How Do Ovulation Tests Work?
Ovulation tests (opks, ovulation predictors) function by detecting the reproductive hormone LH – or luteinizing hormone. Just before ovulation, women will experience an “LH surge” – a brief, marked increase in the amount of luteinizing hormone in their systems. Ovulation test kits detect this sudden LH surge, allowing you to predict, with great accuracy, when you will ovulate.
A positive on an ovulation test indicates that a woman will most likely become fertile over the next 3 days – with peak fertility at 24 to 36 hours after the LH, or positive ovulation test. Please note that some fertility medications can confound results (e.g., clomid can cause a false positive ovulation test if you begin testing too early in your cycle). Once you receive a positive result, we recommend having intercourse daily over the next 3 to 4 days.
Let’s take a closer look at how ovulation tests work in relation to what happens in the body and with your reproductive hormones. At the start of your cycle, the body starts to make follicle stimulating hormone (FSH). FSH facilitates the production of a follicle on the ovaries. The follicle holds the ovum, helping it grow and mature. As the menstrual cycle progresses – and when a follicle has adequately matured – an increase of luteinizing hormone (the LH surge) causes the follicle to open and the ovum is released into the fallopian tube. This is the definition of ovulation: the moment the mature ovum is released. And this is why knowing when you ovulate allows you to know that you are fertile.
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It’s important to note that throughout the entire menstrual cycle small amounts of LH may be present in your system. But its during the middle of the cycle (around CD14, depending on cycle length) LH briefly and dramatically “spikes”. As noted above, elevated quantities of luteinizing hormone facilitate ovulation – and ovulation predictors detect this LH surge. The LH surge is very brief and a woman needs to test at the right time of the month, even the right time of day. As LH is produced by the body in the morning, mid-afternoon is considered the ideal time to test.
Once the LH surge has been indicated by a positive result, fertilization will most likely occur 1 to 3 days after the LH surge. You should be most fertile at 24-36 hours after the LH surge. As ovulation only takes place once per month (and the egg has a quick 24-hour life-span) predicting ovulation is a helpful key to becoming pregnant.
- Fertility Testing Guide: Ovulation & Pregnancy
- Ovulation and Pregnancy Test FAQ
- Ovulation Test FAQs
- Fertility & Ovulation Predictor Tests
- How do Ovulation Tests predict fertility?
- How do I interpret ovulation test results?
- How do I determine when to begin testing for ovulation?
- Help using ovulation tests
- How to use your basal thermometer
- Ovulation Microscopes: Instructions & FAQ
- Predicting Ovulation with the ClearBlue Fertility Monitor
- Fertility Charting with a Saliva Ovulation Microscope
- Detecting your “Estrogen Surge” with the OvaCue Fertility Monitor
- A Game Plan for Getting Pregnant with an Irregular Cycle!