Basal body temperature (BBT) is your temperature at rest. After ovulation, progesterone usually causes a small rise that lasts until your next period.

How should you track it?

• Use a basal thermometer each morning before getting out of bed.
• Measure at roughly the same time, after at least three hours of uninterrupted sleep.
• Record your readings and note illness, disrupted sleep or alcohol use.

What can your chart show?

A sustained temperature rise may suggest ovulation has already occurred. BBT is more useful for looking back at a cycle than predicting your most fertile days. Avoid waiting for the temperature rise to start trying.

What are its limits?

• An unclear chart does not automatically mean you are not ovulating.
• BBT cannot reliably diagnose low progesterone or assess egg quality.
• A one-day dip does not confirm implantation.
• Higher temperatures alone do not confirm pregnancy—take a pregnancy test if your period is late.

If your cycles are irregular or absent, or you are having difficulty conceiving, discuss an assessment with your healthcare provider. When needed, appropriately timed progesterone testing or ultrasound may help assess ovulation.

Your chart is one clue, not a diagnosis.

Longevity Fertility Centre | Calgary & Edmonton