Free Hemoglobin in Serum (Mass Concentration)
This test measures the amount of free hemoglobin (the protein carrying oxygen in your blood) that is not bound to other substances in your serum.
["Assesses free hemoglobin levels for potential red blood cell breakdown or hemoglobin-related conditions."]
Key facts at a glance
- LOINC
- 4635-9
- Short code
- Hgb Free Ser-mCnc
- Synonyms
- Hgb Free Ser-mCnc
- Category
- hematology
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 12
- Ref high
- 17.5
- Critical range
- 7 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85018
- SNOMED
- 900000000000003004
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test to investigate conditions like hemolysis (destruction of red blood cells), certain blood disorders, or to monitor treatments affecting hemoglobin levels.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample, typically drawn from a vein in your arm. If you’re on blood-thinning medication, let your provider know.
What the Results Mean
Elevated levels may suggest red blood cell destruction or hemoglobin leakage from damaged cells. Lower levels could indicate conditions affecting hemoglobin production or binding.
Common Conditions Monitored
This test helps diagnose or monitor hemolytic anemia, hemoglobinopathies (like sickle cell disease), or conditions where red blood cells break down prematurely.
Reference range
Adult males: 13.5-17.5 g/dL; Females: 12.0-16.0 g/dLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical significance: Free hemoglobin is a marker for intravascular hemolysis (destruction of red blood cells within the bloodstream). Elevated levels can indicate underlying conditions such as autoimmune hemolytic anemia, transfusion reactions, or certain infections. It’s also used in research or specialized clinical scenarios where precise hemoglobin measurement is critical.
Short name
Free Hemoglobin
Frequently asked questions
What causes free hemoglobin to be elevated?
How is this test different from a regular hemoglobin test?
Can lifestyle changes affect this test?
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