Eat bland foods (bananas, rice, toast, boiled potatoes)
Avoid dairy products for 4 to 6 weeks as lactose intolerance is common after infection
Avoid fatty or spicy foods until diarrhea resolves
Infection prevention and public health
Hand hygiene
Wash hands thoroughly with soap and water after bathroom use and before food preparation
Alcohol-based hand sanitizers do not kill Giardia cysts; soap and water required
Water safety
Boil or filter water when camping, hiking, or traveling to endemic areas
Do not drink untreated surface water or well water of unknown quality
Exclusion from work and school
Food handlers must not return to work until 24 to 48 hours after starting treatment
Children in daycare should be excluded until diarrhea has resolved
Notifiable disease
Giardiasis is a reportable condition; the clinic or hospital will notify public health
Follow-up instructions
Routine follow-up
Follow up with your doctor in 5 to 7 days to confirm symptom improvement
A repeat stool test is only needed if symptoms persist after treatment
Household contacts
Household members with similar symptoms should see a doctor
Test and treat symptomatic household contacts
Return to emergency department
Return immediately for any of the following
Worsening or persistent diarrhea beyond 7 days after starting treatment
Signs of severe dehydration: dizziness, fainting, dry mouth, no urination for 8 hours
Bloody diarrhea or black stools
High fever (temperature > 38.5 degrees Celsius or 101.3 degrees Fahrenheit)
Inability to keep any fluids down
Severe abdominal pain or worsening abdominal pain
Yellowing of the skin or eyes (jaundice)
References
Guidelines and key sources
American Family Physician guidelines
Pyzocha N, Cuda A. Common Intestinal Parasites. American Family Physician. 2023. PMID 37983700
Covers epidemiology, diagnosis, and treatment of Giardia and other intestinal parasites
Source of drug dosing tables and diagnostic test performance characteristics
IDSA Infectious Diarrhea Guidelines
Shane AL, Mody RK, Crump JA, et al. 2017 IDSA Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea. Clinical Infectious Diseases. 2017. PMC5850553
Recommendations on stool testing indications (Choosing Wisely criteria)
O&P testing guidance for < 7 day diarrhea in immunocompetent patients
Cochrane systematic review on drug treatment
Granados CE, Reveiz L, Uribe LG, Criollo CP. Drugs for Treating Giardiasis. Cochrane Database of Systematic Reviews. 2012
Comparative efficacy of nitroimidazoles for giardiasis
Disulfiram reaction data for metronidazole and tinidazole
Network meta-analysis comparative efficacy
Ordonez-Mena JM, McCarthy ND, Fanshawe TR. Comparative Efficacy of Drugs for Treating Giardiasis. Journal of Antimicrobial Chemotherapy. 2018. PMID 29186570
Systematic update and network meta-analysis of randomized clinical trials
Adam RD. Giardia Duodenalis: Biology and Pathogenesis. Clinical Microbiology Reviews. 2021. PMID 34378955
Trophozoite adhesion mechanisms and mucosal damage pathways
Villous blunting and brush border enzyme disruption
Dixon BR. Giardia Duodenalis in Humans and Animals. Research in Veterinary Science. 2021. PMID 33066992
Zoonotic transmission including beaver and domestic animal reservoirs
Long-term sequelae
Miko S, Kache PA, Imada E, Freeland AL, Haston JC. Postinfectious Syndromes and Long-Term Sequelae After Giardia Infections. Emerging Infectious Diseases. 2025. PMID 41570191
Approximately one-third of patients with long-term extraintestinal symptoms
Ocular, muscular, and metabolic complications data
Pediatric and HIV guidelines
Kapogiannis BG, Yates F, Li W, et al. Guidelines for the Prevention and Treatment of Opportunistic Infections in Children With and Exposed to HIV. Office of AIDS Research Advisory Council. 2025
Giardia as cause of traveler's diarrhea and post-travel persistent diarrhea
Water treatment recommendations for travelers
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.