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Basal Thermometers – Tips for Use

Tips for using a basal thermometer to help you conceive.

A basal thermometer is a sensitive thermometer that tracks your body’s minutest temperature shift. A basal body temperature (BBT) thermometer is used to chart your basal body temperature chart to determine your fertile period or when you ovulate. There are two types of BBT thermometers available, glass and digital. A digital basal thermometer is a better option as it is very reliable and returns your temperature much quicker than a glass basal thermometer. Most basal thermometers come with a blank basal body temperature chart that you can use to record your readings. You can also download a our free basal body temperature chart to use.

A basal thermometer is more reliable and accurate than a simple glass thermometer since glass thermometers are only accurate to .2 degrees Fahrenheit. You really need it to be accurate to .1 degrees Fahrenheit. The main advantage of the digital basal body thermometer over a fever measuring body thermometer is speed. The basal body digital thermometer is more accurate than a fever based thermometer, and it only takes 30-60 seconds. In addition, a digital basal thermometer is harder to break and remembers the temperature for you if you don’t want to chart it immediately.

Charting your basal body temperature is also easy. Simply put, what you are doing is taking your temperature first thing each day and plotting the temperature on a chart. What you are looking for is to see a temperature shift of at least .4 degrees Fahrenheit after ovulation making your chart biphasic. This means that your chart should show low temperatures before ovulation in the follicular phase, and higher ones after ovulation in the luteal phase.

Here are some tips to help use your basal body thermometer with optimum accuracy:

1. Use your basal thermometer first thing in the morning before you get out of bed.

To avoiding forgetting you can leave your thermometer at your bedside within easy reach so you don’t have to move much to get it. If you use a glass thermometer, make sure you shake it down before going to bed.

2. Try to take the temperature at as close to the same time each day as possible.

You may need to set an alarm to be accurate. Staying within a half hour either side of your average time is a good idea because your temp can vary with the time. For example, if you usually take your temperature at 6 a.m., it is fine to take your basal body temperature between 5:30-6:30, but the closer to 6 the better. The normal variation is by up to .2 degrees per hour. It may be lower if you take your temperature earlier than average and higher if you take it later than average time.

3. It is best to use your basal thermometer after 5 hours of uninterrupted sleep.

The minimum limit is 3 hours.

4. You can use your basal body thermometer orally, vaginally, or rectally.

But always stick with the same method for the entire cycle.

5. You should try to place the basal body thermometer the same way each day

Meaning, try and place the basal thermometer in the same location of your mouth, same depth vaginally or rectally.

6. If you see a drop in your temperature, have sex.

Some women, not all, have a temperature drop when they ovulate and then see the temperature jump following the dip. If you see this drop, it is a good idea to have sex in case you are ovulating. Otherwise continue using your basal body thermometer throughout the cycle for accurate results.


Last modified: February 10, 2013


The information provided here should not be considered medical advice. It is based on the average experience of women trying to conceive and may not be what you may be experiencing. It's not meant to be a replacement for any advice you may receive from your doctor. If you have any concerns about your cycle or our ability to get pregnant, we advise you to contact your doctor.