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Temperature tracking (BBT) when trying to conceive

The tiny morning rise that confirms you ovulated.

Fertility & TTC5 min readDeep dive

Written by the Splash teamSources checked

On this page 5 sections
  1. Quick answer
  2. How big is the rise?
  3. How to take it
  4. Things that throw readings off
  5. Sources

Quick answer

  • BBT rises slightly after ovulation and stays up until your period.
  • Measure before getting out of bed, same time daily, with a basal thermometer.
  • It confirms ovulation after the fact – best used alongside mucus and LH tests.
  • Temps staying high past your period date can hint at pregnancy.

Your basal body temperature is your body’s resting temperature. After ovulation, the hormone progesterone nudges it up a little and keeps it there until your next period. Track it for a few cycles and you can see, pretty clearly, whether and roughly when you ovulated.

How big is the rise?

Small! Cleveland Clinic says the shift is usually somewhere around 0.2–0.6°C (0.4–1°F). That’s why you need a basal thermometer that reads to two decimal places.

3 days
Temps staying higher for 3 days in a row suggests ovulation has happenedSee sources

How to take it

  1. Keep the thermometer by your bed.
  2. Take your temperature as soon as you wake – before you get up, talk or drink anything.
  3. Measure at about the same time every day, in the same place (usually your mouth).
  4. Log it in the app from day 1 of your period.
  5. Keep going for at least three cycles to spot your pattern.

Things that throw readings off

  • Alcohol the night before
  • Poor or broken sleep
  • Illness or fever
  • Stress
  • Travel across time zones
  • Some medicines
  • Breastfeeding
MythBBT tells you when to have sex this cycle.
Fact

The rise happens AFTER ovulation, when the fertile window is closing. Its superpower is showing your pattern so you can time things better next cycle.

  1. Period

    Temps typically sit in your lower range.

  2. Follicular

    Lower temps continue. Some people see a small dip just before the rise.

  3. Ovulation

    Look for the shift: a sustained rise over a few days.

  4. Luteal

    Temps stay higher. If they stay up past when your period is due, it may be time for a pregnancy test.

Sources

  1. Cleveland Clinic – Basal body temperature
  2. NHS – Natural family planning (fertility awareness)
  3. Cleveland Clinic – Ovulation

Written by the Splash teamSources checked

This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US). How we write and check articles.

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