Using Ovulation Tests to Predict Fertility

Using Ovulation Tests to Predict Fertility

Ovulation tests - or ovulation predictor kits (OPKs) - are excellent tools for predicting ovulation, a woman's most fertile time during her menstrual cycle. Unlike BBT charting, ovulation tests anticipate ovulation - not just confirm that ovulation has taken place.

Ovulation tests work by detecting luteinizing hormone (LH). Just preceding ovulation, women experience an "LH surge" - a sudden, dramatic, and brief rise in the level of luteinizing hormone. Ovulation tests detect this LH surge, allowing you to accurately predict when you will ovulate. A positive result on an ovulation test means that the woman will most likely become fertile over the next three days - with peak fertility at 36 hours following the LH surge.

How do OPKs Work? Luteinizing Hormone, the LH Surge, and Ovulation 

At the beginning of the menstrual cycle, the body begins to produce follicle stimulating hormone (FSH). FSH facilitates the formation of a follicle on one of the ovaries. The follicle contains and nurtures the egg. When a follicle has adequately matured, a surge of Luteinizing Hormone (LH) causes the follicle to burst and release the egg into the fallopian tube - the moment of ovulation.

Throughout the menstrual cycle, a small amount of LH is produced - but during the middle of the cycle LH briefly and dramatically increases. Elevated quantities of luteinizing hormone facilitate ovulation - and OPKs detect this LH surge through anti-LH antibodies contained in the sensitive testing membrane of the test.

The LH surge is, alas, very brief - and in order to detect the LH surge, a woman needs to test at the right time of the month - and 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 detected, successful fertilization is most likely to take place one to three days following the LH surge - with peak fertility at 36 hours post-LH surge. Since this ovulation "window" only opens once per month (and the unfertilized egg has a short 24-hour life-span) predicting ovulation accurately is very helpful when trying to become pregnant. Below, you will find information on getting the most out of your ovulation tests (and visit our Ovulation Test FAQ for more testing tips).

Advanced Testing Tips and Facts: Answering Common Questions about OPKs


Using OPKs and Interpreting Ovulation Test Results

Ovulation tests come in two formats: test strips and midstream tests. To use the ovulation test strip, you fill a container with urine and hold the test strip in the container for several seconds. With midstream tests, you hold the test in your stream of urine. Both test formats are equally reliable. Always read ovulation test kit instructions carefully.

With most home ovulation testing products, the "reaction time" of the test is five minutes. At five minutes, you can interpret the tests. All tests have a "control" color band (or color line) that indicates whether the test is working or not. Also, the control band provides a color/intensity baseline by which to interpret the "test" band results. The "test" color band indicates a positive or negative result (please refer to the graphic below).

A positive result (indicating an LH Surge) is indicated by a test band that is of equal or greater intensity (equal or darker) than the control band. A negative result for the LH Surge is indicated when the test band is of lesser intensity (lighter) than the control band or cannot be seen. A negative result means the LH level of the urine sample is at or near its normal level and that the LH surge is not in progress. Remember, there is always some quantity of LH in your system, so a light color band in the test region is NOT an indicator of a positive result.


How do I Determine when to Begin Testing?

To determine when to start testing for ovulation, you must first do a little calculating. Use the Cycle Chart below to figure out when to begin testing for your LH surge.

First, determine the average length of your menstrual cycle. The length of the menstrual cycle is the number of days from the first day of menstrual bleeding to the day before bleeding begins on the next period. Determine the usual length of the menstrual cycle over the last few months. Then, refer to the Cycle Chart to determine on which day of the menstrual cycle to begin testing.

Your Cycle Length

Day to Begin Testing

21 days Day 5
22 days Day 6
23 days Day 7
24 days Day 8
25 days Day 9
26 days Day 10
27 days Day 11
28 days Day 12
29 days Day 13
30 days Day 14
31 days Day 15
32 days Day 16
33 days Day 17
34 days Day 18
35 days Day 19
36 days Day 20
37 days Day 21
38 days Day 22
39 days Day 23

Read More About:

> Ovulation Test FAQ: Testing Tips and Tricks
> Saliva Based Ovulation Predictors
> Ovulation FAQ: Frequently Asked Questions About Ovulation
> Pregnancy Testing
> OvaCue Product Review


Hi ladies-
I'm confused about the results from my Clearblue Easy OPK. I've been testing since CD 9, got a High Fertility reading on CD 11 and a Peak Fertility on CD 12 (did an insemination). Out of curiosity, I kept testing. CD 14-15 were negative, but just yesterday (CD 16) it read as a High Fertility again. Took a HPT because I've heard OPK can sometimes read HCG, but it came back negative. Can anyone offer insight into what is going on?

