Human Chorionic Gonadotropin (hCG)

Things that may affect the results of your test include:

• Doing a urine test for human chorionic gonadotropin (hCG) very early in pregnancy (during the first week after implantation) or on a urine sample taken in the middle of the day. The test may not always show an early pregnancy.
• HCG results may remain high (positive) for up to four weeks after a miscarriage (spontaneous abortion) or therapeutic abortion.
• Getting an injection of hCG to treat infertility. This may cause test results to appear high for several days after the injection.
• Having blood in the urine sample or soap in the collecting container, which may change the hCG level.
• Using diuretics and promethazine (such as Prorex, Phenergan, or Anergan). These medicines can cause false low hCG levels in urine test results.
• Using heparin, a medicine to prevent blood from clotting (anticoagulant)
• Using some medicines. These include hypnotics (such as Ambien), antipsychotics, and antinausea medicines (such as prochlorperazine and promethazine ). Be sure to tell your doctor what medicines you take.