A COVID-19 test result means nothing if you don't stay home and isolate for days before taking it

• You should self-isolate for 5 to 7 days before getting tested for COVID-19 and stay home until you get your results.
• That might require quarantining after a possible exposure or planning ahead before traveling.
• Testing too early, or seeing people while you wait to get tested, means your results won't catch your most recent exposures.
• Going out into the world before you get your results back could also invalidate a negative test.

If a coronavirus test provides a snapshot of your viral load at a given moment in time, isolating before and after getting tested ensures that you'll get the most focused, accurate portrait possible.

Experts have cautioned against using a negative test result as a "golden ticket" to gather with family or board a flight, but the US just established a policy that will require international travelers to show their testing receipts before flying into the country starting January 26. What the order lacks is any oversight of when and how people get tested, as well as how they behave in the interim between getting the swab and receiving their results.

Although some might feel compelled to get a COVID-19 test just a couple days before a flight or immediately after learning they came into contact with someone who is sick, it's best to wait five to seven days after any possible exposure before getting tested. During that waiting period and the time it takes to get your results back, it's essential to stay home and self-isolate - otherwise, you're back to square one.

Say you got tested for COVID-19 at your local urgent care clinic a week after hearing that a friend you met for dinner came down with the illness. During that week, you went grocery shopping and drove your kids to daycare. It may feel like you were doing as little as possible, but, in reality, you set off a chain of potential new exposures.

In the worst case scenario, you test positive and learn you've put your kids, their classmates, and your fellow shoppers at risk. A more complicated outcome is that you test negative, giving you a false sense of security while the coronavirus could still be silently incubating in your body.

If you stayed home and kept away from others during that week, you would have a greater degree of confidence in your test results. But without an isolation period, it's impossible to be sure you weren't exposed just before or after your test.

Even the best coronavirus tests have an approximate 5-day blind spot

Molecular tests, such as the RT-PCR, are capable of detecting at least seven out of every 10 COVID-19 infections, Insider reported in October 2020. But to achieve that level of accuracy, you have to give the virus time to replicate in your body so it will show up on a test.

It takes the coronavirus between two and 14 days to incubate, or four to five days on average, according to the Centers for Disease Control and Prevention. During that incubation period, you may be somewhat infectious even if you test negative.

"You become infectious some time between when you're infected and when you test positive, we don't know exactly when," Lisa Lee, Virginia Tech professor and public health expert who spent 14 years working at the CDC, previously told Insider's Hilary Brueck.

That's why it's so important to quarantine for at least 10 days after a potential exposure, or seven days with a negative test, according to the Centers for Disease Control and Prevention's most recent advisory. It's the only way to cover your bases and ensure you don't expose anyone else in the time it takes to get an accurate test result.

You should also stay home and self-isolate while you wait for your test results

If you go about your regular errands as you wait for your test results, you could not only expose others if it turns out you're positive, but also cancel out any peace of mind that comes with a negative result.

"You can be negative today, contract tomorrow, and be positive the day after," Anand Swaminathan told Insider's Susie Neilson.

To avoid invalidating your test results, you should self-quarantine while you wait to hear back. And if your household includes other people who go out in the world, they should either stay home or stay away from you.

"If your kids are going to school or playing sports or going to daycare, you're not quarantining," Swaminathan said.