Are you currently living with an unexplained chronic health condition that medical professionals haven’t yet diagnosed? Do you have a number of unexplained symptoms that no matter the treatment, you haven’t felt better?


(often misdiagnosed as Chronic Fatigue Syndrome,
Irritable Bowel Syndrome and even Depression)

These are all symptoms of Giardia.  However, fatigue seems to be the most prevalent among cases.  During the past two decades, the parasite Giardia Lambia has become recognized as one of the most common causes of waterborne disease (drinking and recreational) in humans in the United States.

2.5 million cases of giardiasis occur each year in the United States, and up to 20% of the world’s population are chronically infected. Two-thirds of infected people may present asymptomatically or are misdiagnosed with such conditions as Chronic Fatigue Syndrome, Irritable Bowel Syndrome and even Depression. This organism is found in roughly 25% of the cases of gastrointestinal disease.

The statistics of people walking around with this infection are astounding.  Yet, when I shared my diagnosis with family, friends and even acquaintances, nobody ever heard of it.  Why was that? 

15% of people who swallow cysts are asymptomatic.  These cases can be detected if the person’s stool is tested during a community outbreak.  This is significant because people who carry the cysts in their digestive tract, known as carriers, can still transmit giardiasis to others even if they do not develop the symptoms of the illness.  

Without my diagnosis, my husband would have never found out he too was infected.  It was not confirmed whether he walked around with the infection for as long as me.  Was he asymptomatic the whole time or was I the source of transmission at some point during my condition?  If this was true, then millions of people with or without chronic conditions may be continuously spreading giardia unbeknownst to them. 

The CDC concluded that the burden and cost of acute giardiasis in the United States was substantial and that hospitalizations resulting from this condition cost approximately $34 million each year.  This is a public report, yet why are hospitals not testing for giardia? 

During all my emergency room visits, I was told the hospital could only deal with my acute problem at hand, providing enemas to relieve my constipation. Whether a patient complains of diarrhea or constipation, if the hospital used a valid giardia test, the rectal swap, this infection can be diagnosed within twenty-four hours and people receive antibiotics to avoid further chronic issues. If some of these uncertainties and questions were addressed, people would no longer have to worry about their own drinking water, and water in general.  If our country implemented studies on this parasite, and the effects it has on people and the environment, we could make changes and offer prevention.

FAQ: Frequently Asked Questions

Click on each of the questions below to expand the answer.

Giardia Lamblia is a protozoan parasite.  Protozoan means one cell.  

There is an adult form of Trophozoite (if you looked at a picture it looks like a smiling face and tail).  That form has the flagellin and moves around and is what makes a person sick.

The Trophozoan can form a cyst, (it’s little and oval shaped – it’s smaller than the Trophozoite and has a shell around it).  It also is one cell and you can only be seen under a microscope.  The cysts of giardia can live outside the body, but the Trophozoites will die quickly if outside of a dog or a human.  The cysts can live on surfaces up to 15 days.  

For example, a bathroom doorknob, handle or faucet can have cysts, which come from drinking water.  The giardia cysts are also found in streams and rivers due to sewage contamination or delivered via beavers and other animals. People who backpack in the wilderness need to treat all water for giardia.

People can start to get sick within three to ten days.  However, a person doesn’t necessarily feel the impact of major symptoms because of the low load of giardia cysts; however, the parasite starts growing when signs of stress appear in other areas of the body.


The most common way a person gets infected is by consuming food or water that is contaminated.  A food handler can contaminate the food.  Sometimes giardia is spread within families because someone has giardia and is the person preparing the food for their family.

Public restroom facilities

Open salad bars are a perfect example of a situation in which raw food sitting on an open table with many different people handling the food with tools.  A reporter, who noticed people’s behavior around open salad bars, documented this example.

Sex, especially oral sex.

Household pets (dogs and cats) can carry giardia.  If you are cleaning up after your pets, the cysts of giardia can get on your hands.  Pets are grooming themselves and are licking their skin (the perianal and genital areas of skin).  Just handling your pet may transfer giardia.

