Your simple guide to COVID-19 testing

Last updated: Apr 22, 2021
Discover the differences between the two types of diagnostic COVID-19 tests and learn which one may be best for you.
Test guide

These days, there are plenty of reasons to be tested for COVID-19. Maybe you have symptoms, or you came in close contact with someone who has the virus. Or perhaps you’re getting ready to travel, visit a nursing home, or have surgery. These are all fair concerns.

There are a few different tests available for diagnosing an active COVID-19 infection. Each comes with its own strengths and weaknesses. Before you head to a testing site or buy a home test kit, it helps to understand the basics of COVID-19 tests. Here’s a look at how the two most common ones compare.

Blue Shield and Blue Shield Promise plans cover most diagnostic tests for individuals at no out-of-pocket cost to you. This means you do not need to pay out-of-pocket costs (copay, coinsurance, or deductible) for tests provided or ordered by a healthcare provider. Learn more about COVID-19 testing, including costs and locations, through our member site.

1. Molecular Tests


These tests go by a few names, including polymerase chain reaction tests (PCR tests) and nucleic acid amplification tests (NAATs). They test for genetic material from SARS-CoV-2, the coronavirus that causes COVID-19.

Where to get it: A doctor’s office, mass testing site, urgent care center, or pharmacy.

What to expect: A swab is used to gather a mucus sample from the nose or throat. Or you might spit into a tube for a saliva sample. Then the sample is sent to a laboratory for testing.;

How accurate is it? Molecular tests are close to 100% accurate when performed correctly. They don’t usually need to be repeated to confirm the results.

How long does it take to get results? A few hours to a couple of days.

What your results mean: If the test result is positive, you’re infected with COVID-19. You should self-isolate for 10 days and call your healthcare provider to ask about other important steps. If the result is negative and you have no symptoms, you may still need to self-isolate for a few days to watch for symptoms if you think you may have been exposed to someone who is infected. After that, keep taking steps to avoid getting sick.

If your test is negative but you have COVID-19-like symptoms, see your healthcare provider. Remember: A negative result means only that you didn’t have COVID-19 at the time you were tested; the sample may have been taken too early or too late in your infection for a positive result.

2. Antigen Tests


These tests look for antigens, specific proteins such as the spike protein that are made by the COVID-19 virus.

Where to get it: A doctor’s office, urgent care center, pharmacy, school health clinic, or nursing home.

What to expect: The tester will do a nose or throat swab to gather a mucus sample, which is usually tested at the same location.

How accurate is it? Positive results tend to be very accurate. False negatives are more common with antigen tests than with molecular ones. These results say you don’t have the virus when you do. False negatives happen about 20% of the time, depending on the quality of the antigen test and the tester.

How long does it take to get results? Less than an hour, sometimes within 15 to 30 minutes.

What your results mean: A positive result means you’re infected with COVID-19. Self-isolate for 10 days and seek added care from your healthcare provider. Negative test results may need to be confirmed by a molecular test, especially if you have symptoms of COVID-19.

Diagnostic test variations to know about


There are some variations of both types of diagnostic tests. Here’s what you need to know about them:

  • Rapid tests: There are rapid versions of both molecular and antigen tests. They use a mucus sample from the nose or throat, and they can be done wherever the sample is collected. The good news: Results are available in minutes to hours rather than days. The downside: Rapid tests may not be as accurate as tests where the sample is sent to a lab.
  • At-home collection tests: There are a few at-home molecular and antigen tests available at pharmacies and retail stores. Some require a prescription. They all require you to collect your own nasal or saliva specimen. You may use a simple device to test the sample yourself; results are ready within 30 minutes. Or you may need to send the sample to a testing facility. The results become available in a few days. As with all tests, false negatives are possible.
  • Combination tests: These can test for COVID-19 and the flu at the same time, which can help clear up confusion. Combination tests can be either molecular or antigen type tests, and they have the same accuracy described above for COVID-19 tests alone.


What about antibody tests?


Antibody tests can help confirm if you’ve had COVID-19 in the past. These blood tests look for antibodies or proteins that your body made to fight the virus while you were sick. But they can’t tell you if you’re infected right now, so they shouldn’t be used to diagnose COVID-19. 

A positive antibody test doesn’t mean you’re protected from the virus. It's important to keep following the Centers for Disease Control and Prevention guidelines to protect yourself. Also, an antibody test can be negative if it has been too long since you were infected, because antibody levels drop over time.

Final thoughts about COVID-19 testing


COVID-19 tests can be a very helpful tool if used wisely. Keep the following in mind:

  • Get a diagnostic test if you have symptoms of COVID-19, if you have been referred to get tested by your healthcare provider, or if you came in close contact with someone who had COVID-19 and you aren’t fully vaccinated. Also, think about getting tested if you’re planning to travel, see loved ones, or go to a nursing home.
  • No COVID-19 test is 100% accurate. The results can be faulty for a few reasons. For example, the swab might not collect traces of the virus. Sometimes, the sample gets contaminated. Or it could be that the test was done too soon after you became infected.
  • Even if you test negative, don’t stop following CDC guidelines for preventing the spread of COVID-19. The CDC recommends getting vaccinated against COVID-19 as soon as you’re eligible. Also, wear a mask, stay six feet away from others, wash your hands often, and avoid crowds.
  • Blue Shield and Blue Shield Promise plans cover most diagnostic tests for individuals at no out-of-pocket cost to you. This means you do not need to pay out-of-pocket costs (copay, coinsurance, or deductible) for tests provided or ordered by a healthcare provider. Learn more about COVID-19 testing, including costs and locations, through our member site.


The information in this story is accurate as of press time and posting. Getting vaccinated is one of the best ways to limit the spread of the coronavirus. It’s also important to continue practicing social distancing (keeping at least 6 feet away from people outside your household) and washing your hands frequently. You should also be appropriately masked any time you’ll be in public. According to the CDC’s latest guidance, this means layering a disposable mask underneath a snug-fitting cloth mask or placing a mask fitter over your cloth mask to ensure a tight fit. Because the situation surrounding COVID-19 continues to evolve, we encourage readers to follow the news and recommendations for their own communities by using the resources from the CDC, WHO, their local public health department and our COVID-19 member site.


Ready to get vaccinated? Find a location and schedule an appointment.


CMC: H0148_21_80_C_IA_04212021
Medi-Cal: Medi_21_51_LS_IA_04212021
MAPD: Y0118_21_242A_C 04212021

Blue Shield of California complies with applicable state laws and federal civil rights laws, and does not discriminate on the basis of race, color, national origin, ancestry, religion, sex, marital status, gender, gender identity, sexual orientation, age, or disability. Blue Shield of California cumple con las leyes estatales y las leyes federales de derechos civiles vigentes, y no discrimina por motivos de raza, color, país de origen, ascendencia, religión, sexo, estado civil, género, identidad de género, orientación sexual, edad ni discapacidad. Blue Shield of California 遵循適用的州法律和聯邦公民權利法律,並且不以種族、膚色、原國籍、血統、宗教、性別、婚姻 狀況、性別認同、性取向、年齡或殘障為由而進行歧視。