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Can an ovulation test be used as a pregnancy test?

Written by: Dr. Amy Beckley, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

Written on 1/27/21

What is an ovulation test?

An ovulation test is a hormone test strip that helps you track your cycle and predict when ovulation is going to occur, so that you can better time intercourse in case you want to get pregnant. Ovulation tests detect luteinizing hormone (LH) — the hormone that triggers ovulation — levels in your urine.

When during my cycle do I use an ovulation test?

During the first half of your cycle, also called the follicular phase, your follicles grow under the influence of follicle stimulating hormone (FSH) until a mature follicle takes the lead and prepares to ovulate. As your egg is maturing, it releases estrogen in order to thicken your uterine lining in preparation for implantation.

Once your estrogen reaches a certain level a signal is sent to your pituitary gland, telling it that the egg is ready to be released. An LH surge occurs next, triggering the follicle to release the mature egg in the next 24-36 hours — a.k.a. ovulation!

The purpose of ovulation tests is to predict when ovulation is going to occur by checking your LH levels throughout your follicular phase until a surge is detected on your peak fertility day. This is important as conception can only occur during the few days leading up to and day of ovulation.

For women with regular 28 days periods, ovulation usually takes place around cycle day 14. But hormones shift and fluctuate monthly, meaning you can’t just rely on a previous pattern when it comes to ovulation.

Can an ovulation test be used as a pregnancy test?

The purpose of ovulation tests is to predict when ovulation is going to occur by checking your LH levels throughout your follicular phase until a surge is detected on your peak fertility day.

How early should I start testing for ovulation?

If you want to have an accurate image of your follicular phase, you’ll need an ovulation test. Some medical professionals recommend that you start testing your LH levels as early as when your period ends, roughly around cycle day 6.

If you are using Proov LH Tests, we recommend beginning testing about 18 days before your next suspected period. This means that if your cycle is 28 days long, you’ll want to start using Proov LH Tests on cycle day 10.

You may want to keep in mind that an LH surge may only last for a couple of hours, meaning testing only once a day may cause you to miss that surge. As you near your surge, you may want to start testing twice a day, once in the morning and once in the evening to ensure you catch the LH surge.

An ovulation test is considered positive when both your control and your test lines are of the same color and intensity. You can then assume your LH is surging, your fertile window is open, and you can expect ovulation to take place in the next 36 hours.

However, it’s important to note that while your LH can surge and you’ll get a positive ovulation test, this doesn’t always mean you’ve ovulated. This is why it’s important to use PdG tests after ovulation to ensure an egg was released and it was successful.

Can an ovulation test be used as a pregnancy test?

If you are using Proov LH Tests, we recommend beginning testing about 18 days before your next suspected period.

What is a pregnancy test?

A pregnancy test is another hormone test that helps us detect human chorionic gonadotropin hormone (hCG) levels in urine from home. HCG is the hormone released by cells in the developing placenta after an embryo has implanted into the uterus.

When do I use a pregnancy test?

In order for a urine pregnancy test to be positive, the cells in your developing placenta need to start producing hCG. This happens as soon as the fertilized egg implants inside the uterus. Studies show that the most common implantation day is 9 days post ovulation, but an embryo may implant as early as day 6 or as late as day 12 after ovulation.

Since there is no way you can possibly know when exactly implantation is going to take place, most home pregnancy tests recommend you test the day of or the day before a missed period. Of course, if implantation happened earlier, your body will start producing hCG earlier, and you may get a positive pregnancy test as early as 7 or 8 days post ovulation.  However, this can be rare and false negatives are more common if you test too early.

Again, you should ideally test on the first day of your missed period, but we know that’s a long time to wait! Other studies show that you can test for pregnancy starting around 10 days post ovulation, with first morning undiluted urine, and still receive accurate results.

Can an ovulation test be used as a pregnancy test?

Other studies show that you can test for pregnancy starting around 10 days post ovulation, with first morning undiluted urine, and still receive accurate results.

So can an ovulation test be used as a pregnancy test?

Well technically you could, but it’s not recommended. Some women do use ovulation tests to check for pregnancy and it is true that when pregnant, your ovulation test may turn positive.

How does this happen, though, considering that ovulation tests detect LH and pregnancy tests detect hCG?

The secret is that both LH and hCG are glycoproteins, a type of protein molecule that has a carbohydrate attached to it. While they do perform different functions (LH triggers ovulation and hCG maintains pregnancy), they are still very similar in structure.

Due to this, some ovulation tests aren’t able to tell the difference between LH and hCG, meaning that if you use an ovulation test when pregnant, it may detect hCG and turn positive.

So while the science behind using an ovulation test as a pregnancy test is cool, for the sake of accuracy we recommend using each test for its intended purpose — i.e ovulation tests for predicting ovulation and pregnancy tests for confirming pregnancy. Additionally, some women may experience an LH surge right before their next period, meaning a positive ovulation test could give false hope of pregnancy. This is why we always recommend testing for pregnancy with a pregnancy test!

Luckily, we have many tools at our disposal to help us reach out fertility goals faster!