Can i use a regular thermometer for basal body temperature

Basal Temperature

The basal body temperature, a measure of the normal temperature of an average person upon waking, rises as a result of hormonal changes during ovulation. Ultra-sensitive basal thermometers are capable of tracking even the most minute of basal temperature changes. Taking and recording your basal temperature is an easy and straightforward method to track, allowing you to pinpoint the occurrence of ovulation within your menstrual cycle.

Because of the nature concerning basal body temperature, this method will only be accurate if you take your temperature upon waking and at a consistent time. Variance in the time that the temperature is taken each day could cause incorrect results and comparison between your temperatures from day to day. The best time to take your basal temperature is right after waking up, before even getting out of bed. The best way to achieve this is to keep the thermometer within close reach on a bedside table, allowing you to easily access it upon awakening without any unnecessary movements that could cause a rise in temperature.

For the average woman, the normal basal body temperature lies between 96 and 99 degrees Fahrenheit. On the first day of ovulation; however, this temperature drops slightly then rises about half a degree. This rise in temperature, induced by an increase in the production of the progesterone hormone, creates a warmer and lusher environment for conception. Basal thermometers are accurate enough to measure this small temperature rise, allowing for a low-tech and inexpensive way to track ovulation.

Basal Thermometer

A basal thermometer can be used to chart a woman's basal body temperature, thus allowing them to predict their fertile period or ovulation. Although there are different basal thermometers available on the market, digital basal thermometers are your best bet, allowing for better accuracy and easier readings. Some thermometers also include blank basal body temperature graphs for the user to track their temperature over multiple cycles.

Basal Thermometer vs. Regular Thermometer

Whereas typical fever thermometers measure to the tenths place of a degree, basal thermometers measure to the hundredth place. This additional increment provides a more accurate measure, better for measuring the subtle changes in basal body temperature.

Digital basal thermometers are also more reliable to track this variance than even glass basal thermometers. A digital reading is more accurate and easier to read than a traditional glass thermometer, giving the more precise reading essential to this charting method.

In addition to being more accurate, digital basal thermometers are also fast. They can provide a reading in approximately 30 to 60 seconds. Glass basal thermometers, on the other hand, can take up to 5 minutes to give a reading. Digital thermometers are also more durable and difficult to damage, and some will store your temperature in case you do not want to chart it immediately.

Basal body temperature (BBT) is the lowest body temperature attained during a period of rest, and it’s particularly useful in estimating the day of ovulation. A BBT graph shows ovulation after it has occurred, not before, so you could use Flo's online ovulation calculator to predict when you might ovulate, and your basal body temperature data to confirm it.

To determine the best time for sexual intercourse, log and monitor your BBT for a minimum of two to three menstrual cycles. An ovulation pattern will gradually emerge, allowing you to plan accordingly for the days leading up to the next temperature increase.

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BBT-based tracking is a simpler alternative to a gynecologic ultrasound, but it needs to be measured every day for several cycles with no breaks. Basal body temperature usually drops right before ovulation, then increases rapidly. It’s helpful to keep the following things in mind:

• During the follicular phase of the cycle, BBT stays in the lower range, generally between 97 and 98 degrees Fahrenheit (36.1 to 36.6 degrees Celsius) until approximately one day before ovulation, when BBT reaches its lowest point.
• After ovulation, the corpus luteum begins to secrete progesterone. The basal body temperature increases by 0.5–1.0 degrees Fahrenheit (0.3–0.6 degrees Celsius) and plateaus throughout the luteal phase. In the late luteal phase, when the corpus luteum regresses and serum progesterone level decreases, the BBT returns to the lower range either one to two days before or just at the onset of menstrual bleeding.

If a fertilized egg fails to implant, progesterone levels and basal body temperature both return to normal before menstruation.

Fertility experts agree that monitoring basal body temperature is the easiest, most affordable method of detecting ovulation. It’s ideally measured in the morning after at least three to four hours of sleep and prior to any physical activity. 

Throughout the day, BBT fluctuates due to stress, cold, heat, exercise, food consumption, etc. A temperature that is unaffected by these external factors is regarded as the most reliable.

When trying to conceive, take your basal body temperature every morning before getting out of bed. Creating a comprehensive BBT chart can assist you in:

• Understanding the processes your body is undergoing
• Determining your most fertile days
• Predicting menstruation
• Investigating potential hormonal imbalances and reproductive issues

Also, a BBT graph can tell you on which days to refrain from having unprotected sex to avoid conception. Of course, this approach works best when the menstrual cycle is stable, periods are regular, and measurements are accurate. However, several factors (e.g., stress, illness, lack of sleep) make it less than foolproof.

Basal body temperature data is useful for predicting ovulation days. Follow these steps to get an accurate BBT reading:

• Take your basal body temperature every morning at the same time.
• Don’t get out of bed, talk, or engage in any other activities before checking your temperature.
• Always utilize the same type of measurement (orally, vaginally, or rectally). 
• Use the same thermometer every time.
• Make sure you’ve had at least three hours of sleep prior to checking your BBT.
• Log all BBT data on paper or with an app like Flo for at least two to three cycles.

