How to Get Tested for C. diff When Your Stool Raises Concern

Clostridioides difficile (C. diff) is a bacterium that can cause diarrhea and more serious intestinal conditions. If your stool appearance has changed—becoming loose, watery, foul-smelling or containing mucus—you may wonder whether you need testing for C. diff. This guide will explain when and how to get tested, what to expect from the lab, and next steps.

Understanding C. diff and Stool Appearance

C. diff produces toxins that irritate the colon lining. Typical stool changes include:

• Loose, watery diarrhea (three or more unformed stools in 24 hours)
• Greenish, foul-smelling stool
• Presence of mucus or sometimes blood
• Crampy abdominal pain

These signs don’t always mean C. diff, but they suggest you should seek medical advice—especially if you’ve recently taken antibiotics or spent time in a healthcare setting.

When to Consider Testing

You may consider C. diff testing if all of the following apply:

• You have unformed, watery diarrhea (≥3 episodes in 24 hours).
• Symptoms began during or shortly after antibiotic use, or after a hospital stay.
• You notice associated symptoms such as mild fever, cramping or nausea.

Risk factors that raise suspicion:

• Recent antibiotics (especially clindamycin, fluoroquinolones, cephalosporins)
• Hospitalization or nursing-home residence
• Advanced age (over 65)
• History of C. diff infection

If you’re unsure whether your symptoms meet these criteria, consider a free, online symptom check, using the doctor approved Ubie Symptom Checker to help you decide whether to seek immediate care.

Steps to Get Tested

1. Speak with a Healthcare Provider

   • Your primary care doctor, urgent care clinician or gastroenterologist can evaluate your symptoms and risk factors.
   • Be prepared to describe your stool appearance, frequency of diarrhea, recent antibiotic use, and any abdominal pain or fever.

2. Sample Collection

   • You’ll need to provide a fresh stool specimen. Most labs ask for an unformed (liquid) sample collected in a clean, dry container.
   • Collect at least 5–10 mL (roughly a couple of tablespoons) of stool.
   • Avoid contamination with urine or toilet paper.

3. Testing Methods
   Modern laboratories use one or more of the following tests:

   • Glutamate dehydrogenase (GDH) antigen test
     • Screens for the C. diff organism.
     • Highly sensitive but not specific for toxin-producing strains.

   • Toxin enzyme immunoassay (EIA)
     • Detects toxins A and B directly in stool.
     • Quick (results in hours), but less sensitive than molecular tests.

   • Nucleic acid amplification test (NAAT)/PCR
     • Detects toxin-producing genes.
     • High sensitivity and specificity.

   • Two-step or three-step algorithms
     • Combines GDH + toxin EIA, with PCR confirmation for discordant results.

4. Where to Get Tested

   • Hospital laboratory (if you’re currently admitted).
   • Outpatient laboratory (via your provider’s order).
   • Urgent care or walk-in clinic (they’ll send your sample to a partner lab).

5. Turnaround Time

   • Rapid EIA results: 1–4 hours.
   • PCR/NAAT results: 24 hours or less.

Interpreting Test Results

• Negative GDH + Negative Toxin: C. diff unlikely.
• Positive GDH + Positive Toxin: Active C. diff infection likely.
• Positive GDH + Negative Toxin (discordant): PCR may be performed to confirm.
• Positive PCR alone: Suggests a toxin-producing strain; correlate with symptoms.

Your healthcare provider will interpret results alongside your clinical presentation. A positive result in someone without symptoms may represent colonization rather than active disease; treatment isn’t always required in that setting.

Next Steps After Testing

If your test is positive, your doctor may recommend:

• Starting anti-C. diff antibiotics (e.g., vancomycin, fidaxomicin)
• Adjusting or stopping other antibiotics if possible
• Ensuring adequate hydration and electrolyte balance
• Monitoring for complications such as dehydration or toxic megacolon

If your test is negative but diarrhea persists, your provider may:

• Test for other causes (viral, parasitic, medication-induced)
• Recommend supportive care (hydration, diet adjustments)
• Order further imaging or endoscopy for abdominal pain

When to Seek Immediate Help

Contact your doctor or go to the emergency department if you experience:

• Severe abdominal pain or distension
• Blood in your stool or black, tarry stool
• High fever (over 102 °F/39 °C)
• Signs of dehydration (dizziness, very dark urine, rapid heartbeat)
• Confusion or lethargy

These could signal complications requiring urgent care.

Tips for Sample Collection at Home

• Collect stool sample before starting C. diff treatment, if possible.
• Follow lab instructions regarding refrigeration or transport time.
• Label the specimen container clearly with your name, date and time of collection.
• Wash your hands thoroughly after collection.

Preventing Transmission

C. diff spores can survive on surfaces for months. To reduce spread:

• Wash hands with soap and water (alcohol-based sanitizers are less effective against spores).
• Clean bathroom and high-touch surfaces with bleach-based cleaners.
• Launder bedding and towels in hot water.
• If you’re in a healthcare setting, follow contact-precautions (gown and gloves).

Final Thoughts

Recognizing suspicious stool appearance and acting promptly can help your healthcare team diagnose or rule out C. diff quickly. Early testing and appropriate treatment reduce the risk of complications.

If you’re uncertain about your symptoms or whether to get tested, try a free, online symptom check, using the doctor approved Ubie Symptom Checker. It’s a helpful way to clarify your next steps before you see a provider.

Above all, speak to a doctor about any serious or life-threatening concerns. Prompt medical evaluation ensures you receive the right tests and care.