First let's recap what OPKs are and how they work. OPK is short for Ovulation Prediction Kits.These tests pick up the Luteinizing Hormone (LH) surge that is produced just before ovulation. Just like a Home Pregnancy Tests (HPT), these tests come in different forms; strips, cassettes or midstream.
When is the best time to test?
This all depends on how long your cycles are. Use the following table as a guide line as to when to start testing.
This all depends on how long your cycles are. Use the following table as a guide line as to when to start testing.
| Cycle | Start Day |
| 21 | 5 |
| 22 | 5 |
| 23 | 6 |
| 24 | 7 |
| 25 | 8 |
| 26 | 9 |
| 27 | 10 |
| 28 | 11 |
| 29 | 12 |
| 30 | 13 |
| 31 | 14 |
| 32 | 15 |
| 33 | 16 |
| 34 | 17 |
| 35 | 18 |
| 36 | 19 |
| 37 | 20 |
| 38 | 21 |
| 39 | 22 |
The best time of day to test would be late afternoon. Anything from 2pm is advisable until about 8pm. Reason being that LH is more concentrated in your urine later in the day, as opposed to early morning. FMU is not recommended when testing with an OPK.
Try limiting fluid intake before testing, as well as holding your urine for 2-3 hours before.
If you are taking Clomid/Fertomid it is recommended that you do not start testing until a day or two after your last pill. Sometimes these fertility pills can cause a false positive.
How long do I test for?You will need to test until you get your positive result i.e. detecting your LH surge. This can vary from 4 days to 10 days depending on how long your cycles are. The shorter your cycle the less tests you will need. You would most likely “see” your surge within 4-5 days from testing.
What is a positive, I have two lines???
This can be a bit tricky. Since an OPK does not “read” the same as a HPT. A line is NOT always a positive line on an OPK. You will need your test line to be darker than or as dark as the control line. A faint test line only indicates some LH being picked up, not your surge. So keep testing until your test line gets as dark as the control line.
I have my positive, now what?
Once you get detect your surge, you can ovulate 12 – 36 hours after your positive result. (Bear in mind you can wait as long as 48 hours.) Intercourse (BD-Baby Dancing) can take place the day of the positive OPK; you can skip the next day and BD after that. Although you shouldn’t really miss more than two consecutive days of intercourse when Trying to Conceive (TTC). Of course there is nothing wrong with every day either as long as your partner does not have sperm health issues. If you are tracking your Basal Body Temperature (BBT), keep BD until you confirm your thermal shift.
All above Info came from Making Babies
And since it is always easier to compare your OPKs to a picture, here are a few diagrams and pictures of different types of tests that will make it easier to figure out if your OPK is positive or negative.
Another example of an OPK test, same principle.. not positive until the test line is as dark or darker than the control line.
Left (Not Positive), Right (Positive)
Then of course the lovely Smiley face!
