A home pregnancy test works by detecting a hormone in urine called human chorionic gonadotropin (hCG). This pregnancy hormone is produced by the cells that make up the placenta. The amount of hCG increases quickly during early pregnancy. In many pregnancies hCG will double every few days and peak at about eight to twelve weeks.
hCG levels can be detected in urine approximately 12-14 days after conception. A blood test may detect hCG levels sooner at approximately 11 days after conception. Medications (prescription and over-the-counter) should not interfere with a pregnancy test result. The exception would be medications containing synthetic hCG that are sometimes used in fertility treatments.
If you’re sexually active and you have missed your period it’s wise to take a pregnancy test as soon as possible. You can buy one at your local pharmacy. Tests vary so make sure you read the directions very carefully including where it should be stored, when to take it and how to interpret test results. Also, hCG levels vary from woman to woman. Therefore the accuracy of a home pregnancy test might, too depending on when you take it.
If your test comes back positive, please call your doctor’s office. The receptionist may ask you for the first day of your last period and will tell you when to come in for your first prenatal visit. At that appointment you may have another test to measure how much hCG is present in your blood.
If your home pregnancy test comes back negative, wait a few days and take another one. If the test is still negative and you still haven’t had your period call your health care provider for advice.