Skip to content

Serum IgG Substance Concentration (Qualitative)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood, often checked to assess immune function or detect past infections.

Quick summary

["IgG helps fight infections and supports long-term immunity; low levels may indicate immune deficiency or chronic illness."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
5368-6
Short code
S pneum IgG Ser IA-aCnc
Synonyms
S pneum IgG Ser IA-aCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
CPT
82784
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 This Test Might Be Ordered

Your doctor may recommend this test if you have symptoms like frequent infections, unexplained fatigue, or if you’re being evaluated for conditions like HIV, lupus, or autoimmune diseases. It can also help monitor immune responses after vaccines or treatments.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from your arm. If you’re on blood thinners, let your doctor know beforehand to avoid unusual bleeding.

What the Results Mean

Results are qualitative (yes/no) rather than numeric. A positive result means IgG antibodies are present, confirming exposure to certain pathogens or immune activity. A negative result suggests no detectable IgG for that specific antigen.

Common Conditions Monitored

IgG testing is often used to diagnose or track conditions like chronic infections (e.g., tuberculosis), autoimmune disorders (e.g., rheumatoid arthritis), or immune system evaluations post-transplant.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG Antibodies Play a Critical Role

Short name

IgG Antibody Level (Qualitative)

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Follow-up with your doctor if you have questions about your specific test results.
Can I eat or drink before this test?
You can eat and drink normally before this test, as it’s a simple blood draw with no dietary restrictions.
What if my IgG levels are low?
Low IgG levels may signal an immune deficiency or chronic illness. Your doctor will discuss next steps, which could include further testing, lifestyle adjustments, or treatments to support your immune system.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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