Before taking one, read all the instructions thoroughly, sometimes the recommendations are different. I will explain how I use them and which of the instructions are safe to ignore.
First I would like to explain how they work. They detect lutenizing hormone, or lh. This is given off by the pituitary gland and "surges" once a follicle is a good size to release an egg. Lh is always present in small amounts, and can fluctuate daily. The amount needed to make the follicle release the egg is around 20 mIU/ml. This is the sensitivity of most tests, however some will be positive at 25, and others not until 40. Its hard to tell which ones are how sensitive.
In a normal cycle the brain first sends follicle stimulating hormone, or fsh, in pulses to the ovaries. It starts to mature the follicles (fluid filled sacs that surround the eggs) and over time one or two are selected to be the dominant follicles. So these are the ones that continue growing. They produce estradiol, when it gets to a certain level, about 200pg/ml per follicle, its considered and estrogen surge. At this time, if you are using a ferning microscope, or the Clear Blue Digital Advanced opks, you will see full ferning on the scope, or a flashing smilie face on your opk. This does NOT mean your lh is surging yet. This is not a positive opk just yet. This is the warning that an lh surge is soon to follow, and you are having what they consider "high fertility". Usually about 2-3 days the estrogen will send a message to the brain and then the pituitary gland will send the lh to the ovaries. This serves as a final growth spurt and helps the eggs burst out of the follicles. Again, if you are using the Clear Blue Advanced, you should now have your solid smile. This IS a surge,and you have now reached your "peak fertility".*
Now, for actually using the tests. Kits can come in packages of 5, 7, 10, and 20. Wondfos and other strips sold online, usually called internet cheapies or ics, can be sold in many different combinations and are usually the cheapest option at around $.20-$.25 a strip. You can also get them with their pregnancy tests too so you have them available when the dreaded tww is over. The Dollar Tree also sells them in one test packages at $1 each. If you only need a few, or maybe want to confirm here and there when you think you have a positive on another brand, this is a good way to go.
Step one is to figure out what day to start testing.Here is a handy chart. If you have long irregular cycles, stat testing according to your shortest cycle length. You may need to get more than one kit if you dont pick up a surge by the end of the pack. I always recommend Wondfos to everyone since they are so cheap, very accurate, and you get a large supply (I go for the 100 packs).
Next, find a good hold time. Most ladies I know use second morning urine after holding and not drinking too much water for about 3-4 hours. For me personally (since I dont drink a lot of water) 2 hours works best. Most tests will look a little off, and like they are positive when they arent, if your urine is too concentrated. Too diluted, or not holding long enough, could hide a surge.
FMU or first morning urine is never a good idea unless you are using digital tests. FMU can cause too concentrated urine, leading to a test that looks positive, or the LH may not have built up in your urine yet and would show negative when you are surging. Its a good idea to test twice so you get the beginning of your surge, making for better timing. Another few hours hold in the afternoon is great. I picked 9-10 am and 2-4 pm.
Reading the results can be difficult. They are not like a pregnancy test where a second line means positive. You will be comparing shades of lines. Both having light test line, and no test line are normal. LH is always there in slightly fluctuating amounts. This is also why its not a great idea to get your hopes up when you see a darker negative after a light one. That doesnt always mean a positive is coming soon. Its yes or no, thats all you have to focus on. A positive will be when the test line (always near the dip strip) is as dark as, or darker than the control line (always closer to the handle).
Digital Tests
As far as I know, the digital tests are usually set at around 40, but they will show as positive if your test picks up a level that is higher than your previous days tests. In my opinion, while this works for some women, it seems pretty inaccurate. A lot of ladies will use these once in a while to confirm a cheaper opk, but if you've got a low surge, and no other previous data for the test to go by, it could give you a false negative. On the contrary, it could pick up slight normal variations and turn positive before your surge has actually peaked. Leading you to believe you've had your surge far sooner than you did, and if you were only using opks and not temping to confirm, this could cause you to prematurely stop having sex, and therefore missing your o date all together.
This is what they say about their testing algorithm.
Here is a link to an answered question from Clearblue on this. Here is an excerpt.
"Clearblue Digital Ovulation Tests are strictly looking for a rise in LH.
The threshold that must be reached is 40 mIU/ml of LH. This product
is
not designed to detect LH on the first test. For accurate results,
you
should begin testing on the correct day according to your cycle
length...
The reason we recommend to start testing according to the chart in the
leaflet is because if your surge is lower than 40 mIU/ml, the test is
able
to adjust to your personal hormone levels and still detect the
surge."
Here is their number for more questions 1-800-321-3279
* A tip for those using fertility friend and Clear Blue Advanced opks. You can record your readings on the monitor section. Flashing smile equals high, and solid equals peak.
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