The basal body temperature (BBT) varies from person to person and also depends on where you measure it. You can measure your basal body temperature orally, vaginally, or rectally.
Measurement of the temperature vaginally or rectally provides higher temperatures than measuring orally. It is therefore important that you always measure in the same way and in the same place. Measuring orally is the standard way of measuring, and we do recommend it due to hygienic reasons, but you choose.
Happy measuring!