What is Giardia lamblia (Giardiasis)?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: May 9, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Giardia lamblia infection should be treated with tinidazole as the first-line option, as recommended by the 2017 Infectious Diseases Society of America clinical practice guidelines 1. Giardia lamblia is a microscopic parasite that causes the diarrheal illness known as giardiasis.

  • Treatment typically involves antiparasitic medications, with tinidazole (Tindamax) being the first-line option, or metronidazole (Flagyl) as an alternative 1.
  • For children, appropriate dosing is based on weight, and tinidazole is approved in the United States for children aged ≥3 years 1.
  • During infection, patients should stay well-hydrated and may need to temporarily avoid dairy products as lactose intolerance can occur.
  • Giardia spreads through contaminated water, food, or direct contact with infected feces, and prevention includes proper handwashing, drinking treated water, and careful food handling, especially when traveling to areas with poor sanitation.
  • The parasite attaches to the intestinal wall and reproduces, causing symptoms like watery diarrhea, abdominal cramps, nausea, and fatigue that typically appear 1-2 weeks after exposure and can last 2-6 weeks if untreated.
  • Diagnosis of Giardia infection can be made using a Giardia antigen test or polymerase chain reaction, which have excellent performance characteristics with sensitivity and specificity of >95% 1.
  • The AGA recommends testing for Giardia in patients presenting with chronic diarrhea, and modern diagnostic tests for Giardia have excellent performance characteristics 1.

From the FDA Drug Label

1 INDICATIONS AND USAGE

1.2 Giardiasis Tinidazole is indicated for the treatment of giardiasis caused by Giardia duodenalis (also termed G. lamblia) in both adults and pediatric patients older than three years of age [see Clinical Studies ( 14.2)] .

The treatment of giardiasis caused by G. lamblia is indicated for tinidazole in both adults and pediatric patients older than three years of age 2.

  • Key points:
    • Indication: Giardiasis
    • Causative agent: G. lamblia
    • Treatment: Tinidazole
    • Patient population: Adults and pediatric patients older than three years of age

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.