Ovulation Test: What is the Right Time to Take One?
Medically reviewed by Rachel Liberto, RN on August 6, 2019
Are you using an ovulation test to track ovulation and maximize your chances of getting pregnant? Before you go through the effort, it’s important to make sure you’re using it correctly.
An ovulation test (also sometimes called an OPK, which stands for ovulation predictor kit) is a test that detects the presence and concentration of luteinizing hormone (LH) in your urine.
Between 12 – 48 hours on average before ovulation, there is a brief surge in LH levels. The LH surge sends a message to your ovaries that it’s time to release an egg. When you get a positive ovulation test, it means that ovulation is likely imminent.
How many days will you get a positive ovulation test?
Some women may get positive ovulation tests for only a few hours, and others may get positive tests for many days in a row. But the important thing is when you got your first positive ovulation test, for it’s the beginning of the LH surge that determines when you ovulate.
The exact length of time between the beginning of the LH surge and ovulation varies from woman to woman. If you have a long LH surge, you can ovulate and still continue getting positive ovulation tests for several days after.
How soon after a positive ovulation test will I ovulate?
Most women ovulate 24 hours after the first positive LH test. However, there is substantial variability between and within women. Ovulation can occur while you are still getting positive ovulation tests.
Since the surge can sometimes last for a day or two, testing every day—or even twice a day, once in the morning and once in the afternoon—can help provide context for where in your surge you are.
Should I wait for a positive ovulation test to have sex?
No! You are most fertile during the 2 – 3 days before ovulation. This means that for many women, the most fertile days occur before the ovulation test even turns positive. If you always wait for an ovulation test to have sex, you could be missing some of your best days for getting pregnant on your personal fertility calendar.
If you know how to track your vaginal discharge—also known as your cervical mucus—you can usually get earlier warning of ovulation than ovulation tests will give you.
What is the best time of day to take an ovulation test?
Some tests require testing with your first morning urine, and other tests require testing with afternoon urine. It’s best to follow the instructions on the brand of test that you’re using.
The LH surge usually occurs in the morning, but it can take several hours for the hormone to appear in urine. This is why many brands of ovulation tests ask you to test in the afternoon.
Another factor to consider is the length of your LH surge. Some women have an LH surge that lasts for a few days, and other women have a surge that lasts only a few hours. Both are fine, but the latter is harder to detect if you’re only testing once a day in the morning. Many women find that they can only get a positive ovulation test when they test twice per day, once in the morning and once again in the afternoon.
What’s the right way to take an ovulation test?
- Follow the instructions on the package—different brands of tests have different instructions.
- Don’t drink excessive fluids before testing.
- Try not to urinate for at least four hours before testing.
When in my cycle should I start testing?
That depends on which type of test you’re using. Certain kinds of digital LH tests work by measuring changes in hormone levels from your personal baseline. In order to use these digital tests properly, you need to start testing before your LH surge begins. Follow the directions on the package insert to determine what day of your cycle, depending on your average cycle length, to start testing.
Don’t be tempted to use fewer testing sticks by starting your testing later in your cycle. If you miss the non-fertile days of testing, you will not be able to accurately identify the fertile days. For this reason, it’s also important to use one and only one test base per cycle.
The less expensive tests, like Wondfos, tend to work by looking for an absolute threshold of LH in your urine. This means that it’s not as important to start testing early. You want to test early enough that you won’t miss your LH surge, of course, but since the test isn’t establishing any kind of baseline, testing before the surge is not strictly necessary.
How do I use ovulation tests with an irregular cycle?
The best thing to do is decide when to start testing based on the length of your shortest cycle in the past six months. Then, continue testing until you detect a surge. If your cycle varies by a week or so, you can expect to go through up to 10 tests. The more your cycle varies, the more tests you’ll go through.
How can you tell if you are ovulating?
Getting a positive ovulation test does not necessary mean that you are ovulating. An ovulation test detects signs that your body is preparing to ovulate, but that doesn’t mean you will definitely go on to ovulate.
Some women’s bodies gear up to ovulate several times in the same cycle, but lose steam before the egg is actually released. If you have PCOS, hypothalamic amenorrhea, or just an irregular cycle, this might be happening to you. If this is the case, it’s particularly important to be aware of the fact that a positive OPK does not mean that you will ovulate. BBT charting can help confirm when ovulation actually happened, but only retrospectively. You’ll need to do it consistently for the entire month in order to get results, and even then it might not work.
Why do I never get a positive ovulation test?
There are a few possible explanations for why you might not be getting a positive result:
- You have a short LH surge. If your LH surge is on the short side, it’s possible to miss it if you’re only testing once a day. Try testing twice per day for one cycle.
- You have a very long cycle. If your cycle is on the longer side, you might have started testing too early.
- You didn’t ovulate. The most obvious reason for not getting a positive OPK is that you didn’t ovulate. This can be due to a variety of factors, such as stress, illness, or hormonal conditions.
- Malfunctioning tests. If you’re using the inexpensive online tests like Wondfos, you need to be careful about counterfeit tests. Wondfo OPK packages should be blue, with the word “Wondfo” in the drop logo. The testing strips should have a blue handle with the letters “LH” in darker blue.
Can you use an ovulation test to detect pregnancy?
It’s possible, but not advisable. The molecular structure of LH is similar to the molecular structure of hCG, which means that LH tests cannot distinguish between LH and hCG in your urine. So, if you’ve missed your period and have a positive LH test, then it’s possible that you’re pregnant, but it would be best to confirm with a pregnancy test specifically designed to measure hCG.
Hormonal mechanisms and the optimal use of luteinizing hormone tests in human menstrual cycle research James R. Roney, Hormones and Behavior Volume 106, November 2018, Pages A7-A9
Timing is crucial: Some critical thoughts on using LH tests to determine women's current fertility Janek S.Lobmaier, Laura M.Bachofner, Hormones and Behavior Volume 106, November 2018, Pages A2-A3