I Tracked These Two Simple Biomarkers to Understand My Cycle Better—and It Taught Me So Much More Than I Anticipated

How many times have you turned to a friend and asked, “Why weren’t we taught this at school?” when talking about your health? My guess is: too many to count.

And that’s because, until recently, women’s health had fallen by the wayside in both research and education. In fact, in 2020, only 5% of global research was allocated to women-specific health conditions, with 4% of that focused on cancer alone. Across all clinical trials, only 5% analysed their data separately for men and women, meaning women are often diagnosed and treated based on male biology.

Understandably, that’s resulted in a significant knowledge gap amongst researchers, educators and, ultimately, women ourselves. Depressingly, a survey by Plan UK found that a quarter of 12- to 21-year-olds had spent less than an hour learning about periods at school, whilst a report published this year by femtech company Hertility found that one in four of us don’t know the length of our menstrual cycle.

Even as a health writer, I’ve been in that position. Thanks to years of hormonal imbalances and missing periods, I’d become pretty disconnected from my own body. But as I inch closer to 30 and conversations about PMOS, egg freezing and peri-menopause become more frequent amongst my friends and family, I’ve started to feel uneasy about just how much I still don’t know about my own internal world.

I debated buying a wearable or downloading an app, as many of my friends have. But after a friend introduced me to fertility awareness educator Bethan Walters, who explained that I could gain a better understanding of my cycle manually, using my own biomarkers, I was intrigued. Because, as Hertility’s report shows, although more than 50% of us use apps to track our cycle, many of us don’t have the knowledge to make meaningful use of the data.

So, with Walters’ help, I’ve spent the last month taking a course in my own biology, tracking just two key biomarkers that have given me unprecedented insight into my cycle. For everything I’ve learnt, read on.

And for more support navigating female health conditions, make sure to read our investigations into medical trauma and endometriosis, the shift from PCOS to PMOS and Dr Hazel Wallace’s research findings on the state of women’s menstrual health in the UK. We’ve also got a longevity doctor’s tips for healthy ageing plus expert advice on strength training through menopause from a certified coach.

I Didn’t Realise How Little I Knew About My Cycle –Then I Started Tracking These Two Biomarkers

What is a biomarker?

First things first: what do we mean when we talk about biomarkers? Essentially, it’s any measurable sign or process in the body that helps us understand what’s going on with our health.

The menstrual cycle itself is a key biomarker - often referred to as the fifth vital sign of health, alongside blood pressure, body temperature, heart rate and respiratory rate. “The menstrual cycle is often minimised to a product of our reproductive organs,” says Dr Faye Bate, co-host of the Her Discussions podcast, “but it’s actually a hormonal symphony that falls out of tune when our thyroid, blood sugar, stress levels or nutrition are off.”

She explains that changes to our menstrual cycle can be some of the earliest indicators of underlying health conditions, which is why understanding our own patterns matters for far more than fertility alone. “If our body is not functioning optimally, it shifts its priorities away from baby-making,” says Dr Bate. “By tracking signs of ovulation, you can assess whether your body is playing in tune or whether there’s a disruption that deserves a conversation with your doctor.”

Which biomarkers can be used to track the menstrual cycle?

When it comes to tracking our menstrual cycle, it’s important to realise that what we’re actually trying to follow is ovulation, not menstruation. And that’s because sometimes we can still get a period even when we’re not ovulating. “Someone might still bleed occasionally, giving the impression that everything is fine,” explains Walters. “This is why simply tracking periods isn’t enough.”

When it comes to tracking our menstrual cycle, it’s important to understand that what we’re really trying to identify is ovulation, not menstruation. That’s because ovulation is one of the clearest signs that our hormones are functioning as they should - making it an important marker of overall health, not just fertility. It’s also possible to still experience bleeding without actually ovulating. “Someone might still bleed occasionally, giving the impression that everything is fine,” explains Walters. “This is why simply tracking periods isn’t enough.”

To track ovulation, we can use two key biomarkers: basal body temperature and cervical fluid - each of which reflects changes in a different reproductive hormone. Basal body temperature is driven by progesterone, while cervical fluid is influenced by oestrogen.

