To help diagnose giardiasis, your doctor is likely to test a sample of your stool. For accuracy, you may be asked to submit several stool samples collected over a period of days. The samples are then examined in a laboratory for the presence of parasites. Stool tests may also be used to monitor the effectiveness of any treatment you receive.
Children and adults who have giardia infection without symptoms usually don't need treatment unless they're likely to spread the parasites. Many people who do have problems often get better on their own in a few weeks.
When signs and symptoms are severe or the infection persists, doctors usually treat giardiasis with medications such as:
- Metronidazole (Flagyl). Metronidazole is the most commonly used antibiotic for giardia infection. Side effects may include nausea and a metallic taste in the mouth. Don't drink alcohol while taking this medication.
- Tinidazole (Tindamax). Tinidazole works as well as metronidazole and has many of the same side effects, but it can be given in a single dose.
- Nitazoxanide (Alinia). Because it comes in a liquid form, nitazoxanide may be easier for children to swallow. Side effects may include nausea, flatulence, yellow eyes and brightly colored yellow urine.
There are no consistently recommended medications for giardiasis in pregnancy because of the potential for adverse drug effects to the baby. If your symptoms are mild, your doctor may recommend delaying treatment until after the first trimester. If treatment is necessary, discuss the best available treatment option with your doctor.
Preparing for your appointment
While you may initially bring your symptoms to the attention of your family doctor, he or she may refer you to a gastroenterologist — a doctor who specializes in disorders of the digestive system.
What you can do
Before your appointment, you may want to write a list of answers to the following questions:
- When did your signs and symptoms begin?
- Does anything make them better or worse?
- Do you work or live with small children?
- What types of medications and dietary supplements do you take?
What to expect from your doctor
During the physical exam, your doctor may ask you to lie down so that he or she can gently press on various parts of your abdomen to check for tender areas. He or she may also check your mouth and skin for signs of dehydration. You also may be given instructions about how to bring in a sample of your stool.
Oct. 23, 2018
- Leder K, et al. Epidemiology, clinical manifestations, and diagnosis of giardiasis. https://www.uptodate.com/contents/search. Accessed Sept. 1, 2015.
- Munoz FM. Treatment and prevention of giardiasis. https://www.uptodate.com/contents/search. Accessed Sept. 1, 2015.
- Levinson W. Intestinal and urogenital protozoa. In: Review of Medical Microbiology and Immunology. 13th ed. New York, N.Y.: The McGraw-Hill Companies; 2014. https://accessmedicine.mhmedical.com. Accessed Sept. 1, 2015.
- Giardia. Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/giardia/. Accessed Sept. 1, 2015.
- Longo DL, et al., eds. Protozoal intestinal infections and trichomoniasis. In: Harrison's Principles of Internal Medicine. 19th ed. New York, N.Y.: The McGraw-Hill Companies; 2015. https://accessmedicine.mhmedical.com. Accessed Sept. 1, 2015.
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Giardia infection (giardiasis)