Additional things to remember:

• Of the three options available, rectal readings are considered the most reliable.
• When obtaining BBT orally, put the thermometer underneath the tongue and hold it in place. Keep your mouth closed for at least five minutes (if it’s mercury) or until you hear the signal (if it’s electronic).
• If you opt for the vaginal or rectal methods, the waiting period for a mercury thermometer is only three minutes.
• Never check your BBT in the underarm region, as it won’t provide an accurate reading.

BBT values obtained over a menstrual cycle should be entered into a chart that’s divided into two phases. The vertical dividing line corresponds to ovulation, with your cycle’s first and second phases on either side of the line. 

Changes in basal body temperature seem to result from progesterone’s impact on the body’s thermoregulatory center, as well as fluctuations in estrogen. First-phase BBT tends to stay low and is predominantly affected by estrogen activity. Second-phase BBT, which is noticeably higher, is controlled by progesterone. 

In the absence of pregnancy, basal body temperature usually dips approximately one to two days prior to menstruation. Of course, this may differ from one individual to the next, and it will also vary slightly from cycle to cycle.

Consider purchasing either an electronic or mercury thermometer for gauging basal body temperature. Then, make sure to use the same one throughout the entire measurement period.

Generally speaking, electronic thermometers are safer to use; they signal when peak temperature is reached and store all the information for future reference. In contrast, mercury thermometers must be shaken. (Try to do this the night before so the movements don’t affect your morning BBT.) Also, if a mercury thermometer reading falls between two markings, always choose the lower one.

Struggling with insomnia? Avoid measuring basal body temperature until you’ve gotten at least three to four hours of continuous sleep.

If you work at night, check your BBT in the daytime after a few consecutive hours of restful slumber. Over time, the data on the BBT graph will prove to be far more reliable.

If your basal body temperature remains elevated for more than 14 days after a leap indicating ovulation and your period doesn’t start, this could indicate pregnancy.

When conception has occurred, the fertilized egg implants into the endometrium 6 to 10 days later. This often translates to a steep decline in BBT, as the onset of pregnancy is associated with the release of estrogen. Subsequent progesterone production will soon cause it to rebound.

As a result, basal body temperature following conception may create a triphasic pattern on the BBT graph (i.e., a third temperature level appears).

However, these signs of early pregnancy aren’t infallible. To be on the safe side, consider taking a home pregnancy test or contacting your health care provider for confirmation.

My husband and I stopped using birth control for a few months, but we weren’t trying very actively. I came across FAM (the Fertility Awareness Method) and started charting. I have had two infections of the ovaries in the past connected to my celiac, and I was scared that I might not be able to get pregnant at all. After one month of temp charting, I was pregnant! Didn’t even have to take a pregnancy test because the chart showed so clearly that I had to be pregnant. But I still tested a week ago! I’m 5 weeks at this moment!

A typical BBT graph reveals day-to-day changes. A person’s menstrual cycle consists of two phases (occurring before and after ovulation). A normal basal body temperature chart is biphasic, resembling a bird flying upward. It’ll show the dips in temperature before ovulation and before menstruation (when conception does not occur). Immediately following ovulation, BBT rises and remains high until the premenstrual drop.

The BBT spike in the second phase should be at least 0.5 degrees Fahrenheit (0.3 degrees Celsius) higher than the first-phase BBT. Furthermore, it’ll last for about 10 to 14 days.

Next, let’s dive into the different types of basal body temperature charts and what they indicate.

When a BBT graph displays a steady pattern with no distinct highs or lows throughout the cycle, it could indicate the absence of ovulation. So, if you observe a low basal body temperature in the second phase, you probably didn’t ovulate at all.

This situation isn’t a cause for concern. In fact, some people experience several anovulatory cycles per year, which is completely normal. At other times, a faulty thermometer may be the culprit. Try again with a new thermometer and use an ovulation test. If nothing changes, consult your health care provider. 

When conception does not occur, the BBT chart should show two temperature levels. A low basal body temperature will appear during the first phase, and a high one will appear during the second.

A zigzag-shaped graph with constantly alternating low and high BBTs might point to an estrogen deficiency. This assumes the thermometer isn’t faulty and all logging instructions were followed correctly.

Think about adjusting your diet and paying closer attention to your overall physical and mental health, then continue monitoring your BBT for three more cycles. If you’re interested, speak to a gynecologist about what steps to take next.

If a BBT graph shows a chaotic curve over several cycles, with dramatic temperature increases, it may also indicate a shortage of estrogen. (Dips and spikes in basal body temperature exceeding one full degree are considered dramatic.)

As always, external factors can interfere with BBT tracking results. They include a defective thermometer, inconsistent measuring techniques, or altered mental and physical states due to stress, fatigue, illness, etc. Make an appointment with your provider to follow up on these BBT results.

Basal body temperature data is potentially incorrect when:

• It’s measured at different times of the day or with different approaches.
• You have a fever.
• You’re using certain medications.
• Alcohol was consumed the day before.
• Emotional or physical stress is present.
• The body’s circadian rhythm is disrupted (e.g., by jet lag).
• You sleep with an electric blanket, electric sheets, or a heating pad.
• You’re breastfeeding.
• You’re struggling with insomnia.

Charting BBT is not helpful when taking hormonal contraceptives because these synthetic hormones affect menstruation and ovulation.

By carefully following these guidelines, you’ll be well prepared to achieve the BBT chart results you want! The Flo app offers a great basal body temperature tracker, so be sure to download it today!

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