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Giardia Symptoms: What Every Hiker Needs To Know

By Diane Spicer

Giardia symptoms are unpleasant, and potentially life threatening if they debilitate you while on a backcountry hiking trip.

Once these symptoms hit you, you'll have to suffer through them until you can begin a treatment protocol.

Here's what you need to keep yourself out of trouble.

What is giardia?

Giardia is the shorthand name for a microscopic trouble maker named Giardia intestinalis. You might also hear it called G. lamblia or G. duodenalis, depending on where you get your information.

This parasite with the clunky name lurks in surface water, and will reproduce itself in your intestines if you are unfortunate enough to swallow it.

How did it get into the lake or stream in the first place?


A mammal defecated in the water, and now you're the lucky owner of a new generation of Giardia.

Which mammals harbor Giardia?

For hikers, it's the critters which inhabit the habitat you're hiking through:

  • Beavers (hence the nickname beaver fever)
  • Deer
  • Humans

You can pick up giardia in any region of the world, so if you're planning a backpacking trip anywhere, you need to pay attention to your water purification methods.

And I say methods -plural - for a reason.

Don't rely on just one way to get clean hiking water.

Read up on backpacking water purification methods here.

Always have a backup plan, because staying hydrated is just that important.

  • For fast, light hiking water purification gear, rely on a Lifestraw Go.
  • Read my review here.

And never tell yourself that cold water can't be contaminated.

These giardia parasites love, love, love cold water and will persist for many months in water that looks absolutely clear and clean.

Winter mountain stream flowing throw snow covered banksCold water will not protect you from giardia symptoms if an infected mammal has pooped in the water, even many months ago.

Giardia symptoms
come on fast

The fancy way of saying that is "acute" symptoms, which are anything but cute:

  • Bloating and gas;
  • Increased frequency and quantity of stool (diarrhea);
  • Cramping in your abdominal region;
  • Weird greasy "floater" stools;
  • Disturbed gastrointestinal system functioning, including vomiting and "upset stomach" (nausea).

Here's the dangerous thing

Acute giardia symptoms set you up for dehydration, which in turn makes you dizzy, weak and unable to think straight.

  • You can't keep losing fluids from both ends (to be blunt) without getting into trouble with your heart beat and muscle contractions.

Also, the pain and discomfort from gas, bloating and cramps will take your mind right off staying safe on the trail, leading to trouble.

The longer these symptoms continue, the more fat you will lose from your digestive tract (because it's going into those weird stools), and hence the less energy you have available for hiking.

These giardia symptoms can linger for a week or two, making a long backpacking trip or thru hike virtually impossible.

They take about a week to develop after you ingest the contaminated water, so it's tough to know exactly which water source was the problem.

Giardia might also play hide and seek: the symptoms go away and you think everything is back to normal but no such luck when they come roaring back.

Oddly, some people ingest the giardia parasite and have absolutely no symptoms!

Go figure :(

How to prevent giardia symptoms from ruining your hiking plans

You can't go hiking without ingesting water to replace what you lose via breathing hard, perspiring, urinating and defecating.

That's just the way it is for those of us living in a human body.

But you can be smart about how you guarantee the safety of your hiking water.

If you haven't read the information about backpacking water purification and safety above, here are the links again:

Hiking water

Staying hydrated

Waterborne illnesses important to hikers

Backpacking water purification methods

And if you really want to dig into what the giardia parasite can do to your digestive system, read this!

Don't play fast and loose with your hiking water, because not only will it ruin your hiking plans, the parasite could stick around and cause you trouble again and again.

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Waterborne Giardia Symptoms