Children going to daycare centers. As many as 30% of daycare staff are infected with giardia annually, especially in infant centers because of the diaper changing.  Horizontal surfaces at infant care centers carry giardia and need to be carefully wiped with Clorox to help get rid of it.

  1. Acute diarrhea, gas, bloating, nausea and fatigue

A lot of people acquire and have no symptoms at all.  An asymptomatic giardia carrier can spread giardia to someone else and that person can become symptomatic.  There are different strains of giardia, so it is possible that some are pathogenic while others are not. In some family situations, it is clear that their is one person who had no symptoms who brought the infection into the family but only other family members got sick so they must have gotten sick with same strain.  

In general, women tend to be more prone to contracting giardia than men, which possibly has to do with hormones.

  1. Chronic: constipation may be more prominent then diarrhea, gas, bloating, fatigue nausea, abdominal pain, and an intolerance of specific foods (fruit in particular).

When you treat giardiasis, food problems will resolve slowly.  There are other unusual symptoms associated with giardia that do not depend on a compromised immune system and they are probably due to the nature of the immune response triggered by giardia, including skin rashes, hives and joint pains.

Giardia can also cause an overgrowth of bacteria and yeast in the small intestine.  The bacteria and yeast that overgrow may ferment food to produce substances that have toxic effects.  Some people have neurological effects (brain fog and spaciness related to eating) when infected. 

It means symptoms have been going on for more than a few months. According to Dr. Leo Galland, once treated properly, people with symptoms present for more than 25 years could be cured within a year.

Irritable Bowel Syndrome, Chronic Fatigue Syndrome, or depression.  As far as hormones come into play, since women tend to be more affected than men and some women find the symptoms are cyclic and relate to their menstrual cycle, there are definitely hormonal influences on the symptoms.

Any kind of chronic infection can disrupt a person’s hormones, but it is still undecided if giardia does that more than any other kinds of infections.

The main effect of a compromised immune system is that it increases susceptibility to acquiring giardia and makes it much harder to get rid of. 

The concept of a compromised immune system is very tricky.  The damage that’s associated with giardia in the intestines is actually due to your own immune system.  

There was a study done on animals that had certain aspects of their immune system disabled and their intestines were not damaged by giardia.  It’s the immune system itself that damages the intestines and produces symptoms like hives and arthritis with giardia. You need a strong immune system to get rid of giardia and not get sick.  However, when you do get sick, the disturbed immune system contributes to symptoms. 

The immune system is such a complex set of reactions (it’s really like an orchestra, not a radio that you turn the volume up or down).  There are all these different parts that interact in different ways to produce the desired outcome to fighting an infection.  There are many people in whom this modulation does not occur properly for many reasons, one being related to different kinds of stress. It’s been well documented that someone can be a carrier of giardia and not have any symptoms and then get really stressed, whether psychological or an acute infection, or given steroids to treat something and giardia becomes active, because whatever is going on (in particular the steroids) dampen down the immune response in such a way that giardia gets activated.  AIDS is a situation in which people are prone to giardia and other intestinal parasites.  Another example that is not a direct effect of the immune system but that increases susceptibility to giardia, is lack of stomach acid so people taking drugs like proton pump inhibitors to treat heartburn may increase your susceptibility.

There are two types of tests a person can take.

Standard test is a stool test. Stool is examined by using special stains looking for the presence of the giardia antigen and is also examined after being concentrated to see if you can see cysts or Trophozoites.  The problem with stool testing is that it misses many cases of giardia.  A single stool test will only pick up 50 percent of cases and multiple stool tests will still miss 10 percent, even in acute giardiasis. Another test used is called a rectal swab test.  There are very few physicians that do this test.  Even tropical medicine specialists don’t necessarily do it.  Aside from Dr. Kevin Cahill, there may be a few parasitologists who do this test.  With a rectal swab, rectal mucus is taken and examined directly, instead of taking a stool specimen.  It’s not likely to pick up Trophozoites because giardia is an infection in the small intestine, but it is a place where you can often find the cysts of giardia.  Stool testing in regular hospital laboratory or the standard national diagnostic labs may find infection but often come up with false negatives.

