Digestive symptom

Chronic diarrhea and your gut: which markers and tests to look at

Chronic diarrhea (loose or watery stools more than three times a day, lasting more than four weeks) has more potential drivers than almost any other gut symptom. The microbiome contributors split roughly into three groups: (1) active infections (parasites like Giardia or Cryptosporidium, opportunistic bacterial overgrowth), (2) inflammatory drivers visible as elevated Calprotectin or Lactoferrin, and (3) bile acid malabsorption or pancreatic insufficiency, both detectable on tests that measure Steatocrit and Pancreatic Elastase-1. A stool test rules in or out the infectious and inflammatory categories quickly, which is the highest-value first step.

See a doctor first if you have any of these

blood or mucus in stool
night-time bowel movements that wake you up
fever
unintended weight loss
diarrhea lasting more than two weeks

These symptoms warrant clinical evaluation before any food protocol. The rest of this page assumes you've ruled them out.

The gut markers most often behind chronic diarrhea

Ordered by how frequently they appear in the literature for this symptom. Click any underlined marker to see what the result means and how to address it.

1
Elevated Calprotectin
2
Lactoferrin (detail page coming soon)
3
Positive Blastocystis hominis
4
Elevated Candida species
5
Low Faecalibacterium prausnitzii
6
Pancreatic Elastase-1 (detail page coming soon)
7
Steatocrit / Fecal Fat (detail page coming soon)

Tests best suited to find them

Listed in priority order. Tests with PDF upload support get you a full personalized protocol the same day you upload.

Diagnostic Solutions Laboratory · Upload supported GI-MAP Genova Diagnostics · Upload supported Genova GI-Effects Doctor's Data Doctor's Data GI360

Already have a stool test PDF?

Upload your GI-MAP, Genova GI-Effects, or Biomesight result and we'll extract every marker behind your chronic diarrhea and generate a personalized 6-week food protocol with exact quantities.

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Non-gut causes worth ruling out first

Chronic diarrhea is not always gut-driven. Before assuming the cause is in your microbiome, work through these:

lactose, fructose, or sorbitol malabsorption
inflammatory bowel disease (IBD) — Crohn's or ulcerative colitis
celiac disease (independent of stool test findings, get tTG-IgA blood work)
thyroid hyperfunction
certain medications (metformin, magnesium, antibiotics, SSRIs)

Low-cost things to try this week

These are reasonable first moves while you decide whether to test or wait. None of them require a prescription or a kit.

Replace electrolytes daily (sodium, potassium, magnesium)
Cut artificial sweeteners and sugar alcohols (sorbitol, mannitol, erythritol)
Try cutting dairy for 2 weeks as a lactose probe
Get a celiac panel if you have not already, even if you eat gluten-free

Frequently asked questions

Is chronic diarrhea always caused by gut problems?

No. The gut connection is real and often underdiagnosed, but the page above lists non-gut causes worth ruling out first. Going straight to a stool test without considering thyroid, anemia, sleep, or medication side effects can mean treating the wrong thing.

Which test is best for chronic diarrhea?

The recommended tests above are listed in priority order. The general rule: GI-MAP and Genova GI-Effects are the higher-yield choices when the suspected drivers are infections, opportunistic overgrowth, or host-marker patterns. 16S sequencing tests like Biomesight or Thorne are better for diversity and ecology questions.

How long until I see improvement once I start a protocol?

Symptom-level changes usually appear within 2 to 3 weeks of starting a targeted dietary protocol. Marker-level changes take longer, typically 8 to 12 weeks, which is the validated retest window for most stool-test panels.

Can I skip the test and just try a generic protocol?

You can. The trade-off is that chronic diarrhea has multiple possible drivers and the food protocols differ between them. A test costs less than 6 to 12 weeks of trying the wrong protocol. If budget is the constraint, the lowest-cost meaningful test in this category is Biomesight (around $130 to $180).

When should I see a doctor instead of self-investigating?

The red flags listed above are the cases where a doctor visit comes first. Anything else is reasonable to investigate with a stool test, but a doctor visit in parallel with the gut work is almost always the right move when symptoms are persistent.