Chemicals in an outdated test may no longer work properly, so the results may not be valid. Don't use a previously purchased test with an expired date. Don't leave it in the car if you go elsewhere. No test is 100 percent accurate. Review the instructions and pictures until you fully understand each step.
Sequence is important.
Don't skip a step. If a step to check the test or calibrate an instrument is included, do it. Use a stopwatch or a watch that counts seconds. If the test depends on color for a step, and you're colorblind, be sure someone who sees color interprets the results. If you have questions about the test results or their implications for your health, consult your doctor or other qualified health professional.