Thanks! vs

I had a miscarriage at 6wks. This past month, my midwife Told me to ttc right away because your supposed to me more fertile.
So I got opk tests to know when I would ovulate. I tested CD15
Negative, tested CD16-CD19 with positives. Ttc CD,15,16,17,

Here's my question I thought you were suppose to ovulate 12-36 hrs after first test. So, now what? Does this mean I haven't ovulated? Or ovulated and why is my LH surge still positive?

New to TTC. OPK today at 6pm, just wrapped up round one of "makin babies" Night all, wish me luck tomorrow!!

hi ladies pls i want to share my experience with unprescribe clomid and i really need ur advice, am 28 yrs and i have two lovely daughter 4 & 2yrs old.
i conceive them naturally, i dont have any fertility issues, i used to get pregnant whenever i want to.
i have two miscarriage last year and i was very depress, so i search the internet on how to have twins,
so i came across clomid my doctor will not give me cox i have no fertility problem.
and the reason why i want twins is bcos my 2 daughters was deliver thru c-section and i only have 1 more chance of c-section.
i have a very regular period of 28days and i used to ovulate cd15 every other month.i use clomid from 3-7 and i ovulate on cd13 and i was very scared bcos the slippery
egg white is alot dat i thought all my eggs has been squeeze out. 1 day after ovulation i have the most horrible abdomen pain of my life, my stomach was very hot and is like my stomach is been squeeze like a wet clothes, i cant walk properly for 3 days. the next cycle my period was 1 day late i still have the horrible pains till cd 14 and i have lh surge but no ovulation. my egg refuse to release, the nest cycle again was 31,28,30 and still detect lh surge but no ovulation.the opk used to be positive on cd 14 but no release of egg. cox i know when when am ovulating. i use to discharge clear slippery white egg and is around 7;15 in the morning or 5;15 in the evening.iusevitex,epo,multivitamin,and vitamin b6 for this cycle to regulate my period, hope it will work
pls should i go to my doctor and explain all dis to her. cox am 100% sure i stop scared dat i am run out of egg or my ovaries has been damage. pls any advice.

Ladies - the best way to predict when you are fertile is to track your BASAL BODY TEMPERATURE!! Home ovulation tests are a great supplement, but by tracking your temperature you can be certain your entire cycle is healthy and on track and know exactly when you are ovulating. Look it up - tons of info is available online!!

Still confused when it comes to the "you have 48 hours to get pregnant". If you receive a smiley, are you ovulating that day, or is it the day after?? Should you BD that same day or the next?
I received a "smiley" on August 4th, around 6am. We didn't try until the next day, August 5th (due to my husband's work schedule), around 3pm. We didn't try the day after either.
I got AF on August 14th (which was 4 days early), and it ended on August 20th, but I then had brown discharge along with ewcm From August 20th-27th, which is odd, because I never had that after AF for such a long span.
I started with the HPT'S, all negative of course!
I should get my next AF around Sept. 10th. My last negative HPT was yesterday, so I'm done Sad
The reason I kept on with the HPT testing was because I had a period while pregnant with my last child and didn't get a positive result until a month later and had brown discharge as well.
Any Input about the CB Easy OPK would be greatly appreciated!

I been using Answer Ovulation Test n mines always showing negative...Sad

For all of you who do not want to waste money on expensive OPKs when you are unsure of when to expect ovulation, you can buy them in bulk on ebay for dirt cheap. The last order I placed was for a pack of 25, for around $6 including shipping. This goes for HCG test strips as well (pregnancy tests). Happy TTC, and baby dust all around!

I have irregular cycles that can range from 28 - 60+ days. I have been pregnant 4 times. The first time would have been a 28 day cycle, the next two times would have been a 6 week cycle, and the last one, that ended in a miscarrage would have been a 10 week cycle. Since I am so irregular, I have no clue when I ovulate and when I should take an OPK test. I have learned about cervical mucus and Basal Body tempature. If you chart or even just pay attention to your cervical mucus, when it is the clear, egg white look, then I know to try the OPK test. The last 4 days I have the egg white mucus and took the OPK test. The morning of day 2 it was nagative, I didn't get a positive until 10 pm on day two and another one at 8 am day three, but by the afternoon of day 3, the LH surge was gone. If you are not sure when to test, then you may want to learn to pay attention to the other symptoms that your body is telling you and the right time of the day is important. If I where to have just taken it the morning of day two, then the afternoon of day 3, I would have missed it. Good luck to all!

I have a 2/12 yr. old and had a miscarriage in August of 2010. We have been trying ever since using the digital ovulation tests. Each month i get about 3 days where it is positive and we try before during and after it is positve. Still nothing. Has anybody had this same situation or any ideas about getting pregnant after a miscarriage? I have some friends who have gotten pregnant right away after a miscarriage and so I'm wondering if something is wrong with me?

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Format: 5/19/2019
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By TTC veteran and mother of two, Elizabeth Andrews.