Most at-home COVID tests follow the same basic process: swab your nose, mix the swab in a liquid solution, apply drops to a test card, and wait about 15 minutes for results. The details matter, though. Small mistakes in timing, swab technique, or reading the result can mean the difference between an accurate answer and a misleading one.
Before You Start
Check the expiration date on the box before anything else. Many at-home tests have had their shelf lives extended by the FDA, so the date printed on your box may no longer be accurate. You can look up your specific test on the FDA’s website to see if the expiration has been pushed out. Several common brands now have shelf lives of 20 to 24 months from manufacture.
If you’re using a nasal swab test (the most common type), you don’t need to fast or avoid food beforehand. If you happen to have a saliva-based test, wait at least 20 minutes after eating or drinking before collecting your sample. Eating right before a saliva test can interfere with virus detection.
Wash your hands, lay out all the components on a clean surface, and read through the full instructions for your specific brand before you begin. While the general steps are similar across tests, details like the number of drops or wait time can vary.
When to Test for the Best Accuracy
Timing has a big effect on whether a rapid test catches an infection. If you have symptoms like a sore throat, congestion, or fever, test right away. Your viral load is typically high enough at that point for detection.
If you were exposed to someone with COVID but feel fine, wait at least 5 full days after the exposure before testing. The virus can take 2 to 5 days (sometimes longer) to build to detectable levels, so testing too early often produces a false negative.
Step-by-Step Swab and Test Process
Open the swab package without touching the soft tip. Gently insert the absorbent tip about half to three-quarters of an inch into one nostril. That’s not deep; you’re swabbing just inside the nose, not reaching toward your brain. Press the swab firmly against the inside wall of your nostril and rotate it in a circular motion at least 5 times. Then, using the same swab, repeat the process in your other nostril. Spend at least 15 seconds total collecting the sample, and make sure you pick up any nasal moisture on the swab.
Next, open the small tube of liquid (called buffer solution) that came in your kit. Insert the swab into the tube, push the tip to the bottom, and stir it at least 15 times. This mixes the collected material into the solution. Squeeze the sides of the tube against the swab as you pull it out to extract as much liquid as possible, then safely discard the swab.
Finally, use the tube’s dropper cap to apply the specified number of drops (typically 3) to the sample port on the test card. Set a timer, as most tests require 15 minutes before you read the result. Reading it too early or too late can give an inaccurate reading.
Reading Your Results
A control line (usually labeled “C”) should always appear. If it doesn’t, the test failed and you need to start over with a new kit. A second line near the “T” (test) mark means the result is positive.
A faint line counts as a positive result. This is one of the most common sources of confusion. Even a barely visible line means the test detected viral particles. As Johns Hopkins infectious disease expert Amesh Adalja has put it, “A faint line is a positive test result.” The line’s darkness roughly reflects how much virus is present. A faint line could mean you’re in the early stages of infection or that you’re on the tail end, but either way, you’re carrying the virus.
What a Negative Result Actually Means
A single negative result on a rapid antigen test is not definitive. These tests are less sensitive than the PCR tests used in clinical labs. In a CDC study comparing the two methods, rapid antigen tests detected only about 47% of infections that PCR caught. They’re much better at identifying people who are actively contagious (about 80% sensitivity when compared against viral culture), but they can miss infections in their earliest stages.
Because of this, the FDA recommends repeat testing after any negative result. If you have symptoms, test again 48 hours later for a total of at least two tests. If you don’t have symptoms but suspect exposure, test three times over five days, spacing each test 48 hours apart. A negative followed by a positive on the second or third test is a common pattern, especially early in an infection.
A Throat Swab May Improve Detection
Your test kit’s official instructions will direct you to swab your nose, and that’s the FDA-authorized method. However, research on recent Omicron variants suggests that combining a throat swab with a nasal swab improves detection rates. One study found that nose-only swabbing had 91% sensitivity while a combined throat-and-nose approach reached higher accuracy. Some people swab the back of their throat first (gently rubbing each tonsil a few times), then swab both nostrils with the same swab, before dipping it in the buffer solution. This isn’t in the official instructions, but it’s a widely discussed technique that many healthcare professionals have endorsed informally.
What to Do After a Positive Result
Current CDC guidance treats COVID similarly to other respiratory viruses. If you test positive, stay home and away from others while you’re sick. You can return to normal activities once your symptoms have been improving for at least 24 hours and any fever has been gone for a full day without fever-reducing medication.
For the 5 days after you resume normal activities, take extra precautions: wear a well-fitting mask around others, keep your distance when possible, and prioritize good ventilation in shared spaces. These steps help reduce the risk of passing the virus along during the tail end of your contagious window.
Rapid Antigen vs. PCR Tests
The tests you buy at the pharmacy are rapid antigen tests. They detect proteins on the surface of the virus and return results in about 15 minutes. PCR tests, typically administered at clinics or labs, detect the virus’s genetic material and are significantly more sensitive. PCR results usually take hours to a day or more.
Rapid tests are best for answering a practical question: am I contagious right now? Their strength is convenience and speed. PCR tests are better for confirming or ruling out an infection with higher certainty, which is why a doctor may order one if your rapid tests keep coming back negative but symptoms persist. For most everyday situations, a properly timed rapid antigen test (or a series of them) gives you a reliable answer.