OPKs work by detecting the level of luteinizing hormone (LH) in your urine. In general, the level of LH rises just prior to ovulation. Using these kits during the range of possible ovulation times during the month allows you to pinpoint that surge and gives you an accurate estimate of when ovulation will occur.
For women who may be suffering from fertility issues, these kits help determine if ovulation is occurring at all. This can be confusing, but you can still have periods even if you don't ovulate, so even a regular cycle can be marked by an absence of ovulation.
OPK vs. BBT
When OPKs came on the market not too many years ago, they were seen as an important breakthrough in pinpointing fertility. This is because the most common method prior to the availability of measuring LH was basal body temperature (BBT) charting. With BBT, a woman knew she had ovulated when her temperature took a slight but steady rise. The main drawback to that method was that a woman only knew she had ovulated after she had already ovulated. As a result, BBT charts had to be kept over a period of several months and analyzed carefully to determine when she might possibly ovulate in any given time frame so that she could have intercourse before ovulation, which is considered the best time for conception. OPKs tell you beforehand, so you can plan accordingly.
Who Uses Them?
In most cases, OPKs are used by women who are trying to get pregnant, and fertility doctors often recommend them as one tool in the arsenal of fertility tracking. Dr. Angie Beltsos, of Fertility Centers of Illinois, says they do use them and recommend them as they're very helpful in determining the specific days of ovulation. "They aren't a perfect test, but they do help many women hone in on the time that ovulation is occurring," she says. "They can be problematic when there are fertility medications involved, but in general once it starts to turn positive, it's telling you that the surge is going to happen."
Dr. Beltsos says that it's important to be directed in how to use OPKs if you're on fertility medication, because there are different protocol for each procedure and each fertility drug.
OPKs are extremely helpful for those who have normal cycles, which Dr. Beltsos defines as between 28 and 32 days. However, those with wildly irregular cycles may find them cost-prohibitive to use. While prices vary depending upon brand and supplier, in general you can expect to pay about $3 to $7 per test for those brands considered the most reliable.
Chrissy Wilson of San Diego, California, says she spent a small fortune on tests because of her irregular cycles. "I needed to test every day, sometimes for months; I could spend easily $200 per month," she says. "Finally, we invested in a computerized fertility monitor for about what it cost us for one month's worth of OPKs. It was definitely worth it for us."
Another feature that most women may see as convenient is one that you have to pee on a stick. And many women find it hard to decipher the results. Most tests have two side-by-side lines, and one line has to be read in comparison to the other. Dr. Beltsos agrees that this can be extremely confusing when the line is not definitive, and she often hears from couples who, even when working together, can't decide if it's positive or not. Dr. Beltsos' solution is to retest.
Tips for Using OPKs
- Figure out the best time of the month to test. To do this, take the number of days in your shortest cycle and count backwards by 14 to 16 days. That is the day to start testing.
- Test between noon and 8 PM. Do not use first morning urine.
- Do not test after drinking large amounts of liquid; hydration can affect the results.
- Once you get a positive test, there is no need to retest.
- Women with PCOS often get false positives. If you suspect that there is a problem, contact your doctor.
- Women who have irregular cycles or plan to use ovulation testing long-term for birth control may want to consider investing in a computerized monitor, which tends to be easier to interpret and may save money in the long run.