Giardia Infection: Causes, Symptoms, and Treatment
Medically reviewed by Sumiran Racherla, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Giardia Infection?
A primary care doctor, who handles general health care, can treat Giardia infection. An infectious disease doctor, a doctor who treats illnesses caused by germs, is another specialist for this infection. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is Giardia infection?
Giardia infection is an illness caused by a tiny parasite called Giardia. Doctors also call the illness giardiasis.
The parasite also goes by the names Giardia duodenalis, Giardia lamblia, and Giardia intestinalis.
It lives in the gut of infected people and animals. It leaves the body in poop. It can survive for weeks to months outside the body, such as in soil. It is found in every region of the United States and around the world.
Symptoms
Diarrhea is the main symptom. Symptoms usually start 1 to 2 weeks after you become infected. They often last 2 to 6 weeks. Some people have no symptoms at all. Occasionally, people have symptoms that last for years.
Common signs include:
- Diarrhea, often 2 to 5 times a day.
- Gas, bloating, and smelly, greasy poop that can float.
- Stomach cramps or pain.
- Upset stomach or nausea.
- Headache, loss of appetite, and a low-grade fever.
- Feeling more and more tired.
- Weight loss and loss of body fluids.
Complications can include dehydration, which means losing too much water and fluid, and malabsorption, which means the body does not absorb nutrients well.
Causes and who gets it
You can get sick when you swallow Giardia. Giardia germs are in poop. Food, water, surfaces, and objects that get contaminated with poop can spread the germs. Swallowing just a few germs can make you sick.
You are more likely to get sick if you:
- Drink untreated water from springs, lakes, rivers, or shallow wells.
- Swallow water from pools, lakes, or rivers while swimming.
- Are in an area with limited access to safe drinking water.
- Travel to a country where giardia is common.
- Are in close contact with someone who is sick, especially in child care settings.
- Eat raw or undercooked food that has been contaminated with the parasite.
- Have a weakened immune system.
- Have contact with poop during sex.
- Have contact with infected animals or animal environments contaminated with poop.
How doctors diagnose it
If you think you may have Giardia, contact a healthcare provider. The provider will ask for stool samples. Stool means poop. Doctors may use these tests:
- A stool antigen test, which checks the stool for giardia.
- A stool polymerase chain reaction (PCR) test, which can detect several germs, including giardia.
- A stool ova and parasites exam, a lab check of stool for parasites.
You often need to give several stool samples for testing.
Treatment
If there are no symptoms or only mild symptoms, no treatment may be needed. Some infections go away on their own within a few weeks.
Antibiotic treatment is successful for most people. An antibiotic is a medicine that fights germs. Doctors may prescribe tinidazole, nitazoxanide, or metronidazole. If symptoms do not go away, a change in the type of antibiotic will be tried.
If you have diarrhea, drink a lot of water or other fluids to avoid dehydration, which means losing too much fluid.
Some of these medicines can cause side effects, including a metallic taste in the mouth, nausea, and a severe reaction to alcohol.
In most pregnant women, treatment should not start until after delivery. Some medicines used to treat the infection can be harmful to the unborn baby.
People who take water pills, also called diuretics, may need to stop them during this illness. Follow your doctor's instructions. Never stop any medicine without first talking to your health care provider.
When to see a doctor
Contact your provider if diarrhea or other symptoms last more than 14 days, if you see blood in your stool, which is unusual, or if you are dehydrated.
Call 911 or go to the emergency room if you faint, are confused or very hard to wake, or have severe belly pain or severe vomiting that does not stop.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either one can evaluate symptoms and arrange the stool tests used to diagnose giardia infection.
Common questions
Is Giardia infection contagious?
Yes. Giardia can spread from one person to another, especially among people in close contact in child care settings. It can also spread through contaminated water, food, surfaces, and objects.
How long does Giardia infection last?
Symptoms usually last 2 to 6 weeks. Occasionally, people have symptoms that last for years. Some people have no symptoms at all.
Can you get Giardia from a pet?
It is unlikely. The type of Giardia that makes people sick is usually not the same type that makes dogs and cats sick.
How can you avoid getting Giardia?
You can lower your risk by washing your hands with soap and water at key times. Avoid swallowing water while swimming. Boil or filter water from lakes, springs, or rivers before drinking or preparing food with it. Peel or wash fresh fruits and vegetables before eating them. Avoid touching animal poop. Wait to have sex for several weeks after you or your partner no longer have diarrhea.
Sources
- MedlinePlus - Giardia Infections
- Centers for Disease Control and Prevention - About Giardia Infection
- MedlinePlus Medical Encyclopedia - Giardia infection
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
