Seeing that positive OPK is exciting—it means your most fertile time is right now. But many people have questions: Does a positive test mean I'm ovulating right now? How long do I have? When exactly should we have sex?
Let's break down exactly what's happening and how to make the most of this fertile window.
What a Positive OPK Actually Means
Ovulation predictor kits detect Luteinizing Hormone (LH) in your urine. Throughout most of your cycle, LH stays at a low, steady level. Then, about 24-36 hours before ovulation, LH dramatically increases—this is called the LH surge.
When your OPK shows a positive result, it means your LH has surged above the test's threshold. This surge is the signal that tells your ovary to release an egg.
The sequence of events:
- LH begins to rise (you may see lines getting darker)
- LH surges to peak levels (positive OPK!)
- 24-36 hours later, the ovary releases an egg
- The egg lives for 12-24 hours
Your Fertility Timeline After a Positive OPK
Exactly When to Have Sex
Once you get a positive OPK, your optimal intercourse timing is:
🎯 Your Action Plan
Why this timing works: Sperm can survive in the reproductive tract for up to 5 days (though 2-3 days is more typical). By having sex the day of your positive OPK and the following day, you ensure sperm are waiting when the egg releases.
"The best pregnancy rates come from having sperm already in position when ovulation occurs—not from trying to time sex to the exact moment of ovulation."
How to Read Your OPK Results
Interpreting OPK results can be confusing at first. Unlike pregnancy tests where any line is positive, OPKs require the test line to be as dark or darker than the control line to be positive.
Reading Strip-Style OPKs
❌ Negative
Test line is lighter than control line. LH is present but hasn't surged yet. Keep testing daily.
⚠️ Almost Positive
Test line is close but still slightly lighter. Surge may be starting—consider testing again in 8-12 hours. You're likely entering your fertile window!
âś… Positive!
Test line is as dark or darker than control. This is your LH surge! Ovulation is coming within 24-36 hours. Time to have sex!
The LH surge can be short—sometimes lasting only 12-24 hours. If you only test once daily, you might miss it. When you're approaching your expected ovulation date, try testing in the afternoon AND the evening to catch the surge.
What If You've Already Had Sex Before the Positive OPK?
Great news—that still counts! If you had sex in the 2-3 days before your positive OPK, those sperm are already in position and waiting. The fertile window includes the days before ovulation, not just the day of.
In fact, some studies suggest the day or two before the positive OPK have the highest conception rates. So if you've been having sex every other day, you're already well-positioned.
Does a Positive OPK Guarantee Ovulation?
Not quite. A positive OPK confirms that your body tried to ovulate (the LH surged), but it doesn't guarantee the egg was actually released. In most cases, ovulation follows the surge—but occasionally it doesn't.
Situations where you might surge without ovulating:
- PCOS: Women with polycystic ovary syndrome may have elevated LH throughout their cycle or multiple surge attempts
- Luteinized Unruptured Follicle (LUF): Rare condition where the follicle doesn't release the egg
- Stress or illness: Sometimes the body starts the ovulation process but stress interrupts it
If you want to confirm ovulation actually happened, track your basal body temperature (BBT). A sustained temperature rise after your positive OPK confirms ovulation occurred.
When to Stop Testing After a Positive
Once you get a clear positive OPK, you can stop testing for that cycle. Continuing to test will show the line fading as LH returns to baseline—this is normal and doesn't mean anything went wrong.
Some people like to track the full surge (rising, peak, falling) to understand their pattern, which is fine. But for conception purposes, once you've seen the positive, you have the information you need.
Common OPK Questions Answered
What time of day should I test?
LH often surges in the early morning hours, but it takes time to show up in urine. Many experts recommend testing in the afternoon or early evening (between 2-8 PM) for best results. Avoid testing with first morning urine, as you might miss a surge that started overnight.
Should I reduce fluids before testing?
Yes, slightly. Very dilute urine can make the test line fainter. Try to limit fluids for 2 hours before testing, but don't dehydrate yourself. Just avoid chugging water right before.
Why is my test line always somewhat visible?
LH is present in your body throughout your cycle at low levels, so you'll usually see a faint line even on negative tests. This is normal. You're looking for the line to become as dark or darker than the control—that's what indicates the surge.
I got a positive yesterday but it's negative today—what happened?
That's exactly what should happen! The LH surge typically lasts 24-48 hours, then drops back to baseline. If your test was positive yesterday, ovulation is likely happening today or tomorrow. Keep to your timing plan.
Track Your Full Fertile Window
Know when to start testing and when your fertile days are likely to occur.
Ovulation Calculator →The Bottom Line
A positive OPK is your body's signal that ovulation is imminent—typically within 24-36 hours. This is your most fertile time. The best strategy:
- Have sex the day you get your positive OPK
- Have sex again the next day
- Optionally continue every other day for another day or two
Don't stress about hitting the "perfect" moment. Sperm live for days, so having sex in the window around ovulation gives you excellent chances. The positive OPK is your confirmation that timing is right—now relax and let biology do its thing.