You may have heard that ovulation tests can be used to test for pregnancy. In this guide, we’ll walk through the somewhat complicated answer.
This isn’t a straightforward answer, so let’s talk through some of the considerations and variables.
Can ovulation tests detect the pregnancy hormone, HCG?
The short answer is that ovulation tests can (sort of) act as a pregnancy test because LH is molecularly very similar to hCG. If you are pregnant, your hCG levels will be much higher than normal and an ovulation test may inaccurately detect this and read it as a high LH value. This is not to say that ovulation tests can substitute for a pregnancy test—pregnancy tests are much more accurate.
How ovulation tests work
An ovulation test is a test that lets you predict when you are going to ovulate. This is important because eggs only live for a short time after they are released—24 hours max. If you’re trying to get pregnant, you want to have sex before you ovulate to optimize your chances of getting pregnant. Sperm are relatively hearty and can survive for five to six days inside the female reproductive tract, so if you have sex before ovulation, they’ll stick around waiting for their moment to act.
There are many different types of ovulation tests, but they work by the same basic mechanism: by detecting Luteinizing Hormone (LH) in your urine. Your brain makes LH to tell your ovaries it’s time to release an egg. LH levels surge about 12-24 hours before ovulation—conveniently when you're most likely to get pregnant.
How do the hormones LH and hCG differ?
Both hCG and LH bind and function through a common hCG/LH receptor. The biggest difference between the two is that hCG has a circulating half-life that is approximately 80-fold longer than that of LH. One study refers to hCG as a “super LH produced in pregnancy,” with 80 times the biological activity of LH.
Because the protein components of hCG and LH look very similar, an ovulation test is unable to distinguish between LH and hCG in your urine. Therefore, the right amount of either hormone in your urine will result in a positive OPK result.
What does an ovulation test look like if you're pregnant?
An ovulation test isn’t as sensitive as a pregnancy test, so it won’t pick up hCG as early as a pregnancy test will, and it requires higher levels of hCG to turn positive. In addition, there is no way to distinguish whether the test is detecting your LH or HCG levels.
Can I use ovulation tests to test for pregnancy?
We do not recommend using ovulation tests to determine if you’re pregnant, for several reasons:
- Ovulation tests are not as sensitive as pregnancy tests (25 mIU/mL vs 10 mIU/mL).
- It’s nearly impossible to determine if a positive ovulation test is from LH or hCG.
Therefore, you run the risk of a false negative if it’s too early and a false positive if it’s picking up LH. If you think you might be pregnant, the best and most accurate way to confirm is to use an early detection pregnancy test.