There are three types: the simple strip, the digital test with a reader and the dual digital test, which reads estrogen as well as LH. They differ in how much they show you and how much interpretation they leave to you. For value, the book recommends simple strips combined with cervical mucus.
Ovulation tests measure LH (luteinizing hormone) in urine. A positive means an LH surge is underway and ovulation is coming within 24 to 36 hours. The three types differ in how they show you that result.
| Type | What it shows | Good for | Downside |
|---|---|---|---|
| Simple strip (budget) | A test line you compare with the control line | Daily use during the window | Subjective interpretation: “is this line darker than yesterday's, or the same?” |
| Digital with a reader | A smiley face or a clear positive symbol | Those who'd rather not interpret | Doesn't show the upward trend, only “not yet” or “now yes” |
| Dual digital (LH + estradiol) | Rising estrogen (high fertility) and the LH surge (peak fertility) | A more informative reading | Expensive for daily use |
The strip lets you follow the trend if you compare lines day by day, but it asks you to judge them. The digital reader removes that judgment and, with it, the trend: its “not yet” covers every day before the surge, so it can't tell you whether you are getting closer. The dual digital adds an earlier signal, rising estrogen, at a higher cost per test. The book gives Clearblue Advanced as an example of a dual digital test.
The strip and the digital reader read only LH, so both are later signals than cervical mucus, which shows up 3 to 5 days before the LH surge. The dual digital is the only one of the three that also flags rising estrogen.
It depends on what else you track. If you combine tests with cervical mucus and temperature, they add little extra information: they only confirm what the mucus already suggested. If you use tests alone, with no other signs, you're paying a lot for a method of moderate precision.
Whichever type you choose, the timing rules don't change: start 4 days before your expected ovulation and test between 10 a.m. and 8 p.m., with urine held 2 to 4 hours. The book's weekly routine also includes confirming you have enough tests for the window.
Simple strips during the expected window, combined with cervical mucus. Precision: high.
This comparison comes from Chapter 17 of Map to the Positive, in Station II (Attunement). The same chapter gives the start day for each cycle length, the six mistakes that invalidate a test, and the cases where tests don't work well. Station II also teaches you to read cervical mucus and basal temperature, the signs that make simple strips enough.
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