Does Your COVID Test Line Darkness Show How Infected You Are? (2023)

The central theses

  • Rapid home antigen tests are widely available and can be a quick way to find out if you have COVID-19.
  • If you see a fast dark line on your COVID test, that's a pretty good indicator that you're positive.
  • While there are many factors that can cause a line on a COVID test to be faint or barely visible, it is safer to assume that any line on a test means that you are positive and that you should take precautions to avoid spreading the virus to others.

Does a strong dark line on a rapid COVID-19 test mean you are more contagious than a faint line?

According to experts, both the darkness of the line and the time it takes to appear can show how much of the COVID virus you have in your body and how likely you are to pass it on to others, but there are also some limitations you need to be aware of. of.

Here's what you need to know about how to interpret the lines on your COVID test and what to do if the line is faint.

What the lines mean on the COVID tests

When you open a home COVID test, you already see a line on it: that's the control line. When you do the test, see if another one comes up.

Do rapid home tests detect variants?

Andnew variants of the covid virusare emerging, there have been concerns that available home tests may miss them.

Most COVID home tests can detect Omicron variants such as BA.5 and BQ1. However, some people noted they had COVID symptoms before getting a positive rapid home test, so retesting could be key.

actually theThe Food and Drug Administration (FDA) recommends serial testingif you get negative results on a home test.

How this line appears depends on how many viruses are present, how you tested, whether the test has expired, and even the brand of COVID test you are using.

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Does the darkness of the line matter in a COVID test?

As researchers learned more about how rapid home tests work in the real world, they found that in many cases, the dark appearance of the line on the test corresponds to the amount of virus in a person's body.

"Viral load," in turn, is often related to how sick a person is and how likely they are to make other people sick.

Michael Mina, MD, PhD,Verywell, eMed's chief medical officer and a former professor of epidemiology at Harvard, said the darkness of a line on a positive rapid COVID test shows how much virus a person has in their body. The amount of virus in her body can also give you an idea of ​​how likely she is to pass the virus on to someone else.

“If your line is really dark, you could be a super spreader; You could go to a bar and infect 30 people,” Mina said. "If your line is very weak, especially late in the infection, you could infect your spouse with whom you sleep head to head on a pillow... but you're not likely to accidentally walk into a room infecting 30 people."

Can you still use a COVID-19 test at home if it is expired?

OthersExperts |Point out that differences between test marks and factors such as user error mean that you probably shouldn't rely on the obscurity of a test line to predict how sick a person will get or how many people they might spread the virus to.

For example, you could still get COVID even if the line on your test wasn't as dark, especially if you have risk factors like underlying health conditions.

Experts tend to agree that it's best to be cautious and proactive when you get a potentially positive COVID test.

A spokesperson for Abbott, the company that makes one of the most widely used rapid home COVID tests (BinaxNOW COVID-19 Antigen Self Test) - Verywell said the most important thing to know is that if that second line shows up on your test, even if it's faint, it's positive.

If you test positive, you should assume you have COVID and could spread it to others, even if you don't feel sick.

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What does it mean if you test positive quickly?

Mina said that a positive COVID test within seconds shows that you have a high viral load and a greater potential to spread the virus to others.

“If a line reaches its peak of darkness after 10 minutes, that means it has a lot of virus,” Mina said. “But if it reaches its peak of darkness after 20 seconds, that means you are ahugeLots of viruses."

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Are rapid tests better than PCR?

Rapid COVID antigen tests better detect infectivity in real timeals PCR-Tests, but both are used in specific situations.

"An antigen test is like a security guard," says Mina, explaining that rapid tests detect viral proteins. "A security guard works by recognizing that something bad is happening at that moment and can act immediately."

Mina said that a PCR test detects the genetic material of a virus and is more like a forensic detective who "shows up at the scene after the crime has already occurred."

Can rapid tests be wrong?

Both rapid and PCR tests can be wrong, but Mina said it was highly unlikely that a person would test positive on a rapid test unless they had COVID.

What to do if you get a weak line

If you see a fast, dark line, it's probably pretty clear that your COVID test is positive. However, Mina emphasizeda faint line that appears slowly on a testor even one that is a bit fuzzy or fuzzy can still mean you have high levels of the virus in your body.

"For a virus to collect enough molecules in these tests to be able to show a line, that means there's a lot of virus there," Mina said.

When you think you're at the beginning of COVID infection and sees a faint line on her test, Mina said she needs to be more careful as her viral load can increase in a matter of hours or days.

If you still see a faint line on the other side of the infection, even after your symptoms have improved or you have received treatment for COVID (eg.paxlovid), it's best to take this as a sign that you might still be contagious.

While that may not be the case, somePeople can still test positive even when they can no longer spread the virus, you really can't know.

What should you do if you feel sick but continue to test negative for COVID?

Amake things even more confusingIf you have already had COVID or been vaccinated/boosted, you could have a weak line at first and then test negative if your body can fight the virus quickly. However, it is important to note that unless you use a test to look for antibodies instead of active infection, the vaccination will not test positive.

Getting some clarity on a faint line is whereserial teststrying to "catch" peak viral loads may be helpful. If you get a negative or questionable positive on your first test, retesting in a day or two can give you a much clearer result.

Mina said that even if the lineage is almost non-existent, the safest bet is to assume you are still positive and take steps to prevent others from becoming infected.

That means masking up and trying to stay away from others (particularly those who may be at high risk) until you recover and test negative (which according to recent research is a relatively safe bet that you're no longer contagious).

"It's a good rule of thumb to assume that if you're positive, you're contagious," Mina said. "I also think it's reasonable to explain to people that if you previously had a very dark line, you have fewer infections and now your line has become very faint."

That said, even with a faint line on a positive test, Mina advised: "Don't visit Grandma."

what that means to you

If you see a line on your COVID test, play it safe and take precautions to avoid spreading the virus to others. While a rapidly appearing dark line is a sign that you have more virus in your body, even a faint line can be positive (and may darken as you retest in the next few days).

The information in this article is current as of the date shown, which means that more recent information may be available at the time you read this article. For the latest updates on COVID-19, please visit ourcoronavirus news page.

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