How Long After a Positive OPK Will You Ovulate?

Marie-Claire De Villiers
By Marie-Claire De Villiers
Head and Shoulders Photo of Michelle Meyer
Edited by Michelle Meyer

Published August 4, 2022.

Smiling woman holding up an ovulation test

If you're using an ovulation predictor kit (OPK) at home, you want to be sure about what to expect from it. The OPK tests your urine for luteinizing hormone (LH), which is released in an extra surge by your body as a trigger to ovulation.

How to Use an OPK at Home

Luteinizing hormone is always present in your body and supports your fertility. Start to use the test when you anticipate you might be entering the ovulation stage in your menstrual cycle. This would be after your period ends and before you reach mid-cycle (between day 7 and day 15).

Use the test by following these steps:

  1. Urinate in a small cup.
  2. Dip the test stick into the urine, or hold the stick under the stream of your urine. The best time to take the ovulation test is in the morning (the first time you pass urine) so that the hormone is not too diluted by a large volume of liquid.
  3. Wait a few minutes for the test to take effect on the stick.
  4. Check the two lines which show on the stick. The control line shows you've done the test. The other line, the test line or ovulation indicator, shows the presence of LH.
  5. The result is positive when the test line is darker than the control line. Therefore, you will ovulate within the next three days.

However, the test line showing LH is not as sensitive and definite as it could be. You might see a line that is dark at the edges or just dark on the top. Ideally, the indicator line on the ovulation text should not be faint, but dark and solid to give you a clear idea that an ovum is about to be released.

Women who are anovulatory may use an OPK to track results after inducing ovulation.

How Long You’ll Ovulate For After a Positive OPK

The day of ovulation varies for individual women, depending on the pattern of their menstrual cycles. Some women have shorter cycles, some ovulate later than others. Your ovulatory phase is indicated by increased cervical mucus, a rise in body temperature, sensitive breasts, increased libido, and possibly low abdominal pain. But the positive OPK test result is helpful because it shows that your ovulation is about to happen within the next three days - or it might be happening at that instant. When you ovulate, the ovum (egg) is released from the follicle of the ovary in a burst, moving towards the end of the fallopian tube. This is the ideal territory—and time—for it to be fertilized by healthy sperm. The ovum only lives for 12-24 hours and starts to disintegrate after that, moving into the uterus and passing out of your body.

The test is meant to detect the hormone before you ovulate, so that you can use your fertile days for conception.

Ovulating The Same Day As a Positive OPK: Is It Possible?

It is possible to ovulate on the same day as a positive OPK, but beware of assuming this is always the case. A positive OPK only tells you that your body is releasing a high level of LH. However, infertility may also be indicated by a high LH level, for example polycystic ovarian syndrome (PCOS). In rare cases, the surge does not indicate you have ovulated. Usually, the surge in LH only lasts eight to 20 hours, after which you may ovulate. On the other hand, some women do ovulate on the same day as the LH surge, so it is possible to ovulate on the same day as the positive OPK.

How Long Do LH Levels Stay High During Ovulation?

The level of LH only stays high for eight to 20 hours. It's promoting ovulation, that's really its only function. The level decreases after the ovulation phase.

The Best Time to Have Sex After a Positive OPK

Your positive OPK result shows that you have entered the window period of fertility. Three to six days leading up to ovulation, including the ovulation day itself, is the best time for getting pregnant. Sperm live for up to five days, so even when you have sex at the first indication of a positive test, the sperm will still be active if you ovulate three days after that. It's best to have sex once a day during this fertile phase, and preferably in the morning when the cooler conditions produce the healthiest sperm.

By using an OPK test, which predicts ovulation with 97% accuracy, you have a good indicator of your ovulation. This knowledge of your fertile window helps you plan to conceive.