An Honest Review of Fitbit for Menstrual Cycle Tracking

You may know that the Fitbit app has some built in menstrual cycle tracking features, but many people do not know that it has other features that may be useful for menstrual cycle tracking. In this article, I will review the pros and cons of the Fitbit app as it relates to cycle tracking for people who ovulate. For context, I use a Fitbit Charge III.

The most basic feature that Fitbit offers for cycle tracking is recording bleeding dates of menstruation and then displaying a predicted fertile window based on average cycle length.

The pink bar represents the length of menstruation. The blue bar represents a predicted fertile window. The flower symbol represents predicted ovulation.

The user needs to remember to input menstuation each cycle. Once it is inputted, Fitbit will generate the blue fertile window. This fertile window should NOT be used for avoiding pregnancy, as it is only based on cycle length and not real-time fertility signs like cervical mucus or basal body temperature.

Once menstruation is entered, it will also begin a countdown until your next predicted menstrual cycle.

Countdown until menstruation in the app.

Unfortunately, I do not find this basic feature very useful for anyone who has any cycle variation. Even though my cycle length has increased over the last year, Fitbit has not automatically updated my cycle lengths. The app does not appear to be very adaptive without user input.

In addition to tracking bleeding the app offers options for:

  • Mood
  • Plan B (morning after)
  • Ovulation tests (better called luteinizing hormone tests)
  • Cervical mucus (Taking Charge of Your Fertility categories)
  • Cyclical symptoms like acne

It is rather disappointing that the app does not include options to mark pregnancy when it occurs, especially since we know that this changes daily calories burned and heart rate, to name just two effected areas of the app.

A really cool feature that I do like is the ability to show cycle trends like flow intensity and cramps. The same screen that displays this will also let you scroll through all past cycle lengths.

In the settings of this screen, you can also decide to toggle off predictions. For people avoiding pregnancy, I do recommend either ignoring or toggling off predictions in the Fitbit app. The app allows you to choose your current birth control method as well.

Outside of the designed menstrual cycle tracking features, I want to highlight resting heart rate as a potential exciting thing to track for those who are not taking hormonal contraception. Why do you need to not be taking hormonal contraception to utilize the heart rate feature for menstrual cycle tracking? Hormonal contraception suppresses ovulation, and ovulation changes our heart rate charts!

To learn more about resting heart rate and the menstrual cycle, read my previous post here.

You can see my heart rate falling during menstruation around April 10th, and then rise during my fertile window and luteal phase.
Menstruation began when my heart rate dipped below 70 on this chart. Ovulation likely occured around the third raised heart rate in this close-up.

Heart rate in people who are ovulating is at its lowest point during menstruation, rises during the fertile window, and continues to be elevated in the luteal phase.

When heart rate begins to drop again, this is an excellent way to predict menstruation will soon occur. For example, I have been tracking my heart rate in Fitbit for 2 years, and I always bleed when my heart rate dips back down to 70 beats per minute after my luteal phase!

I do think this feature is worth tracking for anyone interested in a more precise period prediction than cycle length. If you have Fitbit premium, you can also find a setting for sleeping heart rate under restoration. This may be more steady than resting heart rate for some individuals.

Lastly, I want to address Fitbit temperature for menstrual cycle tracking. Unfortunately, wrist temperatures are not a compatible parameter for fertility awareness when it comes to avoiding or achieving pregnancy. It can be incredibly erratic. When we track temperature, we want the temperature as closest to the core as possible.

Fitbit does not give precise temperatures, instead it gives deviations from a range. I likely ovulated near 18, 19, or 20 on the photo above. While Fitbit did detect a slight shift, it is not particularly clear, and it dropped back down.

As depicted above, my luteal phase the previous month was extremely undefined, and I could not determine a confirmed temperature shift with it.

For now, I do not recommend Fitbit for precise temperature tracking. Instead, I recommend a basal body thermometer.

Conclusion

Fitbit offers some really unique options for cycle tracking, but it should not replace your birth control or fertility awareness method. The heart rate feature may be useful for identifying cycle phases, but the temperature readings are not suitable for tracking cycle phases.

