Fever is usually absent. Many persons with Giardia have no symptoms at all. Symptoms may begin 3 to 25 days after swallowing Giardia cysts, but usually within 10 days. Giardiasis is typically diagnosed by finding Giardia lamblia cysts in a stool sample submitted to a laboratory. Since cysts are intermittently passed in the stool, more than one specimen may be necessary to make the diagnosis because the cysts may not be in every stool specimen.
Some individuals recover from giardiasis without any treatment.
When therapy is necessary, antibiotics are often prescribed. The drugs currently used to treat giardiasis are effective in most but not all individuals, and relapses do occur. This may last from a few weeks to months. Anyone with diarrhea should remain home from work or school to minimize the risk of passing this infection on to others. In most cases, individuals may resume routine activities after the symptoms of illness have resolved.