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The Complete Guide to Ovulation Testing


ovulation testing

Understanding when you ovulate can be a crucial element in getting pregnant. Especially if you are actively trying to conceive, knowing when you are at your most fertile will help you identify the time period you are most likely to conceive. 


Using an ovulation test, you can pinpoint your most fertile days. In this complete guide, we cover everything you need to know about ovulation testing, from 21-day progesterone blood tests to urine-based tests and saliva ferning tests.


Let’s delve into the ins and outs of ovulation testing!


  • What is Ovulation?
  • Types of Ovulation Tests and How They Work
  • How to Use Ovulation Tests
  • Additional Information About Ovulation Testing
  • Find the Right Ovulation Test for You with Home Health

What is Ovulation?

Ovulation is the process of one or more eggs being released from the ovaries. This is triggered by certain hormones such as luteinising hormone (LH), estrone-3-glucuronide (E3G), oestrogen, and progesterone. 


Each month, approximately 3 -30 eggs mature inside one of the ovaries. The largest of these eggs is pushed out into the pelvic cavity and travels down to the uterus via the fallopian tube. The egg will survive here for about 12-24 hours without being fertilised. If the egg does not become fertilised by sperm during this time, you will start your menstrual period approximately two weeks from this time. 


This process is when you are at your most fertile. Typically, this short window only lasts about six days each month, so it is important to identify when this period of time is for you if you are trying to conceive. 


One way to easily find out when you are ovulating is to use ovulation tests. 

Types of Ovulation Tests and How They Work

There are a few ovulation tests available that measure different hormones that trigger ovulation. From a 21-days progesterone blood test to urine-based ovulation predictor kits and saliva ferning tests, here’s a closer look at each test in detail. 

21-days Progesterone Blood Test

Progesterone is the hormone that aids in building up the lining of the uterus where a fertile egg would implant. If an embryo doesn’t implant in this time period, progesterone levels will begin to decrease over the next two weeks, and your period will begin at the end of this time.


A 21-days progesterone blood test kit or CD21 progesterone test specifically measures the amount of progesterone in your body. Progesterone is at its highest after ovulation, at around the 21-day mark. This is why you should take this blood test to confirm ovulation on the 21st day of your cycle, as this will confirm whether you are ovulating at this time. 

Urine-based Ovulation Predictor Kit 

A urine-based ovulation predictor kit (OPK) analyses the amount of luteinising hormone (LH) in your body. The level of LH in the body increases as early as one or two days before ovulation begins, with the peak level of LH about 12 hours before the egg is released from the ovary. Although LH is always present in urine, the level of LH surges every month, triggering ovulation. A urine-based OPK detects the higher level of LH in your body and relays the result that you are ovulating. 


Some urine-based tests also detect estrone-3-glucuronide (E3G), another hormone present during ovulation. When oestrogen is broken down in the body, E3G is formed and present in urine at the time of ovulation, providing another indicator that you are ovulating. 

Saliva Ferning Test

You can also test if you are ovulating via your saliva. A saliva ferning test uses a small microscope to measure the salt level in your saliva. During ovulation, the amount of oestrogen in your system increases, contributing to a greater salt level in your saliva. When saliva dries, it crystallises, creating a fern-like pattern. If you are not ovulating, your saliva will simply dry in blobs.

How to Use Ovulation Tests

Generally, you should use an ovulation test a couple of days before you think you begin ovulating. As ovulation typically begins about 10-16 days before your next period, you can easily measure your predicted ovulation by tracking your periods using an app or marking it on a calendar. 


However, not everyone’s menstrual cycles are the same! For example, if you have a 28-day cycle, you might begin ovulation around day 14, but if you have a 35-day cycle, ovulation could start on day 21. Using an ovulation calculator to help you work out the stages of your cycle can be helpful. 


If you have an irregular cycle and tracking doesn’t seem to uncover any type of pattern, there are other indicators that suggest you are ovulating. One indicator is your cervical mucus. If your discharge is more slippery and has a consistency similar to egg white, this can indicate you may begin ovulation soon. This is a good time to use an ovulation test to check!

How to Use a 21-days Progesterone Test

21-day progesterone tests should be used on the 21st day of your cycle. This number is based on a 28-day cycle, so you may need to alter this if you have a cycle of a different length. 

