How Do Ovulation Tests Work?
A few different kinds of ovulation predictor kits (known in short as OPKs) exist but they all do the same thing: measure the ovulation hormone in your body to tell you when you are going to ovulate so if you are trying to get pregnant, you can have sex at the most fertile time of your menstrual cycle.
The easiest ones to use in terms of evaluating the results are:
How do they Work?
Ovulation tests function in the same manner as pregnancy tests; you collect a sample of urine and dip a small stick inside. Ovulation tests detect luteinizing hormone (LH). Just prior to ovulation, women experience a brief surge in LH. Ovulation tests help you pinpoint this surge and anticipate ovulation - your most fertile period in your cycle. A surge in LH indicates that ovulation should occur within 24 to 48 hours
When Should I Begin Testing?
To determine when to start testing, you must first determine the length of your menstrual cycle. The length of the menstrual cycle is the number of days from the first day of menstrual bleeding to the day before bleeding begins on the next period. Determine the usual length of the menstrual cycle over the last few months. Testing should begin 12 days after the first day of your menstrual period and continue until an LH surge is detected. However, if your cycles are shorter than 28 days, you should begin testing a few days earlier than day 12.
If you don’t know how your menstrual cycle is but you get a period once a month, then you can start using ovulation tests from when your period ends until you get a positive. This can get expensive as you will need lots of tests so it is better to get to know when you ovulate. For more on how to do that, watch here.
Is it Important What Time of Day I Test?
Unlike pregnancy tests, morning (first morning urine) is not the best time to collect samples for ovulation tests, as LH is synthesized in your body early in the morning and will not appear in your urine until the afternoon. The ideal time to test is in the afternoon, around 2pm, though testing may safely take place from 10am to early evening. Be sure to test at the same time each day. Also, reduce your liquid intake around 2 hours before testing as a diluted liquid sample can prevent or hinder LH detection.
Why Do I Need to Test at the Same Time Every Day?
LH is produced by the pituitary gland and is present in the body at all times. To recognize when a surge in LH is occurring, you must first establish a baseline ‘non-ovulating’ LH level. Because LH is synthesized in your body early in the morning and will not appear in your urine until the afternoon, your results will not be consistent if you test at different times of the day and may led to a false positive result.
What Should the Results Look Like?
Once the reaction time of the test is complete (about five minutes), colored lines will appear in the test region of the strip. All tests have a “control” line that indicates whether the test is working or not. If a “control” line does not appear, the test strip is defective and another test strip should be used. Ovulation test results will always show two lines. An LH surge is indicated if the “test” line is equal or darker than the “control” line.
What If the Second Line is Lighter Than the Control Line?
Ovulation tests function differently than pregnancy tests. A positive result (indicating an LH surge) is indicated by a test band that is of equal or greater intensity (equal or darker) than the control band. A negative result for the LH surge is indicated when the test band is of lesser intensity (lighter) than the control band or cannot be seen. A faint line does not indicate a positive result for an LH surge. While a faint line on a pregnancy test may indicate a positive result, a faint line on an ovulation test is always negative.
Is it Possible to Get a False Positive Result?
There are some rare medical conditions (Turner syndrome, Swyer syndrome) which cause elevated LH levels. Women suffering from PCOS (Polycystic Ovary Syndrome) experience elevated LH levels which do not lead to ovulation. Women with PCOS may have elevated LH in their urine throughout their cycle, causing a false positive result. LH levels are unaffected by most over-the-counter and prescription medications, although Clomid may cause false positive results. Consult a doctor if you are unsure about your medications.
For women with PCOS, a fertility monitor is a good option. While the initial expense is much more, you will save money in the end on ovulation kits.
Can I use Ovulation Tests as a Contraceptive Method?
No. An ovulation test will tell you if you are likely to ovulate within 24-48 hours. It is possible for sperm to live for several days after sexual activity. It is therefore not “safe” to engage in sexual activity after a negative test result, since you may experience an LH surge the following day (and ovulate within 24-48 hours) and pregnancy may result.
