Rexall pregnancy tests are generally accurate when used correctly. Like virtually all home pregnancy tests sold in the United States, Rexall tests detect the hormone hCG in urine and claim over 99% accuracy when taken on or after the day of your missed period. That number holds up well in practice, but real-world accuracy depends heavily on timing and how closely you follow the instructions.
How Rexall Tests Work
Rexall pregnancy tests use the same basic technology as name-brand tests like First Response or Clearblue. A chemical strip reacts with hCG, the hormone your body starts producing after a fertilized egg implants in the uterus. If hCG is present above a certain threshold, a colored line appears in the test window alongside the control line.
The sensitivity of a test refers to the lowest concentration of hCG it can detect. Most drugstore tests, including Rexall, pick up hCG levels around 20 to 25 mIU/mL. Your hCG levels roughly double every two to three days in early pregnancy, so testing just a day or two earlier than recommended can mean the difference between a clear positive and an ambiguous result.
When Timing Affects Accuracy
The biggest factor in whether your Rexall test gives you a reliable answer is when you take it. Testing on the first day of a missed period or later gives you the best shot at an accurate result. Testing before your missed period is possible, but hCG may not have built up enough to trigger a visible line, leading to a false negative.
Time of day matters too. First-morning urine is more concentrated, which means it contains higher levels of hCG per volume. If you test later in the day after drinking a lot of fluids, you’re essentially diluting the hormone and making it harder for the test to detect. This is especially relevant in very early pregnancy when hCG levels are still low.
False Positives and What Causes Them
False positives on home pregnancy tests are uncommon, but they do happen. The most frequent cause is a chemical pregnancy, where an egg was fertilized and briefly began producing hCG but never implanted in the uterus. The test correctly detected hCG, so it wasn’t technically wrong, but the pregnancy doesn’t continue. Chemical pregnancies are surprisingly common and often go unnoticed without a test.
A recent miscarriage or delivery can also produce a positive result because hCG can remain in your blood and urine for up to six weeks after a pregnancy ends. Fertility treatments involving hCG injections are another well-known cause. If you’re undergoing treatment to stimulate ovulation, testing too soon after an injection will pick up the medication rather than a new pregnancy.
Several medications can also interfere with results. Antihistamines, antianxiety medications, antipsychotics, diuretics, certain Parkinson’s disease medications, and methadone have all been associated with false positives. If you’re taking any of these and get an unexpected positive, a follow-up blood test from your doctor will give you a definitive answer.
Expired or improperly stored tests are another culprit. The chemical reagent that reacts with hCG degrades over time, and a test that’s been sitting in a hot car or past its expiration date may not work as intended. Always check the date on the box before using it.
False Negatives Are More Common
You’re more likely to get a false negative than a false positive. The usual reason is testing too early, before hCG has reached detectable levels. If you get a negative result but your period still hasn’t arrived after a few days, test again. By that point, hCG levels will have risen significantly if you are pregnant.
Drinking large amounts of water before testing can dilute your urine enough to push hCG below the detection threshold. Not holding the test strip in urine long enough, or not waiting the full development time before reading, can also produce a false negative. Each test has a specific protocol printed in the instructions, usually involving holding the strip in urine for a set number of seconds and then waiting three to five minutes to read the result.
How to Read Your Results Correctly
Read your Rexall test within the time window specified in the instructions, typically three to five minutes. After that window closes, the urine on the test strip begins to dry, and something called an evaporation line can appear. This is a faint, colorless streak that sits where the positive line would be. It looks like a watermark or a shadow, and it contains no visible dye.
The key distinction: a true positive line has color, even if it’s faint. In very early pregnancy, a positive line might be light pink or light blue depending on the test design, but it will clearly contain pigment. An evaporation line is colorless. If you see a mark that you can’t tell whether it has color, the safest approach is to retest with a new strip the following morning using your first urine of the day. A day’s worth of rising hCG will usually produce a more definitive result.
Never fish a test out of the trash hours later to re-examine it. Any line that appears well outside the reading window is unreliable.
Rexall vs. Name-Brand Tests
There is no meaningful accuracy difference between Rexall tests and more expensive brands. All home pregnancy tests sold in the U.S. must meet FDA standards for performance. The core technology is identical: an antibody on a strip binds to hCG and triggers a color reaction. What varies between brands is sensitivity (how early they can detect pregnancy), ease of use (digital readouts vs. line-based), and price.
Where Rexall and other store-brand tests genuinely shine is cost. If you want to test early and expect you might need to retest a few days later, buying an affordable option lets you do that without spending significantly more. Two tests a few days apart will give you more reliable information than one expensive test taken too early.