Any doctor can order this test but you want a laboratory that specializes in tropical medicine or Parasitology.  There are doctors who specialize in that as well.

Several different drugs are used to treat giardiasis.  The original antibiotics prescribed were Flagyl or Metronidazole (although found there are resistant strains to Metronidazole now).  

There is a newer drug related to Metronidazole called Tinidazole or Tindamax.  This medicine is shown to be superior to Flagyl and causes fewer side effects.  

The newest drug available is Alinia, which is Nitazoxanide.  It’s easy to take, has fewer side effects and seems to be more effective.  Albenza is mostly used to treat worms, but when used in conjunction with Alinia or Tinidazole, it enhances the effect of the drug.  Doctors may use a combination of Alinia or Albendazole to treat giardiasis, especially in chronic cases or if the person has failed previous treatments.  

There are some things that can enhance the effectiveness of the drugs.  One that’s studied most is a yeast, called Saccharomyces Boulardii, which is available under the trade name, Florastor.  It’s been shown in a study of children in Bangladesh to cure giardia by itself without any drugs.  It’s helpful for preventing antibiotic induced diarrhea and enhances effectiveness of anti parasitic drugs (when its administered with them) and these drugs do not kill Florastor because it is a yeast, not a bacterial probiotic.  

There are a number of herbs that may be used occasionally or as follow-up to antibiotics but haven’t been tested in same control trials that antibiotics have been studied.  They include: grapefruit extract, citrus seed extract and Berberine, which were derived from several different kinds of herbs.  Berberine and Artemisia or its extract called Artemisnin, is mostly used in treating Malaria but has been helpful in treating giardia especially in combination.  Some doctors use the three herbs especially as follow-up to antibiotics.  

Side effects depend on the medication.  Metronidazole can produce a metallic taste in your mouth, abdominal pain, fatigue, numbness, tingling in your arms and legs, mood changes and confusion.  Not a good first choice.  Tinidazole may produce all of the same symptoms but much less likely to do so.  Side effects with Alinia and Albenza are quite rare and mostly cause abdominal pain, which is also true with Florastor.  Some people who are allergic to yeast will break out in skin rashes and it tends to be constipating.

This varies greatly from case to case.  Sometimes a person can be better while on a drug within a few days.  Often it can take a week or so before noticing improvement because the drugs are so rough.  Occasionally, improvement doesn’t manifest itself for at least a few weeks.  Some people may feel better in the beginning of treatment but then can backtrack and feel worse again.  There may not be stable improvement for several weeks or even a few months after treatment is complete.  

Dr. Leo Galland studied a phenomenon called Leaky Gut Syndrome, which is measured by doing a test for Small Intestinal Permeability.  Results to this test usually show up abnormal in those who have giardiasis because there is a lot of inflammation in the small intestine.  In some cases, after the person is cured it can take between 6 to 9 months to feel normal.

If after treatment you still have intestinal symptoms or any symptoms, its possible that you have a bacterial or yeast overgrowth in the intestines that wasn’t covered by the medication prescribed. If this is the case, it needs to be treated.

Diet may have a significant impact on your symptoms.  It may take months, a year or even longer before you are able to eat a normal diet after having giardia.  People who have giardia or who have had giardia are often sensitive to sugar.  Sugar in fruits as well as in sweets, alcohol and wheat.  Eliminating the foods is worthwhile once you find out if eating them aggravates your symptoms.  Since giardiasis is often associated with bacterial or yeast overgrowth, further dietary changes may help.  One is a yeast and mold avoidance diet and the other is Fructose Malabsorption Diet. You can even go to the extreme with the FODMAPS Diet.  It came from Australia and is related to the diet of the Fructose Malabsorption. 

There may also be Nutritional Supplements that are needed because people with giardia can get deficient in Vitamin A and B12.  If you’ve been treated for giardia and appear to be cured but some symptoms still exist, one of the important things to consider is getting tested for Small Intestinal Bacterial Overgrowth.  Family members should be tested as well.