Within one to two weeks after becoming infected, Giardia symptoms usually occur. Common symptoms of infestation include diarrhea, bloating, vomiting, and abdominal pain. In otherwise healthy people, symptoms generally last two to six weeks. People who experience recurring symptoms or whose symptoms of Giardia never completely go away may have a condition called chronic giardiasis.
When a person becomes infected with the parasite that causes giardiasis (Giardia lamblia), the parasite begins to multiply within the intestines. After one to two weeks (the average is seven days), Giardia symptoms can occur. This period between becoming infected and the start of symptoms is known as the "Giardia incubation period."
Symptoms of Giardia may begin gradually or come on all of a sudden. In addition, they often vary among individuals. Some people may be infected with Giardia but have no symptoms; other people may experience severe symptoms.
Giardia infection can cause a variety of intestinal symptoms. Common ones include:
- Gas or flatulence
- Abdominal (stomach) pain
- Greasy stools that tend to float
- Stomach cramps
- Upset stomach or nausea.
These Giardia symptoms may lead to weight loss and dehydration.
In otherwise healthy people, symptoms may last two to six weeks. The diarrhea can improve after a week or so. Occasionally, Giardia symptoms last longer. These people may have chronic giardiasis.