You should do a test if you miss your period or if you notice any changes in your body that could be signs of pregnancy. There are two different types of urine tests – one can be used from the first day of your missed period, and the other one (early test) can be done about 4 days before. However, the early test has a high error rate and is therefore not particularly accurate. Therefore, it may be better to do the pregnancy test from the first day of your missed period. Since the hormone hCG is highly concentrated from this day onwards, as opposed to the early test, it does not matter what time of day you take the pregnancy test.