Tracking ovulation: temperature and LH tests

A temperature chart and an ovulation test measure different things. Temperature rises after ovulation; a urine test looks for a surge of luteinising hormone, or LH, involved in releasing an egg. Neither is a complete assessment of your fertility.

Before buying either, decide what you want from tracking. You might want a record to discuss with your clinician, or prefer to leave the thermometer in the drawer. Choose an approach that fits your life.

Temperature is mostly a look backwards

Basal body temperature, often shortened to BBT, is your temperature at rest when you wake. After ovulation it rises and remains higher for the rest of that cycle. The rise gives a clue about ovulation after it has happened; it cannot give advance notice of egg release.

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

A chart can be difficult to interpret. The Office on Women’s Health lists fever, poor sleep, alcohol and activity before taking the reading among things that can change temperature. The American Society for Reproductive Medicine (ASRM) describes daily BBT tracking as often unreliable. If the chart is unclear, ask about the method before drawing conclusions about your ability to conceive.

Alongside the reading, note anything about that morning you want to discuss at an appointment. Leave a missed reading blank. You could write, “I was awake much 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. The hormone helps trigger ovulation, which is why the kits are used when planning the timing of sex. They measure a hormone signal rather than directly observing an egg being released.

LH kits can be misleading if you have PCOS. ASRM describes persistently raised baseline LH in this condition as a reason urine LH tests can produce 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 cannot answer every question about fertility. The CDC describes pregnancy as a process involving egg release, fertilisation, movement through a fallopian tube and implantation in the womb. A home LH reading tells you about only a small part of that process.

Choose how much to track

The NHS gives a practical approach that does not require finding an exact ovulation day: sex without contraception every 2 to 3 days. Its advice says people aged 39 or under following this pattern are likely to become pregnant within a year. Your own experience may differ from that general guidance.

If tracking fits your life, you can bring the record to an appointment. If it has become an unwelcome daily task, tell your clinician that too. Ask what information would actually change the next step before committing to more measurements.

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 absent while you are trying. CDC advice identifies these as reasons not to delay seeking care. The NHS also advises speaking to a GP if pregnancy is taking longer than expected.

Before your visit, you could put your temperature readings and kit results alongside your period dates. Label what you actually recorded and what you are unsure about. Ask the clinician which of those records, if any, they want you to keep.

Bring the product name, any readings you have and your main question. Useful wording is: “I’m getting repeated results I don’t understand. Would tracking help here, or do I need a different assessment?”