Fertility · 5 min
Basal body temperature basics
BBT usually confirms ovulation after it happens. It is a rear-view mirror, not a green light.
Not contraception
Basal body temperature tracking alone is not a method of contraception. It should not be used alone to prevent pregnancy. LunaLoop is not a fertility-awareness contraceptive product. If you need pregnancy prevention, talk with a clinician about methods designed for that purpose.
The idea
After ovulation, progesterone can raise resting temperature by a small amount (often around 0.2–0.5°C). A sustained rise across several days suggests ovulation has already occurred.
How to measure
Take temperature at the same time each morning, before getting up, with a basal thermometer. Sleep disruption, alcohol, illness, and inconsistent timing scatter the chart. Missing days is normal — look for a pattern, not perfection.
Limits
BBT does not predict ovulation in advance. If you are trying to conceive, combine methods and clinical guidance rather than relying on any one number.
Sources
- Mayo Clinic Staff. Basal body temperature for natural family planning. Mayo Clinic, 2026.
- American College of Obstetricians and Gynecologists. Fertility Awareness-Based Methods of Family Planning (FAQ024). ACOG, 2019.
- Bull JR, Rowland SP, Scherwitzl EB, Scherwitzl R, Gemzell Danielsson K, Harper J. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. npj Digital Medicine, 2019.
- Jerilynn C. Prior, MD, FRCPC. CeMCOR profile and menstrual cycle / ovulation research program. Centre for Menstrual Cycle and Ovulation Research (UBC).
Educational information for general awareness. This article has not been individually reviewed by a clinician for you, and it is not medical advice.