6 Cycle Comparison: Marquette Versus Billings Versus DOT Fertile Windows

Have you ever been curious what your fertile window would look like in multiple methods?

In this blog, I show 6 cycles with various fertility signs and method interpretation including: the sympto-thermal method (Sensiplan rules), Marquette method, the Billings Ovulation Method, and DOT (a calendar method that was recently purchased by Clue app and is a new FDA approved birth control). I chose to include representation for only studied methods of fertility awareness: sympto-thermal, sympto-hormonal, mucus-only, and calendar method.

All charts are from the Read Your Body app, a flexible app for all methods that I highly recommend!

Some things to know before reading:

  • Marquette allows sex any time of day within their rules. My calculation rule lasts until the end of day 7.
  • Sympto-thermal method allows sex any time of day during first 5 days of menstruation, but the first safe day in the luteal phase must be used in the evening. My calculation rule is day 5.
  • Billings Ovulation Method allows sex in the evenings only and on rotated days in the pre-ovulatory time of the cycle. Days of bleeding where mucus cannot be observed are not allowed. However, since you can have sex any time of day post-ovulation with Billings, sometimes cycle day 1 is available if you have sex before bleeding occurs.
  • DOT allows sex any time of day within their rules. It automatically opens my window on day 7.

Cycle 53

Consecutive Fertile Window for Expected Abstinence:

Billings: 8 days

Sympto-thermal: 12 days

Marquette: 12 days

DOT: 12 days

General remarks: This is an extremely standard cycle in length and mucus patch (the average person will have a 5 to 6 day mucus patch when charting). I believe this is a great example of what methods would look like for someone of the average cycle length.

Cycle 54

Consecutive Fertile Window for Expected Abstinence:

Billings: 9 days

Sympto-thermal: 21 days

Marquette: 15 days

DOT: 12 days

General comments: My average coverline is 96.8 to 97.0, so regardless of earlier high temperatures and some illness I felt confident marking this coverline and temperature shift. Due to continous long, clear-ish mucus, my sympto-thermal peak was extremely delayed. Billings is a sensation focused method so I was able to mark my peak at an earlier time and have less expected abstinence.

DOT gave me a very risky day on this one. It is possible I could have been ovulating near the safe day. However, that would have only left 9 to 10 days for implantation and I had spotting, so whether this truly could have ended in pregnancy is up in the air. Even with well-timed sex, pregnancy will not always occur.

Cycle 55

Consecutive Fertile Window for Expected Abstinence:

Billings: 6 days

Sympto-thermal: 12 days

Marquette: 12 days

DOT: 12 days

General comments: This small fertile window in Billings might look scary to some, but it is not possible to get pregnant when the cervical mucus plug is truly closed. I have about one cycle like this every 13 cycles. I was also using the Kegg device during this cycle which is placed internally and reads electrolyte levels to determine the fertile window. It gave me the same 3 day dip for a fertile window, so I feel even more confident that those days were truly dry. I am missing temperatures on this one because my thermometer glitched and would not give me readings on these days. Sex day 1 was allowed because menstruation didn’t start until 5pm.

Cycle 56

Consecutive Fertile Window for Expected Abstinence:

Billings: 8 days

Marquette: 11 days

DOT: 12 days

General Comment: This was an extremely heavy period so I had no period days available in Billings. Even though the other methods gave me available days, I couldn’t have used them due to the pain, so ultimately the other methods didn’t really help out on more safe days.

Cycle 57

Consecutive Fertile Window for Expected Abstinence:

Billings: 10 days

Marquette: 14 days

DOT: 12 days

Cycle 58

Consecutive Fertile Window for Expected Abstinence:

Billings: 9 days

Marquette: 11 days

DOT: 12 days

General Comments: Marquette monitor missed my peak on this cycle. It misses peak on up to 10% of cycles. I relied on meeting LH rules instead of the monitor. Sex day 1 was allowed because menstruation didnt start until 1pm.

