What is a T/C Ratio on My Ovulation Test?

Ovulation T/C ratio reading on the Premom app

Updated July 21, 2022 | By Teri Karl

You have the Premom app, and you’re ready to get started tracking your ovulation. However, you soon get confused with the number on your app ovulation tests reading, a.k.a. the T/C ratio on the ovulation test result.

What on Earth is a T/C ratio?

Typical ovulation tests have 2 lines: the test line (T), and the control line (C). The T/C ratio simply compares the color intensity of the T line to the color intensity of the C line.

When looking for your LH peak, the app looks for a ratio of 1.0 or higher, when the test line is as dark as or darker than the control line, indicating your test is positive.  A test line lighter than the control line will be less than 1.0 and may not be considered your LH peak day so could be considered a negative test.

T/C ratio on a ovulation test strip

In addition to giving a positive or negative result, ovulation tests can do so much more by helping you find your LH surge by showing an increase or decrease in LH levels as you continue to test.  Though they will not give you an exact LH level (only Premom quantitative tests can do this), they can give you an idea of fluctuations you can expect in your personal ovulation cycle, even helping you recognize the approach of your surge as your levels near 0.5 and above.

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How Should I Read T/C Ratio 

It’s important to know that the exact T/C ratio value is not necessarily important; rather, your goal is to find your highest T/C ratio, also known as your peak, in order to predict your ovulation day.

If you are using the Premom app, the app will take care of the T/C ratio reading for you when you take a picture of your ovulation test in the app. To achieve optimum results, we recommend using Easy@Home or Premom ovulation test kits which are designed to be used with a Premom ovulation tracker app.

A visualized fertile window explanation

To further support your TTC journey, there are many other tools such as fertility expert-designed cycle analysis reports and cycle comparison reports which will give you insights into your cycles based on your ovulation testing results.

When taking a test, always look for the last, darkest test line. Aim for the standard peak ratio of 1.0, but know that some women do peak lower (between 0.8 and 1.0), and others may peak higher than 2.0! 

Since ratios can vary from woman to woman and even cycle to cycle, the key is to keep testing, even after what appears to be a “positive” or “peak” to make sure you’ve found your true peak and that your LH surge is over. In other words, keep testing until you see your LH levels heading back down and staying down. The Premom app is also looking for this and will not designate “peak” until the uploaded test after your peak is in fact a lower T/C ratio. 

Still have questions? In your Premom app, tap “FAQ” in settings for other common questions or tap “Ask an Expert” to get a personalized answer to your specific questions from a fertility expert.

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FAQ

Q: How do I read my T/C ratio on my ovulation tests?

A: You can let the Premom app do the job for you!  The app will automatically compare the color of the test (T) and control (C) lines which creates the T/C ratio.  A ratio of 1.0 or higher, when the test line is as dark as or darker than the control line, indicates a positive test. You’ll always look to monitor the progression of the T/C ratio, you’re looking for the last, highest level to pinpoint your LH peak day. It’s important to note that an LH peak can vary from woman to woman and cycle to cycle, it can be less than 1 or more than 1, what matters most is the highest LH reading compared to the rest of each cycle.

Q: Do the numbers of my T/C ratios reflect my fertility?

A: Not necessarily.  The T/C ratio simply reflects the color difference between the test (T) and control (C) lines on your ovulation test, indicating positive or negative.  If you are unable to find an LH peak after testing twice daily for an entire cycle, it could be beneficial to reach out to your doctor. Also, note that women with different values of T/C ratio can all successfully ovulate whether they have an LH peak at 0.8 or an LH peak at 2.3, it’s the last darkest day of ovulation testing that indicates your LH peak, and thus your predicted ovulation 24 hours later. 

Q: Can the T/C ratio on my ovulation test tell me my LH hormone level? 

A: No, the T/C ratio simply reflects the color difference between the test (T) and control (C) lines on your ovulation test, indicating positive or negative.  If you are interested in a numerical level of LH as opposed to the T/C ratio, try using the Premom quantitative tests.

Q: What would be the ideal T/C ratio for successful ovulation?

A: There is no exact number that indicates successful ovulation.  A different T/C ratio will trigger ovulation for each woman.  Your goal is to find your highest T/C ratio (LH peak ) meaning it is the last, darkest day in the series while ovulation testing. After your peak day, your T/C ratio will swiftly decrease and not peak again until the next cycle.  Ovulation typically follows an LH peak within 24-36 hours.

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