Giardiasis

Medically reviewed by Drugs.com. Last updated on Apr 6, 2025.

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What is giardiasis?

Giardiasis, or giardia, is an infection of the intestines caused by a parasite. The Giardia parasite lives in the intestines of infected humans or animals. It is most often spread through direct contact. It can also spread through contaminated food or water.

What are the signs and symptoms of giardiasis?

Signs and symptoms of giardiasis usually appear within 2 weeks after exposure. You may have any of the following:

• Diarrhea
• Abdominal cramps and bloating
• Burping or passing gas more often than usual
• Weight loss or dehydration
• Nausea

How is giardiasis diagnosed?

A sample of your bowel movement is sent to a lab for tests. You may need to give up to 3 samples over several days.

How is giardiasis treated?

• Antibiotics: This medicine will help fight the infection.
• Antiparasitics: This medicine will help kill the parasite that is causing giardiasis.

Treatment options

The following list of medications are related to or used in the treatment of this condition.

• metronidazole
• Flagyl
• Flagyl 375
• Flagyl IV
• Alinia

View more treatment options

What are the risks of giardiasis?

You may develop lactose intolerance (cannot digest milk products). Without treatment, you can develop malabsorption (cannot absorb nutrients properly). You may become dehydrated. Severe dehydration can cause organ failure, which can be life-threatening.

How can giardiasis be prevented?

• Wash your hands often: Use soap and water. Wash your hands after you use the bathroom, change a child's diapers, or sneeze. Wash your hands before you prepare or eat food.
• Wait to have sex: Wait until your signs and symptoms are gone before you have sex. Use protection when you have sex.
• Drink safe water: Drink only sealed, bottled water or carbonated water. Do not drink water from streams, rivers, or lakes. Boil water or treat it with a chemical purifier to make it clean and safe.
• Handle food properly: Cook food to the proper temperature. Do not eat raw food. Wash your fruits and vegetables with clean water or peel them before you eat them.

Drugs used to treat this and similar conditions

How can I manage my symptoms?

• Drink liquids as directed: You may need to drink extra liquids to help prevent dehydration. Ask how much liquid to drink each day and which liquids are best for you. You may need an oral rehydration solution (ORS). An ORS has the right amounts of water, salts, and sugar your body needs.
• Eat a variety of healthy foods: Healthy foods include fruits, vegetables, whole-grain breads, low-fat dairy products, beans, lean meats, and fish. You may need to limit the amount of milk products or fat you eat. Ask if you need to be on a special diet.

What increases my risk for giardiasis?

• You live in a group setting, such as a college dorm or a nursing home.
• You have anal intercourse.
• You drink untreated water directly from streams, wells, or lakes.
• You travel to a country where drinking water is not purified.

When should I contact my healthcare provider?

• Your signs and symptoms last more than 1 week.
• You have questions or concerns about your condition or care.

When should I seek immediate care or call 911?

• You are dizzy and weak.
• You have a dry mouth, cracked lips, and feel thirsty.
• You have a fast heartbeat and are breathing fast.
• You urinate less than usual or not at all.
• You have severe abdominal pain or your abdomen is hard and swollen.
• You have black or bright red bowel movements.
• Your vomit has blood in it.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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