Reflecting on What’s Best for Me

I’m currently on cycle 59 charting, and I have tried a ton of methods. Right now, my ideal method is Billings and LH tests as a bonus marker.

While it may appear that Billings gives less safe days in some instances, what is most important to me is having the smallest consecutive fertile window. Having less expected abstinence actually makes me more likely to follow the rules. I was completely unsatisfied with only being allowed period sex in the sympto-thermal method because I have period pain issues. That means that I basically had no safe days at all in reality before ovulation with sympto-thermal.

I originally felt very enthusiastic about Marquette method. However, after 6 cycles of using the Clearblue Fertility Monitor, I realized that it always caught my LH surge after the cheap LH tests. In addition, it missing my peak even once is frustrating for the cost of the product. For that reason, I have decided to stop using the monitor when I run out of tests. I can use a 15 cent LH test and get the period prediction aspect (LH is my most steady indicator).

The DOT app tends to give me a risky cycle whenever I ovulate late and have a shorter luteal phase. I do not rely on this for pregnancy prevention. Overall though, DOT has not given me many risky ways. I use it for long-term period prediction, and it is the most accurate period predictor I’ve ever used for planning months in advance.

What to Consider Before Switching Methods

1. Why are you unsatisfied with your current method? Is it the amount of safe days, or is it the routine that you don’t like?

2. Do you have medical needs that could be addressed by another method?

Sometimes the grass isn’t greener on the other side, but if you are like me and can’t have period sex or don’t want to have period sex, methods like Billings without calculation rules will almost always include more safe days if you are dedicated enough to learn the method and chart it accurately.

Folks in irregular cycles like in postpartum time or with PCOS may benefit from more flexible methods without calculation rules

*DISCLAIMER: DO NOT TRY TO LEARN FROM MY CHARTS. MY CHARTS ARE NOT YOUR CHARTS.

One Cycle Seven Ways: Experimenting with Marquette (Clearblue Monitor), Billings Method, Sympto-Thermal, Daysy, Kegg, DOT, and more!

Over the last several months, I have been testing multiple femtech products (such as Daysy Fertility Tracker, Kegg, DOT) and comparing them to charting methods like Marquette, Billings Ovulation Method, and Sympto-Thermal (NFPTA). These products and methods rely on different fertility signs such as basal body temperature, cervical mucus, urinary hormones, electrolyte levels, and calendar dates.

Disclaimer: Do not attempt to learn to chart using this post. My own experience may not reflect your unique cycles. My fertility intentions may not be your intentions.

Keep in mind that different methods may change safe days over time. The following data is only a snap shot of what fertility windows for avoiding pregnancy could look like. In particular, the Daysy thermometer only has 4 cycles of data on me.

Expected Consecutive Abstinence Over 3 Cycles

Cycle 52

  • Billings Ovulation Method: 15 (9 consecutive)
  • Marquette: 13
  • Sympto-thermal: 16
  • DOT: 12
  • Daysy: 15

Cycle 53

  • Billings Ovulation Method: 14 (8 consecutive)
  • Marquette: 13
  • Sympto-thermal: 13
  • DOT: 12
  • Daysy: 14

Cycle 54

  • Billings Ovulation Method: 16 (9 consecutive)
  • Marquette: 15
  • Sympto-thermal: 19
  • DOT: 12 (EXTREMELY RISKY)
  • Daysy: 15

From this data, you can see that sometimes the amount of expected abstinence does not differ from method to method, and sometimes it differs a whole lot! On my last cycle with DOT, it ended my avoidance window on the day after peak fertility occured. Fertility is still potentially high on the 3 days following this date.

Billings method almost always had the least consecutive abstinence because it relies on real-time fertility signs to open the window. However, because it rejects calculation rules and relies on one primary sign, only alternative evenings are ever allowed for pre-ovulatory sex. In addition, heavy days of menstruation are not allowed due to the possibility of early ovulation, and the bleeding obscuring the opening of the fertile window.

