Many have found ovulation predictor kits, luteinizing hormone test strips, and progesterone test strips helpful for understanding their menstrual cycle. But how do they work? Are they reliable? And are they worth the cost?

The first important thing to understand is the hormones of the menstrual cycle and how they change. You can learn more about them in these articles about the follicular phase and luteal phase. But let’s do a quick recap here.

Menstruation

Technically part of the follicular phase, menstruation is when your uterus lining is shed. Sex hormones are generally at their lowest point during menstruation.

Follicular Phase

The follicular phase is the phase in which an egg is prepared for release - or in broader terms, the body is preparing to ovulate. During this phase, follicular stimulating hormone (FSH) triggers the development of the egg, which in turn releases estrogen. Then the increased estrogen triggers luteinizing hormone, whose job it is to trigger the actual release of the egg. It peaks about 12-36 prior to the event of ovulation. 

Ovulation

The event of ovulation lasts for about 12-24 hours. It starts when an egg is released from the ovary and lasts until the egg is no longer viable for fertilization. Each woman only has one ovulation per cycle, though it is possible to release multiple eggs in one ovulatory event (this is how fraternal twins happen!). When you ovulate, your body tells estrogen to simmer down and progesterone to take up the major role for the rest of the cycle.

Luteal Phase

The luteal phase comes after ovulation, but our bodies don’t just forget about what happened with ovulation. During the luteal phase, the follicle that grew and released the egg transforms into the corpus luteum, which releases progesterone in relatively large amounts, and estrogen in much smaller amounts. The corpus luteum lasts either until your next period - or about week 12 of pregnancy if you become pregnant during the cycle.

At-Home Hormone Tests

There are plenty of different types of hormone tests, and even some monitors you can use at home to test your hormones. We won’t discuss the monitors today, so we’ll stick to luteinizing hormone (LH) strips, ovulation predictor kits (OPKs), and progesterone (PdG) strips.

LH Strips

LH strips measure the luteinizing hormone in your urine. In order to interpret them, you control the test line to the control line. If the test line is as dark as or darker than the control line, your LH is high enough to consider it positive. 

In order to use LH strips, you should start testing about 7 days after you start your period. Once you know your cycle better, you can start using them 3-5 days prior to expected ovulation, or when you start experiencing peak-type cervical mucus (if recording mucus). You should use urine from early afternoon as LH takes about 4-6 hours to show up in your urine. Making sure you record the result within the test’s instructed limit (usually 5-15 minutes), you can take note in your head, mark it in a chart, or even take a picture to record the result.

Once you get a positive result, continue testing your LH until 3 days after your last positive. In this time, you should also see a temperature shift if you ovulated.

Pros

• Inexpensive - when purchased in bulk, these tests are a few cents each.
• The test line isn’t just a binary yes/no, so you can gather when your surge took place (the darkest line) even if you get multiple positive tests

Cons

• Some women don’t experience a high enough LH to make the test “positive”, in which case the darkest test line should be considered positive
• Sometimes you may experience an evaporation line or try to interpret outside the window and get an incorrect result.
• LH strips only test your luteinizing hormone - they don’t confirm ovulation has happened, only that your body is attempting ovulation

OPKs

OPKs are simplified LH strips. Rather than interpreting which line is darker than the other, OPKs give you a Yes or No result, telling you if the test is positive (high LH) or negative (below threshold LH). 

To start using OPKs, start testing about 7 days after you start your period. Once you know your cycle better, you can start using them 3-5 days prior to expected ovulation, or when you start seeing peak type cervical mucus (if also recording mucus). You should use urine from early afternoon as LH takes 4-6 hours to show up in your urine. Then, record the Yes or No result.

Pros

• Binary answer - hard to misinterpret

Cons

• Expensive - especially compared to LH strips
• Binary answer - little added information about which test registered the highest amount of LH
• LH strips (and by extension, OPKs) only test your luteinizing hormone - they don’t confirm ovulation has happened, only that your body is attempting ovulation

PdG Strips

PdG strips test the level of progesterone in your urine. Around day 5 of your cycle, you will need to take a baseline test to compare later tests to.

Unlike LH strips, PdG strips are only accurate with first morning urine. A positive result is also the opposite of LH strips - you want the test line to not appear at all (or be incredibly faint, below your baseline test). Because you’re comparing to a baseline test, you should keep a record of at least the baseline tests in photos.

PdG strips can be an additional confirmation of ovulation - to LH strips, temperature, and/or cervical mucus observations.

Pros

• Tests basic progesterone levels at home
• Can help you understand if you have low progesterone and get further tests with your provider

Cons

• Expensive - since most companies are still developing best practices and growing, the cost for a single test is relatively high. In addition, you do need to retake your baseline test every few months.
• Interpretation is the opposite of both LH strips and pregnancy strips, so a little harder for some people to remember.
• Difficult to get in some countries.

Are these tests accurate?

Yes, these urine tests are usually highly accurate. However, as noted, positive OPK or LH test strips don’t necessarily mean you are ovulating - just that your body is attempting it, and your LH levels are high. Some conditions, such as polycystic ovary syndrome (PCOS) can cause elevated LH consistently, so may make it difficult to use LH strips. 

Progesterone strips are a little bit harder to understand, mostly because they aren’t as well-known.

These tests can be used in any intention of family planning, but they’re especially useful for casual charters trying to conceive. They’re easy to use, although cost may be prohibitive. But they indicate when you’re likely to ovulate, and the progesterone strips also help you confirm ovulation and identify low progesterone issues if present.

Ultimately, these are more tools in your hands when you're charting your fertility - such as using Tempdrop for basal body temperature measurement, and recording your cervical mucus observations. These tests can be incredibly useful in your fertility awareness journey when paired with these other primary signs.