Ovulation Predictor Kit: Does It Really Work?

Ovulation Predictor Kit: Does It Really Work?

Millions of women use ovulation predictor tests or OPKs to help when trying to conceive. Generally, they are very accurate but there are times when you could get a misleading result.

How does Ovulation Predictor Kit work?

OPK stands for Ovulation Predictor Kit. OPKs are also known as home ovulation tests.

The most common and affordable type of OPK uses test strips which you pee on or add urine to. To understand when an OPK could be wrong, you have to first understand a little about how they work.

ovulation test positive

After an egg has matured in the ovary, it still has to be released into the fallopian tube.

Ovulation, which is the release of the egg from the ovary, is triggered by a hormone made in the pituitary gland called LH.

Normally, the LH level in a woman’s blood is low. Just before the egg is released, the levels of LH in the blood increase by a huge amount. This is called the LH surge. When the LH in your blood goes through the kidneys, some of the LH will be filtered into the urine.

So, its possible to measure the amount of LH being produced by your body with a blood test in the doctor’s office or by a urine test.

An OPK tests the amount of LH in the urine. If the level of LH in urine is high, that turns the OPK positive and it usually means that ovulation is going to occur in the next 24 hours.

But there are times when a positive OPK may not mean ovulation is near.

  • 1) Women who have PCOS

PCOS is a problem which causes women not to ovulate. Some women with PCOS have high LH levels all the time. For those women with persistently high LH levels, an OPK could be positive all the time.

pcos ovulation test

We recommend that women start testing with an OPK at least a few days BEFORE they think ovulation might happen.

Ideally, the first few days of testing should be negative and then turn positive. If the test is positive from the very first day, you should not rely on it to accurately predict ovulation.

  • 2) Women taking some types of fertility medications

Some injectable medications like Menopur contain the hormone LH. If your dose of these medications is high enough, it could turn your OPK positive without indicating ovulation.

letrozole clomid ovulation test

Oral medications like Clomid or Letrozole work by stimulating the pituitary gland to produce more of the hormones that stimulate the ovaries. It is possible, in the 1-2 days after taking these medications that the LH level could be high enough to cause a positive OPK.

Again, be wary of an OPK that is positive the first day you test, especially if you have just finished a dose of Clomid or Letrozole.

Another medication that can cause your LH to be temporarily increased is Lupron.

  • 3) You already ovulated

The LH surge has three phases where the levels of LH are increasing, steady and then decreasing. The whole thing could take a few days and so your OPK could be positive for several days.

lh hormone surge ovulation

Ovulation occurs within 24 hours after the start of the LH surge. If you started testing too late in your cycle, your might have ovulated some time in the past. 

Having intercourse more than a day after ovulation has a very poor chance for producing pregnancy.

  • 4) Pregnancy and other sources of hCG

LH is very similar to another hormone called hCG, which is the hormone produced during pregnancy. Depending on the OPK you use, it is possible to see a positive result on your OPK from having too much hCG in your blood.

This is also true if you are taking injections of hCG. The higher the levels of hCG in your body, the greater the chance that it could cause the OPK to be positive.

Some types of tumors can also produce hCG, but this is pretty rare.

  • 5) Kidney problems

OPKs measure LH in the urine. Any kidney problems that affect how much LH is filtered into the urine could give you a false positive result.

kidney fertility ovulation

  • 6) Menopause

If a woman has passed the menopause, there are no more viable eggs in the ovaries. The pituitary gland produces higher amounts of two hormones: FSH and LH. The high LH levels will cause a positive OPK. Post menopausal women cannot become pregnant on their own.

  • 7) Surgery to remove the ovaries

Just like the case of women who are in the menopause, if a woman had surgery to remove her ovaries, the pituitary gland will also produce more FSH and LH.

  • 8) Pituitary tumors

Although they are pretty rare, some types of tumors in the pituitary gland produce LH which would give a positive result on your OPK.

  • 9) Dehydration

When a woman becomes dehydrated, her body conserves fluid. As a result, she make less urine and the urine she does make is more concentrated.

dehydration fertility ovulation

If it is concentrated enough, it could cause an OPK to turn positive. An OPK is generally a highly accurate way to predict ovulation. If you have a negative test that turns positive after a few days, it is highly likely you are about to ovulate.

If your OPK is positive all of the time, then it is recommended that you be evaluated by a fertility specialist.

Looking for other tips to improve your chances for trying to conceive? Check out our fertility supplements and treatments.