Immunoglobulin G (IgG) Antibody to SARS-CoV-2 (Nucleocapsid Protein) - Qualitative
This test detects antibodies in your blood that your immune system produces in response to the SARS-CoV-2 virus, which causes COVID-19. It helps determine if you had an infection at some point, even if you didn’t experience symptoms.
This test can indicate past exposure to COVID-19, not current infection status.
Key facts at a glance
- LOINC
- 97090-5
- Short code
- HOWOFTENLOCALGOVERNMENTOFFICIALSUSEDASSOURCEOFINFORMATIONFORCOVID19
- Synonyms
- —
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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
What This Test Measures
The test looks for IgG antibodies specific to the nucleocapsid protein of SARS-CoV-2. These antibodies are part of your immune response after your body has encountered the virus. While IgG antibodies can persist for months or years, they don’t always mean you’re immune to future infection.
How the Test Works
A small blood sample is taken from your arm. The sample is tested in a lab to detect the presence of IgG antibodies against the virus’s nucleocapsid protein using an immunoassay method. This helps identify if your immune system has recognized and responded to the virus.
When You Might Need This Test
This test may be recommended if you’ve had COVID-19 symptoms in the past, received a positive PCR or antigen test, or if you’re in a setting where monitoring past exposure is important (e.g., healthcare workers, travelers, or research studies). It’s not used to diagnose active COVID-19.
What to Expect Before the Test
No special preparation is needed. Wear comfortable clothing and bring a photo ID. You may feel slight discomfort from the needle, but it usually goes away quickly. If you’re pregnant, have a bleeding disorder, or take blood-thinning medications, let your provider know.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Positive results suggest past infection with SARS-CoV-2, meaning your body has developed antibodies to the virus. However, antibody levels can decline over time, and they don’t guarantee immunity. This test is useful for research, tracking exposure in populations, or assessing immune response in certain clinical settings. Negative results mean no detectable antibodies were found at the time of testing, but this doesn’t rule out past infection.
Short name
IgG Anti-Nucleocapsid COVID-19 Antibody Test
Frequently asked questions
How long do IgG antibodies last after COVID-19?
Can this test be used to confirm a past COVID-19 diagnosis?
Why might my antibody levels be low or absent?
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