Q: I had an hCG human chorionic gonadotropin shot or injection to help me with ovulation. What will happen to the pregnancy test after my hCG injection?

A: Human chorionic gonadotropin (hCG) is a hormone produced by the placenta, but it is also made in a laboratory and given as an injection to help with certain fertility problems. A urine pregnancy test (HPT) tries to detect if the urine has hCG or not. If you have been given an hCG injection (Profasi, Pregnyl) to trigger ovulation or to lengthen the luteal phase of your cycle, trace hCG amounts can remain in your system as long as 10-14 (sometimes even more) days after your last injection. These hCG hormones from the injection can give you what's called a "false positive pregnancy test", a pregnancy test that is positive without actually being pregnant.

If you use a home pregnancy test after an hCG injection, wait 20 days before interpreting the test as positive or negative. The best way to detect a pregnancy after an hCG injection or shot is the hCG beta blood test. The blood test is much more sensitive than a urine pregnancy test. The blood hCG test can detect a pregnancy as early as 10 days after fertilization with one caveat. You need two tests several days apart. If you are not pregnant, then the blood hCG numbers will be zero or they will decrease.  If you are pregnant then they will rise.

As a general rule, in a normal pregnancy hCG beta numbers should go up by at least 60% in 2 days. If your blood hCG levels increase by at least 60% on the second day, then you are likely pregnant.

Read More:
Why Am I Not Ovulating?
When Am I Most Fertile?
Pregnancy Symptoms: Early Signs You May Be Pregnant