How accurate is a pregnacny test when on birth control (iud)?

Same as without IUD: A pregnancy test, when done correctly, at the right time, has about the same accuracy regardless of whether or not a woman is on a birth control method or not (such as an iud or birth control pills). Technically speaking, a positive pregnancy test may be more likely to be a false positive if a woman is on birth control, because the birth control makes it less likely for her to be truly pregnant.