Product Review: Daysy Fertility Monitor

Hey guys,

It's been a minute! This post is a follow up to my Hormone Imbalance Part 1 and Part 2 posts. To summarize, my transition away from hormonal birth control had a hugely positive impact on my health but left me wanting a better, safer anti-baby alternative.

I read a lot about the Fertility Awareness Method (tracking basal body temps to predict fertile/non-fertile windows) but wasn't keen on the idea of recording and graphing these things daily (ain't nobody got time for that). That's when I came across the Daysy Fertility Monitor - it measures your basal temp every morning, tracks it and learns your cycle to predict fertile and non-fertile days with 99.3% accuracy - all without chemicals, hormones, side-effects, etc. just science. I reached out to the company and they so kindly shipped me a device to check out! 

DISCLAIMER: Daysy provided this device for free in exchange for writing a review; however, all views are my own. Also, the links to Daysy on this post are affiliate links, meaning if you purchase the device through that link you will get a discount and are helping to support kaelyRD as well. win/win :) 

How your basal temp predicts fertility:

During the first 2 weeks of your cycle, called the follicular phase (starting day 1 of your period) your body temps are lowest as progesterone levels are very low and estrogen levels are higher. When ovulation occurs, you see a noticeable spike in temperature as progesterone levels rise. High progesterone and relatively lower estrogen keep temperatures higher for the second two weeks (luteal phase) until the next period starts. By knowing your temperature, and the unique trends that your body follows each month, Daysy is able to predict when you are fertile and when you are not.  

Learn even more by connecting with Daysy View on your phone:

If all you care about is whether or not you are within your fertile window, you can just stop here. But you do have the option to plug daysy into your phone and see the graphs of your body temp. This is where I nerd OUT because there is so much to learn here! Basal body temps give you insight into thyroid function, exercise recovery, sleep quality and hormone levels. When I first started using Daysy, I thought there was something wrong with the device or the way I was using it because my body temps were very low and I never had a clearly defined ovulatory temperature spike. Now that I have been tracking for a few months it is clear that I am STILL dealing with some low progesterone issues (ugh) and that is the reason for low temps and lack of a clear post ovulation spike. In the 2 years since coming off the pill I have made a lot of progress in this department but was sad to see it is not completely resolved yet. The silver lining here is that at least I know and I can get back to work on boosting my progesterone (I plan to go back to using Vitex (chaste tree) for a few months, B6 and buckling down on stress management again - I'll let you know how it goes). 


  • easy to use - simply a sublingual temp taken first thing in the morning

  • easy to read - red (fertile), yellow (learning) and green (infertile) lighting makes it simple

  • 99.3% accuracy once Daysy "knows" you and your patterns

  • you can nerd out by looking at the details on the smartphone app! This can teach out about how regular your ovulation is and give you an idea of how healthy your sex hormone and thyroid levels are

  • gives you the confidence of knowing exactly where you are in your cycle which has applications for fertility (obviously) as well as diet and exercise strategies (more on that later)


  • it takes about 3 months for Daysy to "know" you, so you've gotta be patient to reap the rewards

  • it is best to take your temperature right after you wake up, so if you are prone to snoozing your alarm and lingering in a half-sleep phase for a while before "actually" waking up and taking your temp this can be challenging (though you could consider it a "pro" as a push toward getting you up on time ;))


I love this device and the knowledge and control it gives me. I highly recommend it for anyone looking for a non-hormonal (but effective) form of birth control! If you are interested check them out and get your discount by clicking the image on the right or enter DaysyUS+44 at checkout


Thanks for reading, let me know if you have any questions!


xoxo Kaely

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