Fertility Testing for Women
Ovulation Testing > Predictor Kits
An Ovulation Predictor Kit (OPK) is another test that patients can use at home, functioning similarly to a home urine pregnancy test. OPKs measure the urinary level of luteinizing hormone (LH), the hormone which triggers ovulation. Typically, LH levels rise rapidly in the 24 hours prior to ovulation. OPKs detect this rise, and are useful in helping couples know when to optimally time intercourse. The optimal time for intercourse is the day following the positive test.
If menses occur within 12 days of the positive OPK result, the luteal phase may be too short to sustain a pregnancy, and a patient should consult their physician.
Optimizing your OPK test:
- If you have regular, predictable menses, begin testing 17 days prior to the day your period is likely to start. For example, in a 28 day cycle, ovulation most likely occurs around cycle day 14 (within 2-3 days around cycle day 14); the LH surge will precede this by 1 day, therefore begin testing on cycle day 11 (28-17) to maximize the chance that you detect your surge.
- Testing should occur around the same time each day. Most test kits will instruct individuals to test with the 2nd urination of the day. However, the LH rise is most likely to be detected if testing occurs in the mid afternoon, between 3-7 pm.
- While fluid restriction is not necessary, excessive fluid intake causing very dilute urine may limit the ability to detect LH in the urine.
- Ovulation is likely to occur within 12 – 36 hours after a positive test.
- The best time to have intercourse is the day after a positive test.
Below is an example of a classically positive OPK.
(If you have questions about whether your OPK is really positive or not, we can determine this with simple blood tests.)
In our experience, relatively few women have classically positive ovulation predictor kits like the example here. Frequently, the LH surge looks more like the middle drawing. You may only know this after the kit darkens and the next day it fades… If this happens, have intercourse on the day it fades!
If you are uncertain if your test is positive, give us a call. Remember, simple blood tests can confirm whether this is a true LH surge or a false positive result.
See Serum Progesterone for more Ovulation Testing information