Stool Fecal Occult Blood (Hemoglobin) Test, Immunochemical (Fecal Immunochemical Guaiac-Free)
This test detects hidden blood in your stool, which may signal conditions like bleeding from the digestive tract.
["Early detection of hidden blood can help identify potential gastrointestinal issues before symptoms appear."]
Key facts at a glance
- LOINC
- 34402-8
- Short code
- Copro/Hgb RBC
- Synonyms
- Copro/Hgb RBC
- Category
- hematology
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 7 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Doctors may recommend this test to check for signs of internal bleeding in the digestive system, such as ulcers, polyps, or cancer. It’s often used as a screening tool for colorectal cancer or to investigate symptoms like unexplained weight loss, abdominal pain, or changes in bowel habits.
How the Test Works
A small sample of stool is collected and tested for hidden blood using a sensitive chemical reaction. This method is more accurate than the traditional guaiac-based test and can detect even small amounts of blood.
Sample Collection
You’ll need to collect a stool sample at home using provided collection kits. Follow the instructions carefully to ensure accurate results. Bring the sample to your lab or clinic on the same day for testing.
What to Expect Before the Test
No special preparation is usually needed, but avoid using certain foods or supplements (like vitamin C or red meat) that could interfere with the test results for 3 days before collection.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test plays a crucial role in early detection of gastrointestinal bleeding, which could be caused by conditions like colorectal cancer, hemorrhoids, or peptic ulcers. Early identification can lead to timely medical intervention and better outcomes.
Short name
Fecal Occult Blood (FOB) Test
Frequently asked questions
What does a positive result mean?
Can I eat normally before taking this test?
How often is this test recommended?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy