causes of false positive urine pregnancy test
Blood or protein in the urine may cause false-positive pregnancy results. Urine hCG tests may give a false-negative result if the urine is too diluted or if testing is done too soon in the pregnancy. Certain drugs such as diuretics and promethazine (an antihistamine) may cause false-negative urine results.
Given the fact that any pregnancy test displays its results based on accurate measurement of the Human Chorionic Gonadotropin (hCG) hormone level, undergoing treatment with HCG injections causes a false rise in the hCG found in the urine and thus a false positive result.