Q&A Index > Ovulation Prediction Kits (OPKs)
How do Ovulation Prediction Kits (OPKs) work?
Ovulation Prediction Kits have become quite popular and can be quite useful to help you find your fertile time. OPKs work by measuring the presence of Luteinizing Hormone (LH) in your urine. A surge of LH which is sent to your ovary causes your ovary to produce enzymes which in turn causes the dominant follicle to rupture and release the egg into the Fallopian tube. This is ovulation and it is expected to occur within 24 hours of the surge of LH. An OPK is thus expected to be positive the day before you ovulate.
Following a few guidelines can help you get the most out of your OPK:
- Like any product, follow the manufacturer's instructions carefully.
- If you do not test every day from before you expect to be most fertile, you may miss the surge. Likewise, if you test too late, you may miss the surge. Also, it may not be possible to tell if you are about to ovulate or if you just ovulated since you will have increased LH in both cases. Usually, though, the positive OPK means that you are about to ovulate.
- Testing daily once you have started to test is the best strategy since your first positive OPK result probably means that you are about to ovulate and your last positive OPK, if you get more than one, may mean that you just ovulated. Since OPK packages include only a limited number of test strips, timing when to start testing is crucial.
- If you use OPKs, use the Fertility Friend OPK optimizer to help you choose when to start testing to make sure you do not waste tests and so that you can get optimal results. Based on your average cycle length and previous cycles entered in Fertility Friend, if applicable, the OPK optimizer can tell you when to begin testing so that you will not miss your opportunity but you will not waste tests either.
- Follow the manufacturer's instructions about the time to take your OPK. First morning urine is usually not the best for OPKs since your LH surge usually begins in early morning when you are still sleeping and may not be apparent in your first morning urine. If you test in the early morning, you may miss your surge entirely since LH levels may already be reduced by the next morning. Late morning or early afternoon is usually best unless the instructions suggest otherwise.
- Record your OPK results as positive in the data entry page of Fertility Friend if the test line is as dark as or darker than the control line. Record your results as negative if the test line is lighter than the control line.
- Do not rely exclusively on OPK results to time intercourse as you may not see an LH surge (positive OPK) even though you may be fertile. Your increased fertility begins before you see a positive OPK result since sperm can live in the reproductive tract for a few days in fertile cervical fluid.
- Once you see a positive OPK, keep having intercourse until ovulation is confirmed by a sustained thermal shift.