Taking a rapid COVID test correctly comes down to a few key steps: checking the kit, swabbing properly, and timing the result. Most home tests follow the same general process, but small details in technique can make the difference between an accurate result and a misleading one. Here’s how to get it right.
Check Your Kit Before You Start
Before opening anything, look at the expiration date printed on the box. Many COVID test kits have received shelf-life extensions from the FDA, meaning your kit may still be valid even if the printed date has passed. You can look up your specific test on the FDA’s website, which maintains a searchable table by manufacturer and test name showing whether the expiration has been extended. If your kit is truly expired, the chemicals in the test strip may have degraded enough to give unreliable results.
If the kit has been stored somewhere cold, like a car trunk or garage, let it sit at room temperature for about 30 minutes before using it. The test components are designed to work within a specific temperature range, and cold reagents can slow the chemical reaction that produces your result. Lay out everything included in the kit: the swab, the test strip or cassette, the buffer solution (a small vial of liquid), and sometimes a small tube or tray. Read through the instructions for your specific brand before you begin, since details like buffer drops and wait times vary.
How to Swab Correctly
This is the step most people rush through, and it’s the one that matters most for accuracy. Home rapid tests use an anterior nasal swab, meaning you’re sampling just inside the front of your nose, not deep into your sinuses.
Insert the soft tip of the swab about half to three-quarters of an inch (1 to 1.5 cm) into one nostril. That’s roughly the full length of the cotton or foam tip. Press the swab firmly against the inside wall of your nostril and rotate it in a circular motion at least four times. Spend about 15 seconds per nostril. Then, using the same swab, repeat in your other nostril with the same technique. Using the same swab for both nostrils is intentional: it increases the amount of viral material collected.
A common mistake is barely grazing the inside of the nose or swabbing too quickly. The swab needs firm contact with the nasal wall to pick up enough material. It shouldn’t be painful, but you should feel gentle pressure. If it tickles or makes your eyes water slightly, you’re probably doing it right.
Processing the Sample
After swabbing, place the swab into the small tube of buffer solution that came with your kit. Most tests ask you to swirl or rotate the swab in the liquid for a set number of seconds, typically 15 to 30, then squeeze the tube against the swab as you pull it out. This step transfers the collected material from the swab into the solution.
Next, apply the specified number of drops from the tube onto the sample well on the test strip or cassette. The exact number of drops matters. Too few and the liquid may not travel across the test strip properly. Too many and you can flood the strip and get an unclear result. Follow your kit’s instructions on this precisely.
Timing Your Result
Most rapid tests require 15 minutes before you read the result, though some brands specify 10 or 20 minutes. Set a timer. Reading too early can show a false negative because the chemical reaction hasn’t finished. Reading too late, past the window stated in the instructions (usually 30 minutes), can produce misleading lines as the reagents continue to react on the strip. A line that appears well after the reading window does not count as a positive result.
How to Read the Lines
Every rapid test has a control line (usually marked “C”) and a test line (usually marked “T”). The control line must appear for the test to be valid. If it doesn’t show up, the test failed, regardless of what the test line shows. Discard it and try again with a new kit.
If both the control line and the test line appear, the result is positive. This is true even if the test line is extremely faint. A faint line still means COVID-19 viral particles were detected. As infectious disease specialist Thomas Russo at the University at Buffalo explains, a lighter line simply means less viral material is present, which could reflect early or late-stage infection. You should treat any visible test line, no matter how faint, as a positive result.
If only the control line appears and the test line area is blank, the result is negative. But a single negative result isn’t as reliable as a positive one, which is where repeat testing comes in.
What to Do After a Negative Result
A single negative rapid test doesn’t rule out COVID, especially in the first day or two of symptoms when viral levels may still be building. The FDA recommends repeat testing (called serial testing) for anyone who gets a negative result.
If you have symptoms, test again at least 48 hours after your first negative test, for a minimum of two tests total. If you don’t have symptoms but were exposed or simply want to confirm, test three times over five days, spacing each test at least 48 hours apart. This schedule gives the virus time to reach detectable levels if you are infected. One negative test on day one of a sore throat is far less meaningful than two negative tests spread 48 hours apart.
Common Mistakes That Affect Accuracy
Beyond swabbing technique, a few other errors can compromise your result:
- Blowing your nose right before testing. This can clear out the viral material you’re trying to collect. Avoid blowing your nose for at least 15 minutes beforehand.
- Eating, drinking, or brushing teeth shortly before testing. Some test instructions note this can interfere with results, particularly if a throat component is involved.
- Using too much or too little buffer solution. Apply exactly the number of drops specified. Squeezing the entire tube onto the strip is a common error with some kit designs.
- Reading results outside the time window. Lines that appear after 30 minutes can be evaporation artifacts, not true positives.
Throat Swabbing: Should You Do It?
You may have heard that swabbing the throat along with the nose improves accuracy. The UK’s National Health Service has recommended combined throat-and-nose swabbing for some of its rapid tests, and some people adopted this practice during the Omicron wave when early infection seemed to concentrate in the throat before the nose. However, virtually all rapid antigen test manufacturers in the U.S. still authorize only nasal swabs. The tests were designed and validated for nasal samples, so using a throat swab with a kit not designed for it could introduce inaccurate results. If your kit’s instructions say nasal only, stick with nasal only.
How Well Rapid Tests Detect Current Variants
Rapid antigen tests remain effective at detecting COVID, though sensitivity varies somewhat by variant. Research comparing test performance across variants found that most commercially available rapid tests detected Omicron and Delta at similar rates when measured by the actual amount of viral protein present. The apparent drop in sensitivity with Omicron that some studies reported was largely explained by the fact that Omicron samples contained less detectable protein per unit of viral genetic material, not because the tests themselves failed. In practical terms, rapid tests are most reliable when viral loads are high, which generally corresponds to the period when you’re most contagious. They are less likely to catch very early infections before the virus has replicated significantly, which is exactly why serial testing matters.