Blood Pressure

What Blood Pressure Measures

Every heartbeat pushes blood through the arteries, and the artery walls push back. Systolic pressure is that push at its peak, the moment the heart contracts and forces blood out. Diastolic pressure is the lowest point, the brief window between beats when the heart relaxes and refills. Together the two numbers describe how hard the heart is working and how much resistance it's working against.^[1]

How It's Measured

The classic method uses an inflatable cuff and a stethoscope. The cuff squeezes the upper arm past the point where blood can flow, then slowly releases. As blood starts moving again, it makes tapping sounds called Korotkoff sounds. The first tap marks systolic pressure, and the point where the sounds disappear marks diastolic pressure. Automated cuffs, including most home and connected devices, skip the stethoscope and instead detect the tiny vibrations the artery wall makes as the cuff deflates, then calculate the two numbers from that pattern.^[1] Newer cuffless devices, like some smartwatches and rings, estimate blood pressure without a cuff at all. A 2025 American Heart Association statement found these devices haven't yet been proven accurate enough to guide a diagnosis.^[5]

Why People Track Blood Pressure

Blood pressure is one of the standard vital signs, checked at nearly every medical visit because it reflects how the heart and blood vessels are working together. Some people track it more often at home simply to see how it moves over time, alongside other biometrics.

Whether it shifts with the menstrual cycle is a genuinely open question. One early study found blood pressure ran a bit higher at the start of menstruation and lower in the back half of the cycle.^[2] A separate study that used 24-hour ambulatory monitoring, a more continuous measurement than a single cuff reading, found no significant change across cycle phases at all.^[3] Studies disagree here, and that disagreement is itself the finding: blood pressure has plenty of day-to-day variability from sleep, stress, activity, and posture that isn't tied to cycle phase, and that noise can be larger than any pattern researchers are trying to isolate.^[4]

How Go Go Gaia Tracks Blood Pressure

Go Go Gaia pulls blood pressure readings from Apple HealthKit, so a reading from a connected cuff like an Omron or Withings device syncs in automatically. You can also log a reading by hand if your cuff isn't connected. Either way, the app charts systolic and diastolic numbers as a trend next to your cycle phase and other biometrics, instead of leaving each reading as an isolated data point.

What the Research Shows

A 1991 study in Clinical Science tracked blood pressure across the menstrual cycle and found it was higher around the onset of menstruation than during most other phases, with lower readings in the days spanning roughly day 17 to day 26.^[2]

A 1996 study using 24-hour ambulatory monitoring, comparing women with normal ovulatory cycles to women on oral contraceptives, found blood pressure did not change significantly across the cycle in either group.^[3] The two findings sit in real tension, which is common in this kind of research: small sample sizes, different measurement methods, and normal individual variability all make a genuine cycle-phase effect, if one exists, hard to isolate from the noise.^[4]

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

What's the difference between systolic and diastolic blood pressure?

Systolic pressure is the peak force in your arteries as your heart contracts and pushes blood out. Diastolic pressure is the lowest force, measured in the moment between beats when the heart relaxes and refills. Both are recorded in millimeters of mercury (mmHg) and written as systolic over diastolic.

Is a wearable's blood pressure reading as accurate as a cuff?

Cuffless devices like smartwatches, rings, and patches estimate blood pressure without inflating around a limb, and a 2025 American Heart Association scientific statement found they haven't been proven accurate or reliable enough to guide diagnosis or treatment. Devices that use an actual inflatable cuff, whether a manual sphygmomanometer or an automated connected cuff, use established measurement methods.

Does blood pressure change across the menstrual cycle?

The research is genuinely mixed. Some studies find blood pressure runs a bit higher around the start of menstruation and lower in the mid-to-late cycle. Others, including one using 24-hour ambulatory monitoring, find no significant change across cycle phases at all. Day-to-day variability from other factors is a normal part of how blood pressure behaves in anyone.