Why You Should Track Your Cycle (and What Causes Irregular Periods)

Most people track their period for one reason: so it does not surprise them. That is useful, but it undersells what the cycle actually is. Your menstrual cycle is one of the clearest monthly readouts you get on your overall health, and the medical world treats it that way. The American College of Obstetricians and Gynecologists formally recommends using the menstrual cycle as a vital sign, in the same category as heart rate and blood pressure, because changes in it often show up before anything else does (ACOG Committee Opinion No. 651, 2015, PMID: 26595586).

That is the case for tracking. Not because an app tells you to, but because a cycle you have documented is a cycle a practitioner can actually work with. Here is what to record, what counts as normal, and the six most common reasons cycles go irregular.

Why tracking is worth the two minutes a month

Know your normal. Cycle length, flow, and symptoms vary a lot between people. There is no way to know that your cycle has changed unless you know what your baseline was. Tracking three or four cycles gives you that baseline.

Understand why you feel different across the month. Hormones shift across each phase, and so do your sleep, focus, appetite, and energy. When you can see the pattern, you can plan with your body instead of being confused by it.

Catch changes early. Skipped periods, a suddenly heavier flow, or new pain are often the first signal that something needs attention. These changes are easy to dismiss in the moment and obvious in a log.

It reflects your overall health. A cycle that arrives predictably is a sign that a whole chain of signalling, from the brain to the ovaries, is working. When that chain gets disrupted by stress, illness, or under-fuelling, the cycle is often the first thing to go.

What to actually track

You do not need a complicated system. An app or the notes on your phone both work. What matters is that you capture the same things each month:

• Length of your cycle, counted from the first day of one period to the first day of the next
• Flow intensity, and whether it changed from your usual
• Cramps and pain, including where it sits and how long it lasts
• Mood and energy shifts across the month
• Sleep quality
• Skin and digestion changes, which often move with the cycle

Track for at least three cycles before drawing conclusions. One unusual month is common. A pattern across three is information.

What counts as a normal cycle?

For most adults, a typical cycle runs about 21 to 35 days from the first day of one period to the first day of the next, with bleeding lasting up to roughly seven days. Cycles are considered irregular when they fall outside that window, when the length varies by more than about a week from cycle to cycle, or when periods are skipped altogether.

The more useful definition, though, is personal. A meaningful change from your own baseline matters even if the numbers technically stay inside the normal range. That is exactly why tracking is worth doing.

What causes irregular periods

1. Stress

Ovulation is one of the first things the body sets aside when it perceives a threat. Chronic stress raises cortisol and disrupts the brain signalling that triggers ovulation, which can delay a period or pause it entirely. When stress, weight loss, or heavy exercise shut down the cycle this way, it is called functional hypothalamic amenorrhea, and the Endocrine Society treats it as a recognized clinical condition rather than a quirk (Gordon et al., 2017, PMID: 28368518).

2. Over-training

Hard training is not the problem on its own. Hard training without enough recovery and enough food is. When exercise load outpaces fuel intake, the body reads it as scarcity and deprioritizes reproduction, which can stop ovulation (Gordon et al., 2017, PMID: 28368518). This shows up most often in endurance, aesthetic, and weight-class sports.

3. Under-eating

This is the same mechanism from the other direction. When energy intake is too low for what your body is doing, a state researchers call low energy availability, hormonal signalling gets disrupted and menstrual irregularity is one of the earliest consequences, alongside effects on bone density and immunity (Vardardottir et al., 2020, PMID: 32902400). Missing periods is not a sign of discipline. It is a sign of a deficit.

4. Hormone imbalances

Two are especially common and both are treatable. The first is PMOS, the condition renamed from PCOS in 2026, where the cycle becomes irregular because ovulation happens infrequently or not at all. Women with the anovulatory pattern tend to have longer cycles or absent periods along with higher androgens (Burgers et al., 2010, PMID: 20843954).

The second is thyroid dysfunction, which is easy to miss because the symptoms are vague. In one study of women presenting with menstrual disorders, 44 percent had some form of thyroid dysfunction, most commonly an underactive thyroid (Ajmani et al., 2016, PMID: 27046965). That is a striking number, and it is a simple blood test.

5. Poor sleep

The hormones that time your cycle run on a circadian schedule, so disrupted sleep disrupts the timing. Sleep loss can blunt the hormonal surge that triggers ovulation, and shift workers show notably higher rates of menstrual irregularity than the general population (Shechter and Boivin, 2010, PMID: 20145718). If your schedule rotates, this is worth factoring in before assuming something is wrong.

6. Medication changes

Starting or stopping hormonal birth control, and some other medications, can unsettle the cycle while your body recalibrates. The reassuring part is that it usually does not take long: in a systematic review, more than 90 percent of people had resumed ovulating within about two cycles of stopping contraception, and most conceived within a year when trying (Girum and Wasie, 2018, PMID: 30062044). If your cycle has not returned after several months, that is worth investigating rather than waiting out.

When to get it looked at

Tracking tells you that something changed. It does not tell you why. The most accurate way to find the cause of an irregular cycle is testing, because stress, thyroid issues, PMOS, and low energy availability can all look similar from the outside and are managed very differently.

A useful starting panel usually includes thyroid function, relevant sex hormones timed to your cycle, markers of blood sugar and insulin if the PMOS picture fits, plus iron and vitamin D. A Naturopathic Doctor can interpret those together with your tracking log, which is far more informative than either one alone. Bring your log to the appointment. It shortens the process considerably.

For related reading, see our pieces on <a href="/blog/signs-of-hormonal-imbalance-pmos-naturopathic-doctor">the signs of a hormonal imbalance</a>, <a href="/blog/pcos-isnt-a-period-problem-naturopathic-doctor">why PMOS is not just a period problem</a>, and <a href="/blog/cortisol-stress-hormone-what-your-body-is-telling-you">what your cortisol is telling you</a>.

Your cycle is information, and it is free. Tracking it for a few months costs almost nothing and gives you and your practitioner something concrete to work from. If your cycle has changed and you want to know why, a licensed Naturopathic Doctor can test for the cause and build a plan around what they find. You can start with a free discovery call. Ontario residents only.