I personally don’t have much experience with this, but if you’re having a period, the likelihood that you are pregnant is slim. If you haven’t missed your period (or are experiencing period-like symptoms), but are concerned you may be pregnant it’s a good idea to contact your health provider for a blood test, which is much more accurate than a home pregnancy test prior to a missed period.
I don’t think at-home pregnancy tests are ever 100% accurate. However, if you are having your period and got a positive result, you should definitely see your medical practitioner. It could be that you’re not reading the test correctly, or that you’re not really having a period. Either way, you want to find out for sure what’s going on.
A urine pregnancy test looks for a hormone called Human Chorionic Gonadotropin (HCG) that is found in the urine during pregnancy. Having your period during the test should not interfere with the accuracy of these results. Within about 2 weeks after conception, there is enough of this hormone to show up in the urine. Also, when conception occurs, this signals other hormone changes to happen to stop the period from happening, because the lining that is shed during the period helps nourish the baby that is growing the uterus. There are times when a period might happen during pregnancy, but it is not that common for someone to have a normal period during pregnancy. However, if you are having other symptoms that you are not sure about, make an appointment to see your healthcare provider to talk about your concerns.
This is not intended to be medical advice. Everybody is different so please make sure to consult your physician if you're having issues. Do not delay or refrain from seeking professional medical advice from your physician because of something you have read on this site.