Tracking ovulation: temperature and LH tests

A temperature chart and an ovulation test measure different things. Your temperature rises after ovulation. A urine test looks for a rise (surge) in luteinising hormone (LH), which helps release an egg. Neither is a full check of your fertility.

Before you buy either, decide what you want from tracking. You might want a record to show your clinician. Or you might prefer to leave the thermometer in the drawer. Choose what fits your life.

Temperature is mostly a look backwards

Basal body temperature (BBT) is your temperature at rest when you first wake up. After ovulation it rises and stays higher for the rest of that cycle. The rise is a clue that ovulation has already happened. It can’t warn you before an egg is released.

If you choose to record it, MedlinePlus describes using a suitable thermometer each morning before you get out of bed, at about the same time each day. Write down the reading as it is, even if your chart looks different from an example online.

A chart can be hard to read. The Office on Women’s Health lists things that can change your temperature, such as fever, poor sleep, alcohol and moving around before you take the reading. The American Society for Reproductive Medicine (ASRM) says daily BBT tracking is often unreliable. If your chart is unclear, ask about the method before drawing conclusions about your ability to get pregnant.

Next to the reading, note anything about that morning you’d like to talk about at an appointment. If you missed a reading, leave it blank. You could write “I was awake most of the night” without trying to correct the temperature yourself.

LH kits look for a different signal

Urine ovulation kits look for a surge in LH. This hormone helps trigger ovulation, which is why people use the kits to time sex. They measure a hormone signal. They don’t show an egg actually being released.

LH kits can be misleading if you have PCOS (polycystic ovary syndrome). ASRM explains that LH levels often stay high in this condition, so urine LH tests can give false positives. If you have PCOS, ask your clinician whether these kits are useful for you before relying on a repeated pattern of results.

A kit also can’t answer every question about fertility. The CDC describes pregnancy as a process. An egg is released and fertilised, travels through a fallopian tube and then implants in the womb. A home LH reading only tells you about a small part of that.

Choose how much to track

The NHS gives a practical approach that doesn’t need you to find an exact ovulation day: sex without contraception every 2 to 3 days. It says people aged 39 or under who do this are likely to get pregnant within a year. Your own experience may differ from this general advice.

If tracking fits your life, you can bring your record to an appointment. If it has become a daily chore you don’t want, tell your clinician that too. Before you commit to more tracking, ask what information would actually change the next step.

Take concerns to an appointment

Book a GP appointment in the UK, or see your doctor in the US or elsewhere, if your periods are irregular or have stopped while you’re trying. CDC advice says these are reasons not to put off getting care. The NHS also advises seeing a GP if getting pregnant is taking longer than expected.

Before your visit, you could put your temperature readings and kit results next to your period dates. Mark what you actually recorded and what you’re unsure about. Ask the clinician which of these records, if any, they want you to keep.

Bring the product name, any readings you have and your main question. You could say: “I keep getting results I don’t understand. Would tracking help here, or do I need a different kind of check?”