“Basal body temperature is the body’s lowest resting temperature, usually recorded first thing in the morning,” says Dr Bate. “It’s typically lower in the follicular phase and rises by around 0.2-0.5°C after ovulation.” This shift, she explains, is driven by progesterone and can be used to indicate that ovulation has occurred.

Cervical fluid, on the other hand, changes in response to oestrogen levels, which is why its texture and appearance shift throughout the menstrual cycle. “Cervical fluid is a mucus-based secretion from the cervix which changes in composition and texture across the cycle to protect the reproductive tract and regulate when sperm can pass towards the egg,” explains Dr Bate.

In a typical cycle, Dr Bate says we tend to see fewer, drier secretions just after menstruation, with fluid becoming wetter, clearer and more slippery as ovulation approaches. “These changes signal the start of your fertile window,” she explains. After ovulation, discharge usually becomes thicker and creamier, which “works to prevent sperm reaching the egg”.

Tracking cervical fluid can also help us spot potential signs of infection, adds Dr Bate. “If your discharge patterns change significantly from what’s normal for you, there’s a strong smell, or it appears yellow or green in colour, speak to your GP.”

What are the benefits of biomarker tracking?

You might be wondering why you’d bother taking your temperature every day or studying the fluid in your knickers when an app or wearable could seemingly do the work for you - especially if you’re not actively trying to get pregnant.

But as we now know, ovulation isn’t just about fertility. “Each time you ovulate, your body produces progesterone, which plays a crucial role in mood, sleep, anxiety regulation, metabolism, bone density and the regulation of the endometrium - aka the inner lining of our uterus,” says Walters. “Ovulation also reflects a healthy rise and fall in oestrogen, which supports cardiovascular health, brain function, skin health and bone density.”

When we aren’t ovulating, it can be a sign that the body is under too much stress. “Stress can come from lifestyle factors, nutritional deficiencies, or underlying hormonal issues,” says Walters. “Whatever the case, tracking ovulation gives you insight into whether your brain, ovaries and hormones are communicating effectively. It’s essentially a monthly check-in on your endocrine health.”

Where manual tracking differs from wearable data is in the immediacy of the information it provides. While many wearables can track temperature changes, they often estimate fertile windows using algorithms and past cycle data, whereas manual methods teach you how to interpret your body’s signals as they happen. “Manual tracking using basal body temperature and cervical fluid is based on observing your body in real time,” explains Walters. “Wearables, on the other hand, tend to rely heavily on temperature trends and algorithms. Some are helpful, but many are still predicting ovulation based on past data rather than identifying what’s happening in the moment.”

By equipping ourselves with this real-time data, says Dr Bate, we’re also better positioned to advocate for our health and seek support sooner when something feels off. “The beauty of the menstrual cycle, unlike most health data, is that we don't need a doctor to access this information. And when we do see a doctor, having that data can potentially help them reach a diagnosis faster, before invasive testing.”

Who is biomarker tracking best for?

Tracking your cycle through biomarkers can be useful for anyone with a uterus, even if you don’t regularly menstruate. “It’s for anyone wanting to gain a deeper understanding of their body’s signals,” says Walters, who encourages those still learning to work with a trained practitioner who can help them interpret what these biomarkers are indicating.

In particular, however, biomarker tracking can be especially useful for those experiencing hormonal imbalances, irregular cycles or conditions such as PMOS, as well as those coming off contraception. “Tracking BBT and cervical mucus offers a way to see whether and when ovulation actually occurs, helps with timing treatments in cases of infertility, and gives clinicians rich, longitudinal data for diagnosis and monitoring,” says Dr Bate.

Of course, for those actively trying to conceive (or, equally, not to conceive), tracking ovulation can also be invaluable. “The ability to recognise the few days leading up to ovulation by tracking cervical mucus can aid in identifying the fertile window (when a woman can get pregnant),” says Dr Bate. “This allows us to optimise the timing of sex for the best chances of conception,” - or, alternatively, to know when to avoid sex or use additional protection to avoid pregnancy.

