Human Chorionic Gonadotropin (hCG) is one of the hormones most commonly associated with pregnancy. It is the hormone that pregnancy tests test for. Some tests are more sensitive than others are, although not all tests show the minimum hCG level measured on the box when you purchase it. The lowest level of hCG that a pregnancy test will measure is 25 mIU/mL. As pregnancy goes on, the hCG levels increase, doubling every 48-72 hours. Thus, the further along a woman’s pregnancy is, the more likely her hCG levels will register on a pregnancy test. 

There is an old question about whether a person can get a “false negative” or a “false positive” on a pregnancy test. As above, a false negative certainly is possible if the hCG levels are too low to register on the pregnancy test. If a woman has not gotten her regular period and the pregnancy test registers as negative, the woman is encouraged to re-test in a few days. Because hCG levels are usually only associated with pregnancy (and to a lesser extent, a woman’s menstrual cycle), the conventional wisdom is that a false positive on a pregnancy test is nearly impossible.

Here is where the conventional wisdom fails: hCG is sometimes administered as an injection to help women with fertility challenges. It is said to trigger ovulation and to lengthen the luteal phase of her cycle so that she will have a higher chance of conceiving. Lack of ovulation is a common reason for a couple being unable to conceive, so it is seen as something that can be quite helpful in a couple’s fertility quest.

Unfortunately, if a woman has gotten an hCG shot, her blood and urine hCG levels will likely reflect the hCG that she’s had injected, rather than the hCG from her potential new pregnancy. So it is possible for a woman who is not pregnant to get a positive result on a pregnancy test if she’s recently had an hCG shot.

So if you have had the shot, how will you know if you are pregnant or not?

The first method is the old fashioned pioneer woman method: waiting to see if your period comes when it is supposed to. This is not satisfying at all, and will likely take all the patience you have, especially knowing that pregnancy tests are available, but won’t work for you.

If you need to find out sooner, you can do some math and figure it out. hCG has a half-life of 28 hours in your body, which means that your hCG levels should decrease by half every 28 hours. There are three injection amounts; 10 000 IU, 5000 IU, and 2500 IU. If you have had the 10 000 IU shot, you’ll need to wait for at least 14 days after the shot to take the pregnancy test; the 5000 IU test will have you waiting ten days, and a week’s wait for the 2500 IU shot.

Each person’s journey to fertility is different; for some women, that journey involves an hCG shot. It may be the therapy that works, but you will have to wait to find out.