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.

Top 3 Charting Mistakes When Beginning Fertility Awareness

I’ve been moderating a rather large Facebook group for fertility awareness charters for over a year and a half now (26,000 members and climbing, join here!), and before that I constantly scrolled through the Kindara community charts very regularly. These experiences in various FAM communities, as well as my certification as a FAM instructor, have alerted me to some common mistakes that new charters make. I outline what these are and how to avoid them in this post.

Mistake #1: Using a Fever Thermometer Instead of a Basal Body Thermometer

Many folks read Taking Charge of Your Fertility and see that we only chart to the first decimal place in Fahrenheit. Then they think that using a fever thermometer is okay since fever thermometers have only one decimal place. This is NOT true. We need the sensitivity of a basal body thermometer with two decimal places. If you are someone who has weak temperature shifts, it is even more important to have the right thermometer! Many people also miss that the original studies that the symptothermal efficacy is based on requires you to take your temperature for three minutes. Almost no fever thermometer does this, and even some basal body thermometers do not. Make sure that you have the correct thermometer that allows you to either take your temperature for three minutes or prewarm the thermometer.

Mistake #2: Overmarking or Undermarking Cervical Mucus Observations

I often see people overmark “watery” type mucus because the vagina is always moist. Other people will overmark “creamy” type mucus even though what they are seeing may be cell slough. While it is definitely better to assume fertility if you are uncertain, this can cause unnecessary abstinence. The solution to this problem is to work with an instructor. The efficacy of the method is based on working with an instructor anyways, and it is generally best to get a professional’s advice on your chart if you are seriously avoiding pregnancy. If you need an instructor, you can find one here.

I also see people undermark cervical mucus. This is the more dangerous of the two mistakes. Many people decide not to pay attention to wiping or walking sensation or view sensation as less important than their visible mucus. Since vaginal sensation is equal to cervical mucus, it is highly important that you also chart your sensation according to whatever method you are following. If there is any change in vaginal sensation, even if you do not see mucus, the fertile window should be considered opened in the pre-ovulatory time of the cycle.

Mistake #3: Following a Hodge-Podge of Methods

The fertility awareness method only works as a form of birth control when the rules are followed very carefully according to an established method. Simply beginning to take your temperature and marking mucus without reading a manual or taking a class is NOT enough for anyone who seriously does not want to get pregnancy. Do NOT rely on social media posts to learn how to chart. It is necessary to really learn what you are doing if you do not want an unintended pregnancy. You can find out about multiple methods by visiting my post on getting started.

An Example of a Symptothermal Chart on Kindara