In people with natural menstrual cycles, heart rate variability (HRV) tends to be higher in the first half of the cycle and lower in the second half, after ovulation. The change is linked to progesterone, differs a lot from person to person, and is a normal pattern rather than a sign that something is wrong.
Why HRV changes across the cycle
HRV mostly reflects the parasympathetic Parasympathetic nervous system The "rest and digest" branch of the autonomic nervous system. It slows the heart, mainly through the vagus nerve, and drives most of the beat-to-beat variation in HRV. More about Parasympathetic nervous system system, which slows the heart through the vagus nerve Vagus nerve The main nerve of the parasympathetic nervous system, running from the brainstem to the heart, lungs and gut. Its fast signals to the heart drive most beat-to-beat HRV. More about Vagus nerve and lets the time between beats vary. Researchers often call this cardiac vagal activity Vagal tone The ongoing influence of the vagus nerve on the heart, which slows it down. It is usually estimated from HRV measures such as RMSSD and HF power. More about Vagal tone . Hormones that rise and fall through the cycle seem to shift it.
The clearest link so far is with progesterone, the hormone that rises after ovulation. Two studies by a German and US research team measured hormones and HRV repeatedly in the same people: 40 participants once a week for four weeks, and 50 participants at three phases confirmed by ovulation tests (Schmalenberger and colleagues, 2020). In both, when a person’s progesterone was higher than their own usual level, their HRV tended to be lower than usual. Estradiol, the main form of estrogen, showed no clear effect.
The luteal phase also brings a slightly higher heart rate and body temperature. In a study of 26 healthy women wearing an Oura ring through one full cycle, heart rate and skin temperature during sleep were higher in the mid- and late luteal phase than during the period and around ovulation (Alzueta and colleagues, 2022). RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next. It mainly reflects vagal activity. More about RMSSD tended to be lower in the luteal phase, though that difference was less clear-cut.
Phase by phase
The table summarises the pattern reported across studies. Day counts vary from cycle to cycle and person to person, so the phases are described by what happens rather than by fixed dates.
| Phase | What happens | What studies report for HRV |
|---|---|---|
| Menstrual | Bleeding days at the start of the cycle | Higher than in the premenstrual days |
| Follicular | From the period until ovulation; estradiol rises | Higher than in the luteal phase overall, and higher than in the premenstrual days |
| Ovulation | An egg is released, mid-cycle | Too few studies to say |
| Early to mid luteal | After ovulation; progesterone rises | Lower than other phases in one 2020 study; pooled comparisons unclear |
| Premenstrual (late luteal) | The last days before the next period | Lower than during the period and the late follicular phase |
The largest summary comes from a 2019 meta-analysis of 37 studies with 1,004 participants, all with natural cycles (Schmalenberger and colleagues, 2019). It found a significant drop in cardiac vagal activity from the follicular to the luteal phase. Finer comparisons found bigger drops from the menstrual and mid-to-late follicular phases to the premenstrual days, but each rested on only five to eight studies. The other phase-to-phase comparisons were not statistically clear, and several rested on only two to four studies. In the 2020 study, HRV was lower in the mid-luteal phase, when progesterone is high, than in the other phases measured.
A smaller US study recorded resting ECGs from 13 women at five points in the cycle (Tenan and colleagues, 2014). Heart rate and breathing rate rose across the cycle while HRV fell. After the researchers accounted for the change in breathing, the drop still looked like a pullback of the parasympathetic system.
Go deeper How big is the change?
The meta-analysis reports effect sizes (Cohen’s d), which compare the size of a change with how much values usually vary. Around 0.2 is often called small, 0.5 medium and 0.8 large.
- Follicular to luteal phase: d = −0.39 (37 studies, 1,004 people), a small-to-medium drop.
- Menstrual to premenstrual: d = −1.17 (5 studies, 200 people).
- Mid-to-late follicular to premenstrual: d = −1.32 (8 studies, 280 people).
The last two look large, but their confidence intervals were wide (for example, −0.17 to −2.18 for menstrual to premenstrual), so the true size could be much smaller. These are averages across groups. They cannot tell you how many milliseconds your own RMSSD will move.
How much people differ
Not everyone shows the same pattern, and the evidence has clear limits:
- Individual differences. The 2020 study authors call for research into why some people’s HRV responds more to progesterone than others’.
- Small studies. The single studies described here included between 13 and 50 people, mostly followed for one cycle.
- Natural cycles only. The meta-analysis included only naturally cycling, premenopausal people. These findings say little about hormonal contraception, pregnancy, perimenopause or menopause.
How to read your own data across the cycle
- Log your cycle next to your HRV. Many apps let you tag period days. Without that, a luteal dip can look like a run of bad recovery.
- Compare like with like. Check this week’s HRV against the same phase in your previous cycles, not against the week before. The lesson on building your HRV baseline explains baselines in more detail.
- Give it two or three cycles. One cycle is not enough to see your own pattern.
- Watch heart rate and temperature too. A higher overnight heart rate and skin temperature after ovulation fit the usual pattern.
- Don’t compare yourself to others. Typical ranges for your age are a loose guide at best; see what is normal HRV. Your own trend over months is more useful.
If your HRV seems to move a lot in general, why HRV changes so much covers the other usual causes.
When to talk to a doctor
HRV cannot tell you anything about your hormones or fertility, and it cannot detect cycle problems. Talk to a doctor if your periods become irregular, stop when you are not pregnant, or come with very heavy bleeding, severe pain or bleeding between periods. Also talk to a doctor if premenstrual symptoms such as low mood or anxiety are disrupting your life. Your symptoms are the reason to get checked, whatever your HRV shows.