This post helps answer what a basal body thermometer is, how you use a basal body thermometer, and how using a BBT can help detect pregnancy or ovulation on your BBT chart.
A basal body thermometer can take the guesswork out of pinpointing when you are ovulating. Knowing when you are most fertile helps increase your chances of getting pregnant fast.
We offer Ovulation thermometers in all our Fertility Home Test Kits, ovulation and pregnancy tests.
Please read the basal body thermometer instructions carefully before using the thermometer for the first time.
Instructions for our basal body thermometer
Before using, please disinfect the probe first.
To switch it on, press the ON/OFF button next to the display; a short beep will sound, indicating that the basal body thermometer (BBT) is operational. At the same time, the thermometer runs a self-check test, during which all the digital segments appear on the LCD.
The basal body thermometer is now ready for use when the letters ‘Lo’ and a flashing ‘C’ or ‘F’ display. If the ambient temperature is below 32 C or 89.6 F, then ‘Lo C’ or ‘Lo F’ will appear on the LCD, and if it is more than 43 C or 109.4 F, then ‘HI C’ or ‘HI F’ will appear on the LCD.
The current temperature is displayed continuously during the reading, and the ‘C’ or ‘F’ symbol flashes. The measurement is completed when a constant temperature value has been reached. The temperature value is considered constant when the temperature rises less than 0.1 C within 16 seconds.
A beep will sound four times when the constant temperature value is reached, and the ‘C’ or ‘F’ symbol will stop flashing. The highest temperature measured appears on the LCD. However, please note that this thermometer is a maximum thermometer, i.e. the displayed temperature can increase slightly if measurement continues after the beep. This is particularly the case with axillary measurements, should a temperature value be recorded approximating the core body temperature. In this instance, please note the description under ‘Methods of measuring temperature’.
When the measurement is completed and you have recorded your temperature, please turn off the basal body ovulation thermometer by pressing the ON/OFF button. After the temperature has been displayed, the thermometer will also shut off automatically after 10 minutes.
When to take your basal temperature
- Check your temperature as soon as you wake up before you leave bed.
- Check your temperature at the same time each day.
- Note any differences on your chart/app if your sleep was disturbed.
- If you get less than 3 hours of consecutive sleep, your temperature is considered inaccurate that day — note this.
For more information on when to use the ovulation thermometer
What type of thermometer should I use for basal body temperature?
A BBT must be accurate to 0.01 degrees Celsius and read as 36.50, 36.51, etc. If your ovulation thermometer is not accurate to a tenth degree, you may miss out on the slight changes in your basal temperature.
What other methods can be used to detect ovulation?
Ovulation can be detected in many ways. The symptoms of ovulation are often small and require careful monitoring.
Where to buy a good basal thermometer?
We offer our great ovulation thermometers by themselves or in our Fertility Home Test Kit, which includes a large range of ovulation tests, pregnancy tests, Conceive Plus fertility lubricant and the best basal thermometer in Australia.
Our most popular pack is our Major Fertility Kit which includes
50 x Ovulation Strip Tests
10 x Pregnancy Strip Tests
1 x Ovulation Basal Thermometer
Ovulation Thermometer & Memory Function
Switch the ovulation thermometer off, then press the ON/OFF button for about 2 seconds. The last measured value with ‘C’ or ‘F’ will appear automatically on the LCD. This display is visible when the ON/OFF button is held down. The reading is only over-written when a new temperature value is recorded.
Where do you put a basal body thermometer?
It is important to remember that the body temperature reading depends on the site where it is measured. For this reason, the measurement site must always be specified to ensure a correct temperature reading is recorded.
Methods of Measuring BBT Temperature:
In the mouth (oral)
There are different heat zones in the mouth. Generally, the oral temperature is 0.3 C to 0.8 C lower than the rectal temperature.
To ensure that the reading is as accurate as possible, place the thermometer tip to the left or right of the root of the tongue.
The Basal Body Thermometer tip must have constant contact with the tissue during the reading and be placed under the tongue in one of the two heat pockets at the back; keep the mouth closed during the reading and breathe evenly through the nose.
