HRV and the Menstrual Cycle: How the Pattern Changes

Heart rate variability (HRV) is common in wearable health data, but cycle phase is often missing from the explanation. If you menstruate, HRV often follows a pattern across the cycle. A reading can be misleading when that context is left out.

What is HRV?

HRV measures the variation in time between consecutive heartbeats. It describes how much the spacing between beats varies rather than how fast the heart beats. Higher HRV generally indicates a well-recovered, adaptable nervous system. Lower HRV suggests that the body is under physical, emotional, or hormonal stress.

Apple Watch measures HRV overnight using the SDNN method (standard deviation of normal-to-normal intervals) and records it as part of your sleep data.

How HRV changes across the cycle

Laboratory and wearable-derived HRV data show a consistent overall pattern:^2,3

Follicular phase (period through ovulation)

• HRV is generally higher
• The parasympathetic (rest-and-digest) branch of the nervous system is more dominant
• Most people feel more recovered and resilient during this phase

Ovulation

• HRV may dip briefly around the ovulation window
• The hormonal surge (LH peak + estrogen peak) creates a temporary shift in autonomic balance

Luteal phase (ovulation through next period)

• HRV trends lower across this phase
• Progesterone increases sympathetic nervous system activity
• Resting heart rate rises by 2–5 bpm on average
• The lowest HRV readings often occur in the 2–3 days before menstruation

Menstruation

• HRV begins to recover once the period starts
• As progesterone falls and the follicular phase begins, parasympathetic tone increases again

Why this matters for interpretation

Comparing a luteal-phase reading with one from the follicular phase can make the later reading look like stress, poor recovery, or illness. A 10–20% swing in HRV across phases can be normal.

Generic HRV apps can therefore be misleading when they do not account for cycle phase. A "below average" reading during the late luteal phase may simply be your baseline for that part of the cycle.

What the research shows

A 2020 study by Shilaih et al. found that wrist-worn devices could detect statistically significant HRV changes between cycle phases. Values were highest in the follicular phase and lowest in the late luteal phase.

Brar et al. (2015) also found that sympathovagal balance shifts toward sympathetic dominance during the luteal phase, consistent with the observed decline in HRV.

Both studies found measurable differences between phases.

How to use HRV data across your cycle

• Compare readings within the same phase. Your follicular-phase HRV is your "rested" baseline, while your luteal-phase HRV is your "loaded" baseline.
• Look for deviations within a phase. If luteal HRV drops more than usual, that may indicate additional stress, illness, or poor recovery.
• Consider wrist temperature, resting heart rate, and sleep quality alongside HRV for a more complete picture.
• Track several cycles. Individual days are noisy, so trends across cycles are more informative.

Reading your own HRV data

HRV is most useful when interpreted in context. For anyone who menstruates, cycle phase is an important part of that context. Comparing your data across several cycles can show whether the expected pattern also appears in your own readings.

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References

1. Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Frontiers in Public Health. 2017;5:258.
2. Brar TK, et al. Effect of different phases of menstrual cycle on heart rate variability. Journal of Clinical and Diagnostic Research. 2015;9(10):CC01-CC04.
3. Shilaih M, et al. Modern fertility awareness methods: wrist wearables capture the changes in temperature associated with the menstrual cycle. Bioscience Reports. 2018;38(6):BSR20171279.
4. Yildirir A, et al. Effects of menstrual cycle on cardiac autonomic innervation as assessed by heart rate variability. Annals of Noninvasive Electrocardiology. 2002;7(1):60-63.