Q. What is an OPK and what can it tell me?
A. OPK stands for Ovulation Predictor Kit.
The OPK is a test that checks your urine for the presence of LH,
luteinizing hormone. Normally, LH is in a steady state, at a low level (negative test). But when it rises very quickly (LH
surge) it stimulates the developing egg (follicle) and ovulation (release of the egg) follows shortly thereafter.
The OPK helps you predict when you are about to ovulate. Ovulation
usually happens within 12-36 hours after the OPK first turns positive.
Q. At what time of the day should I test with my OPK?
A. In general, it's suggested to test in the early afternoon, usually
within a couple of hours before or after 3 p.m. or so.
Many women can have an LH surge after waking up, but it can take
four to six hours for the LH surge to first show up in the urine.
Some women test twice a day, just to make sure they don't miss
the very first surge.
Q. My OPK was positive on CD 12. Today is CD 19 and I still haven't
seen a typical rise in my BBT curve. Could I have a positive OPK without ovulating?
possible to have a positive OPK without ovulating. The OPK does not test for ovulation, but for the LH hormone, which usually
precedes ovulation and which stimulates the egg to ovulate. A positive OPK without ovulation can happen under the following
1. LUFS (luteinized unruptured follicle sydrome) where there is
a surge in LH but no egg is released.
2. Premature ovarian failure
Q. My OPK tests faint in the result window for many days in a row.
Is that a problem?
A. It's normal to always have some LH in your body. It's shortly
before ovulation when it rises significantly. Most tests do not become clearly positive until a certain LH is reached, and
many will show a faint line with lower LH levels. If your result line often has significant color, you should consider trying
another brand, and if it's still positive for many days in a row, then you may want to see your doctor and test your LH levels
on the third day of your next cycle to see if your hormone levels are elevated.
Q. I see a faint line in the OPK test window. Is that positive
and does that mean I will ovulate soon?
A. A line in the OPK that's fainter in the test window than the
control window does not mean you are going to ovulate.
Unlike home pregnancy tests where any line in the result window
indicates a positive, OPKs are only positive if the test-result line is the same color or darker than the reference line.
You should read the manufacturer's instructions to verify if a
positive means that it's the same or darker than the control window.
Q. I had sexual intercourse with my husband late at night, and
the next day my BBT showed was elevated, indicating ovulation the day before. Can I find out whether I ovulated in the morning
or at night?
A. It's impossible to determine from your BBT curve whether you
ovulated at night or in the morning. We can't even be 100% sure of the day. Once there is a typical rise in the temperature,
all we can say is that ovulation probably happened about 24-36 hours prior to that rise.
Q. When and how often should we have sex after the OPK turns positive?
A. The perfect time for sex is the day just prior to the ovulation
predictor FIRST turning positive.
And this may sound like a surprise, but making love only after
first getting a positive OPK may not get you pregnant at all.
Ovulation can happen as early as 14 hours after the OPK first becomes
Let's say you test with the OPK at 8 a.m. and it was negative.
Then, the OPK turns positive at 11 a.m. So ovulation could then happen 14 hours later, at 1 a.m. the next day.
If you test every 24 hours you will only find out about the positive
OPK at 8 a.m. the next day, which may be too late for getting pregnant if you only have sex at that time.
Testing every 12 hours may be more reliable to predict ovulation.
Making love after ovulation won't get you pregnant, so if you rely
on the OPK and you wait to have sex only when the test becomes positive, you may decrease your chances of getting pregnant.
That's why it's generally suggested to make love two to three times
each and every week. That way you are unlikely to miss ovulation.
In addition, you may want to make love once a day when the OPK
turns positive, just to make sure.
Q. We like to time our sex so that we can make love during the
most fertile days. Which is better, OPKs or fertility monitors?
A. There is no proof that timing sexual intercourse based exclusively
on OPKs or fertility monitors actually increases your chances of getting pregnant.
Studies have shown that even in women with regular cycles, ovulation
can happen on many days of the cycle.
Because making love after ovulation won't get you pregnant, it's
suggested that you make love regularly, two to three times a week, every week of the month, if you want to improve your chances
of getting pregnant. You can still make love daily during the 4-5 "fertile" days prior to and during ovulation, but if that's
all you do, then it won't likely increase your pregnancy chances.
Q. I know both ovulation predictor kits (OPKs) and BBT charting
can determine ovulation. But which is a better indicator of actual ovulation?
A. The OPK and BBT curves really function differently.
An ovulation predictor kit changes color before you ovulate, based
on a surge in your luteinizing hormone (LH), usually 1-2 days before ovulation. OPKs usually predict when you are about to
A BBT chart reflects your progesterone level. It's close to zero
before you ovulate and goes up dramatically after ovulation. This is reflected by a rise in temperature after ovulation. Your
basal body temperature (BBT) chart can detect ovulation only afterward, because your temperature goes up only after you ovulate,
usually 1-2 days later.
You can't use a BBT chart to determine when to have sex (or uterine
insemination) that same month, but an ovulation predictor kit can predict ovulation early on.
You must be aware that sometimes neither will work: Both ovulation
predictor kits and basal body temperature/cervical mucus charts can be wrong.
Q. I was told that I may not ovulate. Are there any reliable methods
to detect ovulation and to find out if I am ovulating normally? What are the usual symptoms and signs of ovulation?
following are ways to detect ovulation with some certainty, in order of decreased probability:
A typical temperature rise on the BBT chart.
An endometrial biopsy that shows typical changes 7-10 days after
An elevated blood progesterone level about 7-10 days after ovulation.
Seeing on ultrasound a follicle that measures 18mm+ and not seeing
it anymore several days later and seeing fluid around the ovary.
A positive OPK (ovulation predictor kit).
Mittelschmerz (ovulation pain).
Cervical mucus changes like egg-white cervical mucus (EWCM).
A regular, 28-day-or-so menstrual cycle is usually a good indication
of regular ovulation. But not always. One important way to detect regular ovulation is to keep a menstrual calendar. When
you see your doctor, the menstrual calendar helps to explain your cycles.
Other ways to detect ovulation include checking for fertility signs
such as watching for your mittelschmerz, and evaluating changes in the cervical mucus and the cervical position. But even
with the typical fertile egg-white cervical mucus (EWCM), there is insufficient certainty that ovulation has happened.
The major question is always, "how can I predict ovulation ahead
of time?" Besides calculating your ovulation based on your cycle length, prediction of ovulation is often done with OPKs.
As soon as they turn positive, ovulation usually happens within 12-36 hours. You cannot predict ovulation ahead of time with
the BBT curve.
Obviously, a positive pregnancy test is the very best indication
that you ovulated.