First Time User? Enroll now.
COVID-19: Vaccine information, visitor restrictions, testing, treatment, and additional resources
Home > Health Library > Giardiasis
Giardiasis (say "jee-ar-DYE-uh-sus") is an infection of the intestines caused by the parasite Giardia lamblia. The illness is also called giardia (say "jee-AR-dee-uh"). It can happen if you drink water that has been contaminated.
You may become infected with giardia if you eat food or drink water that is tainted with infected human or animal waste.
In the United States and Canada, you can get giardia by drinking untreated water from wells, streams, rivers, and lakes. This is true even in mountain lakes and streams where the water may seem very pure.
You can also get the infection if you swallow contaminated water while you swim.
You can get giardia from someone else through:
After a person is exposed to the parasite, it usually takes 7 to 10 days for the infection to develop. But it can take from 3 to 25 days or longer. You can pass the infection to others during the entire time you are infected. You may be infected for months, even if you don't have symptoms.
Giardiasis can cause diarrhea, stomach cramps, gas, and nausea. You may feel sick once and then get better. Or your symptoms may come and go for some time. Some children with giardiasis don't grow or gain weight normally. Sometimes giardiasis doesn't cause any symptoms.
To diagnose giardiasis, your doctor will test your stool for the parasite that causes the infection. Your doctor will also ask questions about your past health and do a physical exam.
In some cases, you may be tested for giardiasis even though you don't have any symptoms. For example, this could happen during an outbreak at a day care center.
If you have symptoms, your doctor may prescribe medicine to kill the parasite. It's important to take the medicine for as long as prescribed, so the infection doesn't return.
You can manage your symptoms at home.
Some people with giardiasis have temporary trouble digesting milk and milk products (lactose intolerance). If you have this problem, avoid these foods for at least 1 month. Then slowly add them back into your daily meals as your body can handle them.
If you don' t have symptoms, there is usually no treatment. But your doctor may give you medicine to lower the chance that you will pass the infection to others.
There are some things you can do to avoid giardiasis.
Current as of:
July 1, 2021
Author: Healthwise StaffMedical Review: E. Gregory Thompson MD - Internal MedicineAdam Husney MD - Family MedicineW. David Colby IV MSc, MD, FRCPC - Infectious Disease
Current as of: July 1, 2021
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine & W. David Colby IV MSc, MD, FRCPC - Infectious Disease
To learn more about Healthwise, visit Healthwise.org.
© 1995-2022 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.