How Accurate are Ovulation Tests?

If you’re trying to conceive, you’ve likely learned a lot very quickly about ovulation: what causes it, and when it is. Identifying when you ovulate is vital to ensuring you can try to get pregnant at a time when it’s most likely to succeed. If you’re trying outside the four-five days before ovulation and twelve-twenty four hours immediately following it, your chances of conceiving are low to non-existent.

That means you’ll be taking a keen interest in anything that promises to track and predict when you (or your partner) are due to ovulate, but you need to retain some critical faculties. Today we’re taking a look ovulation tests and asking if they’re accurate, and if they’re the right option for you.

How Do They Work?

Key to finding out if they’re accurate is understanding how ovulation tests (also known as ovulation predictor kits or ‘OPKs) work. They’re very similar to a pregnancy test: they test urine for a particular hormone, and use that to deliver a positive or negative result.

The hormone ovulation tests are looking for is the LH or luteinising hormone: the chemical that actually tells your ovary to release an egg. This hormone reaches a high level in your body roughly 24 hours before you ovulate, so detecting a spike in your urine levels should be a good indicator that you’re it’s the right time to try and conceive.

How Accurate Are They?

Ovulation tests can be very accurate. They’re calibrated for use on a largely healthy woman with the average levels of LH and other fertility related hormones, so as long as you fit that profile, they’ll a highly accurate result. The best OPKs can offer around 97% predictive accuracy – close to, but not actually perfect.

The problems start to come in if you’re not the average woman.

When Don’t They Work?

Some women simply have a particularly strong surge of LH around their ovulation. This can lead to false positives days before you’re actually fertile, or indeed afterwards! If you fall into this category, be it regularly or only on the occasional month (or if you’re taking fertility increasing drugs) the predictive power of these kits is a little diluted and they become less and less useful.

If you’re living with PCOS your cycles are frequently longer and less regular, which makes it hard to even identify when you should be using testing kits at all. The hormone changes that PCOS brings with it can also cause both false positives and false negatives making these less useful tools.


If these testing kits aren’t a good fit your you, you do have some options. Measuring your basal body temperature and monitoring its dips and spikes can be a much more accurate way to predict your ovulation if opks don’t work for you. This used to rely on you manually taking your temperature and recording it each day, but systems that integrate sensors, apps and computers are becoming available that can life some of the load from your shoulders and help produce a useful result every month!