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What are the two types of COVID-19 diagnostic tests?

1. Antigen tests: available over-the-counter (also called ‘at-home tests’)

  • Most common type of rapid or point-of-care tests
  • Give rapid results and can be taken anywhere
  • Most often much faster
  • Most often cheaper than PCR (lab) tests
  • Tend to be less accurate when the result is negative
    • This means you may get a “false negative” result. For instance, your rapid test may show you are negative for an active COVID-19 infection. But a PCR test may show that you are actually positive. Sometimes testing more often can make up for some of these issues.

2. Molecular tests: PCR (polymerase chain reaction)

  • Done in a laboratory
  • Thought to be the most accurate testing option
  • Generally take longer. This is because tests must be sent to a lab, which often takes at least a few hours.

Antibody Test – What is it?

An antibody test (also known as a serology test) can detect antibodies to SARS-CoV-2 in your blood. Antibodies are proteins that your immune system makes to help fight infection and protect you from getting sick in the future.

Antibody tests should not be used to diagnose a current infection, but they may indicate if you had a past infection. Antibody tests help learn about how human immune systems defend against the virus, and about population-level protection. If you get an antibody test after receiving a vaccine, you might test positive by some (but not all) antibody tests. This depends on which type of antibody the specific test detects. 

Antibody testing is not currently recommended to determine:

  • If you have a current infection.
  • If you have immunity to SARS-CoV-2 following COVID-19 vaccination.
  • Whether you need to get a booster following COVID-19 vaccination.
  • Whether you need to quarantine after a known or suspected exposure to COVID-19.

Antibody testing is only covered by your Blue Shield plan if your healthcare provider orders it.

Who can get tested for COVID-19?

Everyone can get tested. Learn more about when and how Blue Shield covers tests.

When should I get tested?

If you have symptoms
Vaccinated or not, get tested immediately if you’re feeling any COVID-19 symptoms. If an antigen test is negative, take another test in 24-48 hours since they do not always detect early cases. 

If you were exposed
Anyone exposed to COVID-19 should consider getting tested as soon as possible, even if they do not have symptoms. 

Test again 5 days after exposure.

If you go to a high-risk event
Test before the event and 3-5 days after.

For mega-events of more than 1,000 people, it’s strongly recommended that attendees test 1 day (antigen test) or 2 days (PCR test) before the event.

If you travel
Test before the event and 3-5 days after.

Vaccinated or not, anyone entering or re-entering California should test 3-5 days after arrival.

What do I do if I test positive?

Speak with your healthcare provider about the next steps. Read more about getting care.

Getting tested

  • Order free at-home tests for your household at
  • At-home over-the-counter (OTC) tests can also be purchased online or in pharmacies and retail stores
  • OTC test kits that you buy on your own may be reimbursed by Blue Shield. Learn more about reimbursement through Blue Shield.

OTC test kits that you buy on your own may be reimbursed by Blue Shield. Learn more about reimbursement through Blue Shield.

If you need to obtain a test ordered by your healthcare provider, it is recommended you visit an in-network testing site.

In-network testing locations include these retail pharmacies:

Should I still get tested for COVID-19 even after I’ve been fully vaccinated?

Yes. If you have symptoms of COVID-19, you should get tested. This is true even after being vaccinated. Tests for COVID-19 work the same in vaccinated people as they do in unvaccinated people.