Do not eat or drink anything before the measurement. The usual measuring time is approximately 50 to 70 seconds.
In the Rectum (rectal)
This is the most accurate method from a medical perspective because it comes closest to the core body temperature.
The ovulation thermometer tip is inserted carefully into the rectum for a maximum of 2 cm. The usual measuring time is approximately 40 to 60 seconds.
Under the Arm (axillary)
Placing the basal thermometer in the armpit measures surface temperature that can fluctuate by around 0.5 C to 1.5 C from rectal temperature readings in adults.
The usual measuring time for this method is approximately 80 to 120 seconds. However, it should be noted that an exact reading cannot be obtained if, for example, the armpits have been allowed to cool.
If this is the case, we recommend extending the measuring time by around 5 minutes to obtain the most precise possible reading that corresponds as closely as possible to the core body temperature.
How to Change the Measuring Scale (only for switchable type)
Turn the unit on to switch the display between C and F on the Basal Body Thermometer. Hold the ON/OFF button for 2 seconds, and the display will show another scale.
Cleaning and Disinfection
The best way to clean the thermometer tip is by applying a disinfectant (e.g. 70% ethyl alcohol) with a damp cloth.
- Do not allow the Basal Body Thermometer to come into contact with hot water
- Do not expose to high temperatures or direct sunlight
- Do not drop the thermometer. It is neither shock-proof nor impact-resistant
- Do not bend or open the device (except the battery compartment)
- Do not clean with thinners, petrol, or Benzenel
- Only clean with water or disinfectant
- Do not immerse the waterproof thermometers under water 15cm for longer than 30 minutes
- The thermometer contains small parts (battery, battery compartment) that children can swallow. For this reason, do not leave the thermometer unattended in children’s hands
- Avoid bending the thermometer tip
- If the ambient temperature is over 35 C, dip the thermometer tip in cold water for approx. 5 to 10 seconds before measuring the temperature
- With children in particular, persistent fever must be treated by a doctor- please contact your doctor!
Battery Replacement for your Basal Body Thermometer
The battery is empty and needs replacing when the”battery” symbol appears on the right of the LCD.
Remove the battery cover and replace it with a battery (preferably non-mercury) of the same type.
Please ensure the environmental protection of your Basal Body Thermometer. Batteries do not belong to domestic waste. Please hand them in as special waste at the collection point or the municipal recycling material centre.
This symbol on products and accompanying documents means that consumed electronic products must not be mixed with conventional domestic waste.
Take these products to the corresponding collection points for correct treatment and recycling, where they will be accepted free of charge.
Please contact your local authorities for more information on the closest collection point.
Type: maximum thermometer
Measurement range: 32.00~ 43.00°C
Measurement accuracy: +/- 0.10°C 35.50°C~42.00°C
Ambient temperature during use: (5~35)°C, ≤80%RH
Battery Type: Alkaline manganese battery, type LR41, 1.5V, service life minimum 100 hours under continuous operation
Weight: Approx. 12g
Explanation of Symbols
The battery is empty when a square is flashing in the bottom right-hand corner.
Lo°C or Lo°F: Temperature under 32°C
Hi°C or Hi°F: Temperature over 43°C
This ovulation basal thermometer is initially calibrated at the time of manufacture. If this thermometer is used according to the operation instruction, periodic re-adjustment is not required.
The calibration check has to be carried out immediately. If there are indications that the product does not keep the defined error limits or the calibration properties could have been affected by intervention or any other means.
Please also observe any national statutory regulations. Competent authorities or authorised service providers can perform The calibration check on your Basal Body Thermometer. A test instruction for calibration checks can be provided to the relevant authorities and authorised service providers on request.
A basal body thermometer can help detect pregnancy or ovulation. Use an Ovulation thermometer to detect ovulation & get pregnant faster.
Evan is the founder of Fertility2Family and is passionate about fertility education & providing affordable products to help people in their fertility journey. Evan is a qualified enrolled nurse and has expertise in guiding & managing patients through their fertility journeys.