There’s also a case for biomarker tracking among women who exercise heavily (of which there are an increasing number). “Exercise, nutrition and stress can all affect ovulation and cycle regularity,” says Dr Bate. “Tracking basal body temperature and cervical mucus offers a low-cost way to spot warning signs that you may not be eating enough, are overtraining, or that your body is under too much stress.”

Given how important exercise is for women’s hormonal and overall health, having the tools to spot when we’re pushing too hard is essential. “It could be the difference between exercise being one of the most protective things you do for your long-term health and one of the most damaging,” says Dr Bate, who reminds us that “not ovulating isn’t a perk of being fit - it’s a red flag.”

I Tracked Two Simple Biomarkers for a Month – and It Completely Changed How I Understand My Cycle

Weeks one and two:

Throughout my first month of biomarker tracking, I had weekly lessons with Walters, where she took me through the ways my BBT and cervical fluid could change across the month. She gave me the language to describe the fluctuations I was seeing in fluid texture and colour, and guidance on the degree of temperature change I could expect.

I quickly learned it was important to take my temperature within the same 30-minute window each morning, before eating or drinking. That’s because the fine margins we’re looking at (BBT only changes by around 0.2–0.5°C across the month) are very sensitive to outside influence, with factors like poor sleep or alcohol potentially skewing the results. Walters reassured me this didn’t mean I needed to stop drinking entirely, or feel like I’d failed if I’d slept badly, but that I should note it in case the data looked unusual that day.

I fell into the routine of temperature tracking fairly easily. I kept the thermometer by my bed and took my temperature as soon as I woke, which meant I very rarely missed a day.

Checking my cervical fluid, however, was more challenging. Since I was already aware that some days it appeared whiter and milkier than others, and that volume could vary significantly, I naively assumed I was quite clued up on how it can look throughout the cycle. But as I soon discovered, it’s not only the days when it’s obviously present in your underwear that it requires tracking.

As Walters explained, everyone’s baseline of cervical fluid is different. For some, the baseline is no noticeable fluid, with it only appearing as ovulation approaches. For others, like me, there is always some fluid present, but it increases and changes consistency throughout the cycle. I didn’t just regularly forget to check (you’re meant to do it several times a day), but I also often lacked the language to describe it – whether sticky, stretchy, thin, crumbly or gluey. The changes day to day can be subtle, which means it requires real familiarity with your own patterns to distinguish what’s normal for you.

That, I was told, is largely trial and error, and becomes easier the longer you pay attention - something that I discovered was, in itself, an unexpected challenge. I wouldn’t describe myself as someone shy about investigating my own body, but getting used to touching and examining cervical fluid was definitely unfamiliar territory.

Don’t be put off, though, because once I got used to it, I actually found it empowering and connective. In some ways, it brought me closer to my internal world.

Weeks three and four

By week three, I was still getting to grips with recognising changes in cervical fluid, but I was beginning to see patterns in my temperature chart. Walters had explained that, if I had ovulated, I should see a sustained rise in temperature afterwards. I was also struck by just how much, as she had said, alcohol and sleep affected my readings. On nights when I’d had even two drinks, the following day’s temperature was noticeably higher.

By the end of the month, my cervical fluid tracking was still a little inconsistent, so it was hard to tell whether I had actually ovulated. Walters had explained that when the body is trying to ovulate but not quite succeeding, we can see an ebb and flow of cervical fluid - where it becomes transparent, stretchy or slippery, but never reaches its peak consistency. This felt like it could apply to me based on what I was seeing, but as I’m still getting to grips with consistent tracking and interpretation, I’ll need to continue for a few more months to get a clearer picture.

What I have gained, through Walters’ teaching and daily tracking, is a much deeper appreciation of the complexity of my body, as well as a sense of empowerment from understanding what these signs can reveal about my health. Having never really understood why my cervical fluid changes, and not even knowing that temperature plays a role in ovulation, it feels exciting to finally be equipped with this knowledge.

Even as a purely educational experiment, I’d encourage all women to start becoming more familiar with their cycle. For me, it’s created greater compassion for my body, more confidence when talking about it, and a clearer sense of how I can advocate for myself in medical settings if I ever need to.

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