They work in a similar way to HPTs. They are a urine test, usually you collect your urine in a cup and then you either dip a strip into it, or drop some urine into a little 'cassette'. You can get mid-stream tests, but they are less common, and more expensive. Two lines +, one line -! You usually need to do a few each month, starting from just before when you think you will O.
I have tried a few brands and found them all to be good, but by far the cheapest are the lullaby conceptions (ad at top of this screen) which you purchase online. Otherwise you can get them at the chemist, priceline, supermarket etc. I think Fortel and Confirm are also good. (But more $$$)
Good luck! Ask away if you have any more questions!
24 hours or so before ovulation there is a hormonal surge. This hormone is called luteinizing hormone.
The OPK's detect this hormone so you know when you have a +ve test that ovulation will be within 24 hours. That is the best time to get down to buisness
Jazmum - as Sammi said opk's are a nifty little stick that detects your "LH surge" - lutenising hormone surge.
In the first part of your cycle the follicles that hold your ovum begin the process of maturation. When they are mature and ready for business your brain triggers the release of lutenising hormone. Once this LH surge occurs your ovum are released from the follicle, which of course is ovulation.
Ovulation is most likely to occur within 12-36 hours of seeing a positive opk result according to science. However this can't be exact or static. The advice from my gynae is that you begin to make love from when you first see a positive until the sticks turn negative and then a day for good measure! You can have an LH surge but not ovulate - however seeing this surge is a very good indicator of ovulation. Most women will have only 1 or maybe 2 days of true positives in a cycle.
These tests are different from home pregnancy tests in that the test line has to be the same colour or darker than the control line to be a positive. We all have a level of LH hormone in our body all the time (even men!) so it is possible to see a second line throughout your cycle. Women with pcos are likely to have this. Many women will see a 'fade in' pattern whilst using LH strips. This will be a day or so of a second line though not positive then a true positive. It is believed the optimal time to test is at 2pm. It is often recommended that if you test and start to see a second line to do another test 4-6 hours later to ensure that you 'catch' the surge. Having said that for a few women they don't get a true positive and the second line indicates an LH surge. However this isn't so for everyone and is contrary to manufacturers guidelines. However if you do choose to use opk's you will get to know what they mean for your body. I know for me I have had a tough time getting true positives and the second line coming up was my signal of the LH surge. However with a little work I have now had 2 months of true positives.
These tests differ from preg tests also in that you shouldn't use first morning urine. This is because as you know the first morning urine is concentrated and this could give you a false positive result.
I think opk's or LH strips are a fabulous tool to check fertility. They really pin point fertility down to a day or two which is really handy. They can take a few cycles to get the hang of and know what they mean for your body. LIke someone else said the Lullaby strips are really economical and a great product!
Thanks so much everyone. You are all being very helpful. I went to the chemist today and picked up my thermometer, and my folic acid. Will start charting tomorrow. How exciting.
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How do OPK's work
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