Last Updated August 2022 | This article was created by editorial staff and reviewed by Kyle Bradford Jones

What is giardiasis?

Giardiasis is an infection you can get in your small intestine. It is caused by a microscopic parasite called Giardia lamblia. Once you have been infected with the parasite, it lives in your intestines. It is passed along through feces (poop). Anything that comes in contact with feces from an infected person or animal can become contaminated. Giardiasis is one of the main causes of diarrhea in the United States. It can be found all around the world.

Symptoms of giardiasis

Diarrhea is the main symptom of giardiasis. Other symptoms include:

  • Bloating
  • Intestinal gas
  • Abdominal cramps
  • Nausea
  • Loss of appetite
  • Low-grade fever
  • Weight loss and loss of body fluids

Symptoms usually appear 1 to 3 weeks after exposure to the parasite. Although these problems can be very unpleasant, the illness isn’t usually dangerous.

What causes giardiasis?

The Giardia parasite lives all over the world in soil, food, and water. It also can live on surfaces that have come into contact with human or animal waste. You could be infected if:

  • You drink untreated water in nature. Many animals carry giardia in their feces. They may introduce the parasite into rivers, streams, or lakes. Infected stream water may look clean and safe when it really isn’t.
  • Your city water became infected through sewer line flooding or leaking.
  • You travel to a place that doesn’t boil or treat their water.
  • You swallow water while swimming or playing in a lake, river, or stream.
  • You are exposed to another person who has giardiasis.
  • You eat raw or undercooked food that is contaminated with the parasite.
  • You have unprotected anal sex with a person with the parasite.

Some people who get giardiasis don’t become ill. But they can still spread the parasite to other people. Giardiasis may be easily spread in daycare centers or nursing homes. It is important that workers wash their hands each time after changing diapers or helping someone go to the bathroom.

How is giardiasis diagnosed?

To diagnose giardiasis, your doctor will want to you to provide stool (poop) samples to the lab. The lab will look at the samples under a microscope. Several samples may have to be checked before the diagnosis can be made. Sometimes other tests may be necessary.

Can giardiasis be prevented or avoided?

Giardiasis can be prevented in many cases. The best ways to avoid it are:

  • Be very careful about the water you drink. Don’t drink water from rivers, lakes, or streams.
  • When camping, take bottled water or boil water before you use it.
  • Wash your hands carefully with soap and water several times a day.
  • When traveling, don’t brush your teeth or wash dishes with water that hasn’t been boiled.
  • Peel raw fruits and vegetables before you eat them.
  • Don’t eat undercooked food.

If one person in your family gets giardiasis, it’s likely that everyone in your home will get it, especially children. Hand washing is very important to help prevent the illness from spreading.

Giardiasis treatment

If your symptoms are mild, you generally won’t need treatment for giardiasis. Mild infections can go away on their own in a few weeks. If symptoms are severe or aren’t going away, medicine can be used. Infected people who work at a daycare or nursing home may also be treated with medicine. This can help prevent the illness from spreading.

There are many medicines that can be used to treat giardiasis. One of the most common is called metronidazole. It’s usually taken 3 times a day for 5 to 10 days. Side effects may include a metallic taste in the mouth, nausea, and a severe reaction to alcohol. It is safest for pregnant women to avoid this treatment. Children younger than 5 years of age may be treated with furazolidone. This medicine has fewer side effects and comes in a liquid form.

Giardiasis spreads very easily. It’s usually best if a whole family is treated at the same time. In most cases, your doctor will want to check a stool sample after the treatment to be sure the medicine worked. Sometimes you may need to take medicine for a longer time. Or your doctor may want you to take another medicine for a complete cure.

It is important to treat for dehydration when you have giardiasis. Pregnant women and infants are more likely to get dehydrated when they have diarrhea. Dehydration can be fatal for infants. Talk to your doctor about treatment options if your baby has giardiasis.

Living with giardiasis

Call your doctor if you have diarrhea, bloating, and nausea for more than a week. Giardiasis is unpleasant, but it’s not usually dangerous. Once you begin the medicine, you can recover in about a week. If it’s left untreated, symptoms can last 6 weeks or more.

As with any illness, complications can occur. These include:

  • Dehydration – losing too much water and other fluids in your body.
  • Malabsorption – when the intestinal tract doesn’t absorb enough nutrients from your food.
  • Weight loss – excessive diarrhea can cause you to lose too much weight too fast.

Call your doctor if you’ve been treated for giardiasis but are experiencing any of these symptoms.

Questions to ask your doctor

  • My family is going camping. How can we prevent giardiasis?
  • What should I do if I think I have giardiasis?
  • Do water filters prevent giardiasis?
  • Are there medicines that prevent giardiasis? Is there a vaccine for giardiasis?
  • What medicines treat giardiasis? Are there side effects?
  • My water comes from a well. Should I have my well water tested?
  • Can I get giardiasis from my pet?