Other methods like Daysy, Sympto-thermal, DOT, and Marquette do allow pre-ovulatory consecutive sex, but most of that falls during menstruation for my cycle ranges (25 to 30 days).

Whatever method works best for someone is very dependent on their lifestyle and what someone is willing to diligently track.

The Same Chart Seven Ways

The highlighted days represent days to not use in order to avoid pregnancy with these methods.

My hearts are left on to show the fertile window and for authenticity. Do not use these charts to try to learn the rules of any method or to determine when sex is safe. You will see some broken rules based on my own personal intention level and on the fact that not all fertility signs will show the same window.

The Billings Ovulation Method draws the fertile window based on vulva sensation and cervical mucus. Any heavy bleeding is considered potentially fertile because it obscures readings and ovulation can always happen early. It requires alternating evenings for sex during the established basic infertile pattern.
This is the Marquette Method while using only urinary hormones and calculation rules. Fertile window opening determined by calculation rule based on last 6 cycles or first “H” reading on the Clearblue monitor. Clearblue measures estrogen and luteinizing hormone. My first window is also closed by a progesterone test in addition to meeting PPHLL rules.
This is the double-check sympto-thermal method per Natural Family Planning Teachers Association (NFPTA) rules. It opens the fertile window based on the shortest cycle in the last year minus 20. It closes the fertile window based on cervical mucus and basal body temperature.
This is a chart with the Daysy Fertility Tracker. This basal body thermometer learns your patterns over time and opens the fertile window based on past cycle data. The fertile window changes with time, and this is technically my 3rd Daysy cycle. Caution days and Red X days are for avoiding intercourse. Daysy does not allow the user to mark temperatures questionable, but I have marked two days questionable because I drank alcohol or had the heater on.
This example chart includes my cervical mucus notes for more context. DOT is a calendar based method that looks at the last 12 cycles of data. Only people in regular cycles can use DOT. Black moons are days available for intercourse based on the calendar method. In the next line, I also have included Kegg. Kegg predicts ovulation for trying to conceive purposes only, so I am including it as a bonus comparison. By reading the electrolyte levels in my cervical mucus, it determined that these 3 days were the most fertile days of the cycle. A full Kegg review is forthcoming in December 2020.
This is a resting heart rate chart. Resting heart rate has been shown to correlate with the menstrual cycle. I convert my heart rate like this: 69 = 96.9, 70 =97.0, 71 = 97.1, etc to be able to fit it onto the graph. You can see that it very closely followed my ovulatory pattern.
Here is my chart with all the data in one. It is so cool how different fertility signs draw the fertile window!

Unfortunately, my Mira Fertility sticks were flawed, so I had to remove that data from this experiment. In the future, I will do a comparison post also using this device. I am currently still testing the Kegg device, and a review with full Kegg charts is forthcoming in December. Kegg cannot be converted to display on the Read Your Body app, so I could only include the fertile days in this post.

Do you have any questions about all of these methods?

Consider coming to my free Instagram Live on femtech on November 28th. You can find me @chartyourfertility.

On December 12th, I’m offering a “pay what you can” introduction session that is minimum $5 to $30 USD on regular FABM methods and what the main differences are. Reach out to me if you would like to come.

Finally, a special shout to the Body Literacy Collective and the Read Your Body app for making this post possible by creating the most versatile charting app on the market!

Why You Should Be Cautious About Calendar-Based Methods (Daysy, Natural Cycles, DOT)

Calendar methods get a really bad rap in the fertility awareness communities. A lot of this is for a very good reason. When the calendar rhythm method was discovered in the 1930s, it was revolutionary. However, since then, we have discovered real-time fertility signs such as cervical mucus, basal body temperature, and urinary testing.

To illustrate why calendar-based rules can be both risky and occasionally line up with real-time signs, I charted with three calendar-based methods for opening the fertile window versus a method with real-time fertility signs only (specifically I used the Billings Ovulation method for my real-time method).

