Are you using urine-based ovulation tests to determine when you ovulate? Before you go through all that effort, it’s important to make sure you’re using them correctly. Here are answers to the most common questions about ovulation tests. 

What is an OPK?

An OPK (ovulation predictor kit) is a test that detects luteinizing hormone (LH) in your urine. Just before ovulation, you experience a brief surge in LH. This causes your ovary to produce enzymes which in turn cause a follicle to rupture and release an ovum: ovulation! By testing your urine every day at around the same time, it’s possible to pick up the LH surge. 

How soon after a positive OPK will I ovulate?

Usually, you’ll get a positive OPK the day before you ovulate, but it can also happen on the day of ovulation. Since you’re not going around testing your urine every hour, it’s hard to know the precise moment when your LH surge occurs. Most women ovulate between 12 – 48 hours after the LH surge. The important thing to remember is that if you get a positive OPK, it’s time to find your husband and get busy!

What time of day should I test?

The best time to test is around 2pm, but any time between noon and 8pm will do, as long as you are consistent.

Most women experience an LH surge in the morning, but it can take several hours for the hormone to appear in urine. This is why testing on first morning urine is not recommended. If you always test using first morning urine, you may miss your LH surge entirely. On the day of your LH surge, LH levels in your morning urine may still be too low for the test to pick up. And the surge may be over by the time you test the next morning.  

What’s the right way to take a test? 

  1. Take it at the same time each day—preferably in the afternoon.
  2. Don’t drink excessive fluids before testing.
  3. 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. Clearblue OPKs work by measuring changes in hormone levels from your personal baseline. In order to do this, you need to start using Clearblue tests 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 amount 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. 

The downside of tests like Wondfos is that if you have naturally lower hormone levels, it’s possible that your LH surge could be too low for the test to detect. 

I have a long/irregular cycle. How do I know when to start testing?

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. 

Does a positive OPK mean you ovulated?

Not necessarily. An OPK 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

[link], 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. Temping [link] 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.

I keep testing and never seem to get a positive result. Why?

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. Particularly if you’re using the online cheapies 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. 

 

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