About the Midstream Natalist Ovulation Test

How does this test work? It detects Luteinizing Hormone (LH) in your urine, which your brain makes to tell your ovaries it’s time to release an egg. LH levels surge about 24-48 hours before ovulation—conveniently when you’re most likely to get pregnant.

You’ll want to test for a few days in a row to get a sense for your cycle and find your LH surge timing. Some women have irregular cycles or ovulate on different days of their cycle each month. Everyone is different—this ovulation test will help you get to know your own body’s variations.

If you get a positive result and you’re trying to get pregnant this month, now is the time to get busy! Aim to have sex at least once in the next 48 hours leading up to ovulation. Knowing when you ovulate will help you plan ahead to maximize your chances of conception.

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What days to test

First, you’ll need to figure out how long your menstrual cycle is to know when to start testing. To do this, count the day your period starts (the first day of full menstrual flow) as Day 1, and continue counting until the day before your next period starts. The total number of days is your cycle length. For most women, this is around 28 days. If your cycle length varies each month by more than three days, choose the shortest cycle you’ve had in the last six months. Then, use the table to figure out which day of your cycle to start testing.

Ovulation usually happens mid-cycle, so if your cycle lasts 28 days, you’ll likely ovulate on Day 14. Your LH surge will start around 24-48 hours before ovulation—on Day 12 or 13.

Once you get a positive result, you can stop testing for that month. 

What time to test

You can test anytime of day, but make sure not to test after drinking a lot of fluid before it can dilute your urine. This is why many women prefer to test first thing in the morning when the urine is more concentrated.


  • Use before the expiration date on the wrapper

  • Don’t open the wrapper until you’re ready to start testing, and don’t use if the wrapper is damaged or torn

  • Store between 36-86°F (2-30°C) 

  • Don’t freeze this test

  • Keep out of children’s reach

  • Don’t use this test internally. For in vitro diagnostic use only. (In other words, if you put this test in your vagina, you’re doing it wrong.)

  • Not for contraceptive use

  • Use once

Taking the test

1. Unwrap one test and take the cap off to reveal the absorbent tip. Save the cap nearby—you’ll use it again soon.

2. With the test pointed downward, pee on the absorbent tip OR dip the test into a cup of urine for five seconds. Only get urine on the absorbent tip below the arrow. Pro tip: cover the testing window with your thumb as you pee.

3. Keep the test pointed downwards as you put the cap back on. Be careful not to let urine get above the arrow!

4. Lay the test on a flat surface with the result window facing up. Wait ten minutes to read your results.

Reading your results


The test window can display two lines:

  • The control line (C) to make sure the test worked.

  • The test line (T) that shows a positive result.

An important note about reading your results—unlike a pregnancy test, two lines alone is not a positive result since your body makes LH at low levels throughout your cycle. Make sure the test line (T) is as dark or darker than the control line (C) line for a positive result.

If the test line (T) is as dark or darker than the control line (C), the test is positive and you’ll likely ovulate within 24-48 hours. If you want to get pregnant this month, now is the time to have sex.

If only the control line (C) shows up or the control line is darker than the test line, the test is negative. Test again tomorrow.


When will my results show up and how long will they last?

Check your results after ten minutes—and make sure to read them within 20 minutes. After 20 minutes, the results won’t be accurate.

One line is darker than the other. What’s this mean?

That’s normal—it’s how these tests work. If the test line (T) is darker than the control line (C), your result is positive, and you’ll likely ovulate within 24-48 hours. If the test line (T) is lighter than the control line (C), your result is negative. 

It’s been ten minutes and the control line (C) never showed up. What’s going on?

It’s really rare, but either the test wasn’t saturated with enough urine—or it’s defective or expired (check the wrapper). Throw it out and try again with a new one. Send us a photo of the test (include the wrapper with its printed lot number and expiration date) to support@natalist.com, and we’ll help you out.

What can affect my results?

  • Certain conditions including a recent or current pregnancy (including a chemical pregnancy), menopause, or Polycystic Ovary Syndrome (PCOS).

  • Certain medicines such as birth control pills and fertility drugs. Ask your doctor for more info about your situation. 

  • Following instructions incorrectly.

  • Waiting too long to read your results. Results read after 20 minutes may not be accurate.

Note: If you’re taking medication like clomiphene citrate (e.g. Clomid*) or letrozole, ask your doctor about how and when to use these tests.

I recently stopped using “the pill” (hormonal contraception). Does it make sense to start testing now?

It may take a few months for your body to get back its pre-contraception cycles. If you’re interested in understanding your cycle during this time, this is a great way to help predict ovulation and time sex.

I’ve been using ovulation tests for several months, and I’m not pregnant. What should I do?

Don’t fret. It can take many months to become pregnant. A rule of thumb is if you haven’t conceived after six months of trying while you were tracking your ovulation, you should talk to your doctor.

I got a positive result but I don’t think I ovulated. What’s going on?

False positive results may occur in up to seven percent of cycles, especially for women with PCOS, primary ovarian insufficiency, or other medical conditions where LH may be elevated. If you think this could be you, talk to your doctor.

I’ve used all the tests and followed all the instructions, but haven’t detected an LH surge yet.

Some women don’t ovulate each cycle and so they wouldn’t see an LH surge in those months. Some women ovulate late in their cycle—so if you’re mid-cycle and haven’t detected a surge yet, keep testing each day until you do (and order more tests if you need them). It usually takes at least three to six months to figure out your own cycle patterns. If you’re concerned about your results, talk to your doctor. 

Will the amount of liquid I drink affect the results?

Yes. Don’t drink a bunch of liquid for a few hours before testing. It can dilute the urine and cause a false negative result—meaning you could be ovulating, but the test will show you’re not.

My cycle length is different each month. How do I know when to start testing? 

If your cycle length is different month to month by more than three days, choose the shortest cycle you’ve had in the last six months to figure out when to start testing. Another option is to start testing the day after the last day of your period in order to guarantee that you do not miss your LH surge.

What time of day should I test?

You can test anytime of day, but make sure not to test after drinking a lot of fluid because it can dilute your urine. This is why many women prefer to test first thing in the morning when the urine is more concentrated.

Do I need to use all the tests in this pack?

No. You can stop testing when you detect ovulation and save the remaining tests for your next cycle.

How accurate is the test?

The Natalist Ovulation Test is over 99% accurate in detecting LH based on a multi-center clinical evaluation of over 450 urine samples. 

When should I try to conceive based on my results?

Since sperm can live for up to five days after sex, it’s the five days leading up and the day of ovulation (six days total) that is considered your “fertile window.” Aim for sex every day or every other day during the fertile window. As you use these tests month to month and get to know your regular LH surge timing, you will be able to plan ahead to maximize your chances of conception during this time.

How sensitive is the test? 

The test can detect LH in urine at 25 mlU/mL.

Since this test tells me when I’m ovulating, can I use it as a contraceptive?

No. Sperm can survive for several days, so you can still get pregnant if you had sex before detecting your LH surge or after you think your fertile window may have ended. 

My test is expired. Should I still use it?


Can this test tell me how much LH is in my urine?

No, this test can’t measure how much LH is in your urine. It can only tell you if your LH levels are surging. 

What are the limits of this test?

Certain medical conditions and medications may affect the test’s ability to predict ovulation. These can include pregnancy, post-partum, menopause, breastfeeding, birth control pills, some fertility medications, and PCOS. Women with medically diagnosed fertility problems should ask their physicians if this product is suitable for them.

Have more questions?

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Download a PDF version of these instructions here.