Diagnostic investigations

1st investigations to order

  • direct fluorescence antibody (DFA) test
  • enzyme-linked immunosorbent assay
  • nucleic acid amplification test, polymerase chain reaction of stool sample
  • stool microscopy
  • CBC
Full details

Investigations to consider

  • Lateral flow immunoassay (e.g., ImmunoCard STAT!)
  • duodenal aspirates and biopsies
  • string test (EnteroTest)
Full details

Treatment algorithm

ACUTE

nonpregnant adult or child

pregnant; first trimester

pregnant; second or third trimester

ONGOING

treatment failure or resistance

Contributors

Authors

Luther A. Bartelt, MD

Assistant Professor of Medicine

University of North Carolina School of Medicine

Division of Infectious Diseases

Chapel Hill

NC

Disclosures

LAB is reimbursed by UpToDate for authorship. LAB has received funding from the National Institutes of Health. LAB is the author of two articles cited in this topic.

Acknowledgements

Dr Luther Bartelt would like to gratefully acknowledge Dr Fida Khan and Dr Musaddiq Waheed, previous contributors to this topic.

Disclosures

FK and MW declared that they had no competing interests.

Peer reviewers

Zana Nikolla, MD

Faculty of Medicine

University of Tirana

Tirana

Albania

Disclosures

ZN declares that she has no competing interests.

Rodney Adam, MD

Professor of Medicine and Immunobiology

University of Arizona

Tucson

AZ

Disclosures

RA declares that he has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Center for Disease Control and Prevention. CDC Yellow Book 2024: health information for international travel. Section 5: travel-associated infections & diseases - ​giardiasis. May 2023 [internet publication].Full text

Centers for Disease Control and Prevention. Giardia: about Giardia infections. May 2024 [internet publication].Full text

Shane AL, Mody RK, Crump JA, et al. 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea. Clin Infect Dis. 2017 Nov 29;65(12):e45-80.Full text  Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
  • Giardiasis images

  • Differentials

    • Rotavirus or other viral gastroenteritis
    • Functional diarrhea
    • Celiac disease
    More Differentials

  • Guidelines

    • CDC Yellow Book: health information for international travel - giardiasis
    • Infectious diarrhea: guideline for investigation
    More Guidelines

  • Patient information

    Diarrhea in adults

    More Patient information
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