Urine Ovulation Tests work by measuring the hormone LH (leutenising hormone) in a urine sample.
What is LH I here you ask.
LH is a hormone that is produced by the pituitary gland in women of childbearing age. Each fertile month, LH surges or peaks and it it this sudden increase in the level of LH which is the trigger for the ovary to release the egg. After release the egg is able to be fertilised, so by detecting the sudden surge, women can estimate quite accurately when they are fertile in every cycle. This timing is used to maximise the chances of conception by millions of couples trying to concieve each year.
An LH test works by detecting the levels of LH in daily urine samples collected by the woman. Some LH is produced throughout the cycle, so the test cut off has to be set at a level which will only give a positive indicator or positive result, when the peak or surge has occured.
The WHO (world health organisation) recommend 40 miu/ml urine LH for professional LH urine testing. For some women this level is too high and they never get a positive result. As a consequence most commercial home ovulation tests work to 25 or 30 miu/ml for a positive result.
Performing a home ovulation test is simple and easy. The best time to collect a urine sample for LH testing is probably early evening, as first morning samples can miss the surge in LH which occurs generally later in the day.
Sexual intercourse should be timed for the evening of the first positive result and for the following few days. This ensures the best chance of fertilisation and conception during that cycle.
Does an LH surge occur every cycle ? No, especially with increasing age LH can be erratic with one in four cycles missing a detectable surge.
LH surges in some women never result in a urinary peak of 25miu/ml These women may be ovulating normally, but urinary LH detection may not work for them. There is no way around this, and alternative fertility monitoring methods should be sought.
The fact that a surge occurs is the important factor, not the length of the surge. Stop testing as soon as the surge is detected and save any unused tests for the next month.
Some LH tests cost serveral pounds each, but cheaper test strips are now widely available and branded reliable LH test offer highly accurate, low cost testing with professional levels of reliability.