Quick highlights
- Key complement regulatory protein measured in angioedema evaluation
- Used when swelling occurs without hives and clinician suspects C1-INH-related pathways
- Often paired with C4 and C1-INH functional activity
- No fasting; simple serum blood test
- Specialist interpretation (allergy/immunology) is recommended
- Certain medicines (ACE inhibitors) can be clinically relevant—disclose use
- Not diagnostic alone; requires clinical correlation and sometimes repeat testing
- Home blood collection available in many service areas
- Clear safety guidance for airway swelling emergencies
- SEO coverage: C1 esterase inhibitor test, hereditary angioedema blood test, C1-INH level
What’s included
Preparation
- Book blood draw (home or lab)
- No fasting required
- Write down swelling history: location, triggers, frequency, presence/absence of hives
- Disclose medicines (ACE inhibitors, hormone therapy) to clinician
- Collect serum blood sample via trained phlebotomist
- If ordered, test C4 and C1-INH function for complete evaluation
- Download report from <a href='/my-account/'>View reports</a>
- Review with specialist; seek emergency care for breathing difficulty
FAQs
A complement regulatory protein; abnormal levels/function can be associated with certain angioedema patterns.
No.
No. It is supportive and typically interpreted with C4 and C1-INH functional testing.
C4 can be low in some C1-INH-related angioedema patterns and provides supportive context.
Levels and function may vary; clinicians interpret with clinical pattern and may repeat testing.
Yes. Some medicines (e.g., ACE inhibitors) can be relevant to swelling patterns; disclose all medications.
Often same day or within 24 hours depending on workflow.
Serum blood sample.
Yes in many serviceable areas.
Seek urgent medical care immediately, especially if breathing or swallowing is affected.
Yes, acquired forms are evaluated under specialist care; tests are interpreted in context.
Download from <a href='/my-account/'>View reports</a>.
Allergy/immunology or relevant specialist depending on clinical scenario.
No. Follow clinician advice for management and emergency plans.
Notes
Rare disorder evaluation requires specialist interpretation.
