Probably not much. In the few studies that have looked, the combined pill did not lower heart rate variability (HRV), and it may flatten the monthly rise and fall seen in natural cycles. In 17 healthy pill users measured during their active-pill and pill-free weeks, no HRV measure differed between the two (Teixeira and colleagues, 2015).
What the studies found
The natural cycle has a known pattern. HRV tends to be higher in the first half and lower after ovulation, when progesterone rises, and a meta-analysis of 37 studies found the drop from the first half to the second (Schmalenberger and colleagues, 2019). Within one person, higher-than-usual progesterone goes with lower-than-usual HRV (Schmalenberger and colleagues, 2020). The page on HRV and the menstrual cycle covers this phase by phase.
Combined pills replace that rise and fall with a steady dose of synthetic hormones, so the question is whether the swing disappears and whether HRV sits lower overall.
- On and off the pill, same person. The Brazilian study recorded a 20-minute ECG ECG A recording of the heart's electrical activity, taken with electrodes on the skin. ECG-based RR intervals are the reference standard for measuring HRV. More about ECG in 17 women aged 19 to 31 who had used the pill for at least six months, once in the pill-free week and once during active pills. Estradiol and progesterone were similar at both visits. HRV, resting heart rate Resting heart rate How many times your heart beats per minute while you are fully at rest. For adults it is usually 60 to 100 beats per minute, and lower in well-trained athletes. More about Resting heart rate and blood pressure did not differ between the two phases (Teixeira and colleagues, 2015).
- Pill users against natural cycles. A 2023 US study compared 22 young women, some naturally cycling and some on the pill, in the early follicular and early luteal phases. Most vagal measures did not differ between phases or groups. One measure, pNN50 pNN50 The percentage of neighbouring NN intervals that differ by more than 50 milliseconds. It tracks fast, vagally driven changes, like RMSSD, but as a share rather than a size. More about pNN50 , was higher in pill users during their placebo week, and the authors concluded the pill does not appear to harm vagal control in young, healthy women (Blake and colleagues, 2023).
- The review. A 2016 review of 45 studies on hormones and HRV across a woman’s life found that the intake of oral contraceptives appeared not to alter the vagal modulation of the heart (von Holzen and colleagues, 2016).
The limits are clear. These are small studies of young, healthy women on combined pills, measured once or twice. None of these studies covered progestin-only pills, hormonal IUDs, implants or injections, and none followed HRV across months of starting or stopping contraception.
How to read your own data
- Expect a flatter month. If your cycle used to show a dip before your period and now does not, that matches the research. It is not a sign of poorer recovery.
- Tag the change. When you start, stop or switch contraception, note the date in your app and compare from that point on. The lesson on building your HRV baseline shows how.
- Give it time. After stopping, the natural pattern may return. Compare the same phase across two or three cycles before drawing conclusions.
- Watch heart rate and temperature too. On the pill, the small rise in overnight heart rate and temperature after ovulation may be absent as well.
If your readings seem to move a lot for other reasons, see why your HRV changes so much. For what happens to HRV later in life, read HRV in perimenopause and menopause.
When to talk to a doctor
HRV cannot tell you whether a contraceptive suits you, and this page is not medical advice. Never start, stop or switch contraception because of a wearable reading. Talk to a doctor about any new symptom after starting a hormonal method, including chest pain, breathlessness, severe headaches, leg swelling or pain, or a racing heart, whatever your HRV shows.