In the first line, you will see the Natural Cycles method. This method relies on basal body temperature as its only required real-time sign. Unfortunately, basal body temperature can only tell you when your fertile window closes, not when it opens. Temperature has no predictive qualities for letting you know if you are going to ovulate at a different time than normal.**

With only 3 cycles of my previous data, Natural Cycles gave me until day 8 as safe for this cycle. What Natural Cycles doesn’t know is that my cycles range from 24 to 30 days long over a calendar year. For this reason, it can be quite risky some cycles for me to be allowed safe sex until day 8. The fact that this cycle happened to line up is merely a coincidence! This coincidence can cause a confirmation bias when people use this app and do not get pregnant. If you are seriously avoiding, be wary of any method that doesn’t allow you to crosscheck the opening of your fertile window.

Natural Cycle also closed my fertile window in an incredibly risky manner. It told me I was safe on the morning after my real-time sign of “peak” day. In fertility awareness based methods, “peak” is the highest level of fertility you can get in a cycle. The two days following Peak day also have a significant chance of ovulation occurring. Every time I have used Natural Cycles (here is my previous try with it last year), it gives me a very risky closing to the fertile window.

Here is my full chart from Natural Cycles this time:

Natural Cycles app

Next up on the chart above illustrating my safe days is the Daysy thermometer. Daysy is a thermometer that relies on calendar based rules and potentially earliest temperature shift based rules to open the fertile window. In my two experiences with Daysy, it has been much more conservative than Natural Cycles. Daysy does learn over time, so it is possible I could have a risky day with it in the future, but so far I have not had any risky days with Daysy.

You can see in the image above that Daysy confirmed ovulation last out of all of the methods. I believe this is because my temperature shift was a bit erratic and because the device does not allow the user to mark temperatures questionable (I had two that were marked questionable for my own manual interpretation).

Daysy does not rely on anything except cycle length and temperature shift timing to open the fertile window. For this reason, Daysy can be risky if you ever have a very early ovulation. It can also be risky if the user is not careful about only taking their temperature when it is not disturbed, or if the device misreads a temperature shift. In my experience, Daysy tends to be much more cautious than Natural Cycles.

Daysy Chart

My third line is a true calendar only method. DOT has over a year of my data; however, the prediction has only given me one extra safe day during my whole use of the app. DOT is entirely based on the calendar method. However, interestingly DOT got higher efficacy than Natural Cycles in their study. Here is my DOT chart below

While I do not recommend the calendar method to most charters, this app can be useful for period prediction or for birth control if you are okay with an unintended pregnancy if you were to suddenly have a longer or shorter cycle. Users for DOT must have no more than 8 days variation in their cycle per calendar year.

In the example above, DOT actually gave me no risky days whatsoever. Again, this is a coincidence that it seemingly lined up with other signs. At any time, cycles can always change.

DOT the app

Finally, my main method is the Billings Ovulation Method. Billings relies only on real-time fertility signs. This means that they reject any calendar-based thinking, including the idea that menstruation is automatically safe. My Billings chart was based on when cervical mucus opened the fertile window (cervical mucus is what helps sperm survive) and when cervical mucus peak rules closed the window (when sperm can no longer access the cervix because ovulation is over and the cervical mucus plug has closed).

I always recommend real-time fertility signs to anyone who wants very high efficacy, the least amount of consecutive abstinence, who may be in regular or irregular cycles, and who want to understand their body and their health on a more deeper level. Here is an example of a Billings method chart. The babies represent possibly fertile days.

Conclusion:

I hope this post helps you think critically about whether calendar-based methods for opening the fertile window are right for you!

Here is a breakdown of efficacy for these methods:

Daysy: Claims 99.4% perfect use, but their study was retracted.

Natural Cycles: 98% perfect use, 93% typical use.

DOT app: 99% perfect use, 95% typical use.

Billings Method: 97.8 to 100% perfect use, typical use varies depending on country.

**Some modern fertility awareness methods use the Doering Rule to set the opening of the fertile window. This can be very safe and yield high efficacy. Doering is based on the earliest temperature shift of all time (not just the last year).