Test first thing in the morning. Your urine is the most concentrated when you wake up. If you test later on in the day, avoid lots of fluids — too much water can dilute urine and impact the result.
You can test up to 6 days before your missed period — but your results will be the most accurate if you test on the first day of your missed period (that’s also what most doctors recommend). If you test before your missed period and get a negative result, you could still be pregnant. As the hCG in your body increases, the results become even more accurate.