There are two types of progesterone ovulation tests: a home kit and one conducted by a doctor. However, both tests use the same method of collecting a blood sample. In an at-home test kit, you must complete a finger-prick test to collect the blood sample needed. This blood sample will then be sent to a laboratory for testing. 

How to Read Progesterone Test Results 

Depending on the laboratory your blood sample is sent to, the criteria, ranges, and units may slightly differ. You should refer to the information on the box if you are using an at-home test kit. Typically, ovulation blood test results might look like: 


  • 30-65.5 nmol/L = Ovulated
  • 15.2-30 nmol/L = Potentially ovulated, but could have conducted the test too early
  • 0-15.2 nmol/L = Not Ovulated 

How to Use Urine-based OPKs and Understand the Results

Urine-based OPKs involve collecting a urine sample by either collecting it in a cup or urinating directly onto the test stick. Lines should then appear on the test, which may correlate with different coloured bands. These bands will indicate whether a surge of LH has been detected in your urine. Digital ovulation tests are more advanced and may show symbols rather than coloured bands. 


You should always follow the instructions of an OPK to ensure you receive an accurate result. For example, some test kits might specify that you should use your test kit on the first urination you have that day, or it may say to test during the late morning or early afternoon. 

How to Use a Saliva Ferning Test Kit 

Saliva ferning test kits can be easier to use than alternative kits. This is because you only need to collect a saliva sample. You can do this by either placing some saliva onto the slide using a stick or your finger or by licking the slide itself. It is best to do this first thing in the morning before you have eaten or drank anything. 


Once you have collected your sample, you must wait for the saliva to dry and place the slide under the provided microscope. If you are ovulating, you will see your dry saliva sample crystallise and form a fern-like shape. However, if your saliva dries in a blob and there is no pattern, you have not begun ovulation.

Additional Information About Ovulation Testing

Some other factors to consider when taking an ovulation test include: 

  • Paracetamol and other common drugs: If you have taken paracetamol or any other common drug before using an OPK, your results should not be affected. 
  • Some hormone or fertility medications can change results: For example, if you are taking Clomid or contraceptives such as the oral contraceptive pill, your results may be affected. You should inform your doctor if you are taking any of these medications before you take a 21-days progesterone test. 
  • You may need to reduce the amount of liquids you drink: If you are using a urine-based OPK, you may need to reduce the amount of water or other liquids you drink before taking the test to ensure your urine isn’t diluted which can also affect your results. 
  • As with all tests, not all OPKs are 100% accurate: Although these ovulation tests are reliable, there is also a chance that the level of different hormones may not be detected. Additionally, a saliva ferning test can be hard to interpret, making it difficult to reach a conclusive result. 

Find the Right Ovulation Test for You with Home Health

If you are trying to conceive, it is important you understand when you are ovulating. With the range of ovulation tests available, you can choose the best type of test that suits you! From digital urine-based OPKs, traditional urine-based ovulation tests, and saliva ovulation testing kits, you can find an ovulation testing kit with Home Health. 


How to confirm ovulation with a blood test

You can use a 21-days progesterone blood test to identify your ovulation period. A blood test to confirm ovulation can be found either at a doctor’s or as an at-home test kit. The doctors will either take a blood sample or, using your at-home test kit, you will do a finger-prick to collect your blood sample. This sample will then be taken to a laboratory for analysis. If high levels of progesterone are detected, you may have ovulated. 

How to read progesterone results 

Your ovulation blood test results may differ depending on the laboratory that analyses your blood sample. An example of ranges and what they mean could be: 


  • 30-65.5 nmol/L = Ovulated
  • 15.2-30 nmol/L = Potentially ovulated, but could have conducted the test too early
  • 0-15.2 nmol/L = Not Ovulated 

What should your progesterone level be if you ovulate? 

Your progesterone levels when ovulating can vary depending on what type of blood test you use and the laboratory the blood sample is sent to. However, the general range of progesterone that indicates you have ovulated is 30-65.5 nmol/L.

How to test if you ovulated 

There are a few different tests that you can use to check if you are ovulating or have ovulated, including a 21-days progesterone test, urine-based OPK, or a saliva-ferning ovulation test. 

  • The 21-days Progesterone Test: A blood sample is collected and tested in a laboratory for progesterone levels. 
  • Urine-based OPK: These tests can measure either luteinising hormone or estrone-3-glucuronide in a urine sample. 
  • Saliva Ferning Test: Salt levels are measured using a saliva sample. Oestrogen triggers this increase in salt. 

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