Ovulation Prediction Kits are quite popular and can be quite useful to help you find your fertile time.
"Advanced OPKs" and Fertility Monitors using the same sticks are also available. These advanced sticks actually measure both Estrogen and LH and provide more advanced notice of ovulation. See below for more details.
Hormones, Ovulation and OPK
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 cause the dominant follicle to rupture and release the egg into the Fallopian tube. This is ovulation and it is expected to occur within 12 to 48 hours of the surge of LH.
A standard OPK is calibrated to detect the onset of the LH surge. Once positive it means that your surge has started and that the egg will be released shortly after.
Typically, the egg is released about 12 to 36 hours after the surge but this timing can vary greatly (denoted on the graph above by the red shaded area showing when ovulation can occur).
From a charting perspective, once the surge has started you may ovulate that day (depending on the timing of the OPK test and your own LH profile it may even have already occurred by the time you test) or up to 48 hours after due to the different timing of the observations.
To really know when/if ovulation actually occurred you will need to track your Basal Body Temperature (BBT). A progesterone test can tell you if ovulation actually occurred but not when it occurred.
A standard OPK is a test stick which has a control line and test line. It is positive when the test line is as dark OR darker than the control line.
Some OPKs include a digital reader that look at the intensity of the lines and simply display a smiley when positive.
Advanced OPKs measure your estrogen level and LH levels.
LH detection provides the same information as the standard OPK. It gives you between 12 hours and 48 hours advanced notice of your ovulation. This corresponds to the Peak/Solid Smiley display.
Using the Estrogen detection capability, these sticks/monitors can also give you a few more days notice of your fertile window (High/Flashing Smiley display).
An advanced OPK displays a Low, High (flashing smiley) and Peak (solid smiley) fertility status based on your hormone levels. Enter this result in the corresponding data entry field (Monitor/Advanced OPK) on Fertility Friend (under Tests).
Note that Fertility Friend analyzes these data entries precisely so make sure to enter your data under the right field.
OPK Usage Tips
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 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.
Reading and Recording Your OPK Test
For more details on reading and recording your OPK including a description of the available fields see the Reading and Recording Your OPK article.
Direito, Ana, et al. "Relationships between the luteinizing hormone surge and other characteristics of the menstrual cycle in normally ovulating women." Fertility and sterility 99.1 (2013): 279-285.
Strauss, Jerome F., and Robert L. Barbieri. Yen & Jaffe's reproductive endocrinology: physiology, pathophysiology, and clinical management . 8th Edition. Elsevier Health Sciences, 2018.