If you are scheduled to have a prostate specific antigen (PSA) test, there are a few things you should avoid doing beforehand in order to ensure accurate results. First, don't take any over-the-counter medications or supplements that could affect your PSA levels. This includes saw palmetto, beta-sitosterol, and stinging nettle root extract. You should also avoid vigorous activity for at least 48 hours before the test, as this can temporarily elevate PSA levels. Lastly, don't have a digital rectal exam (DRE) within 24 hours of your PSA test, as this can also skew results. If you have any questions about what you should or shouldn't do before your PSA test, be sure to ask your doctor.