Diastolic pressure is the pressure remaining in the arteries between heartbeats, while the heart relaxes and refills, and it is the lower of the two numbers in a blood pressure reading. In a reading of 118/76 mmHg, the diastolic pressure is 76. It reflects how much resistance the small arteries hold against the flow and how well the large arteries store and release each beat. It is also the pressure that keeps blood moving through the coronary arteries, which fill mainly during diastole.
What it measures
A cuff on the upper arm inflates until it stops flow in the brachial artery, then deflates. Listening with a stethoscope, a clinician records diastolic pressure at the point where the tapping sounds disappear. Home and clinic monitors are oscillometric instead: they read the pattern of oscillations in the cuff and estimate both numbers from it, so a validated device matters. The paired upper number, Systolic pressure (upper), comes from the same deflation.
Physiologically, it is driven by the tone of the small peripheral arteries, by heart rate (a slow heart spends longer in diastole, so pressure falls further), and by the elasticity of the aorta. The difference between the two numbers is Pulse pressure, which widens when the large arteries stiffen. Technique moves the number: sit quietly for about five minutes, feet flat, cuff at heart level and correctly sized, and average two or three readings.
Typical values
US guidelines from the American College of Cardiology and American Heart Association classify office diastolic readings in adults as follows.
| Category | Diastolic (mmHg) |
|---|---|
| Normal | below 80 |
| Hypertension, stage 1 | 80-89 |
| Hypertension, stage 2 | 90 or higher |
The thresholds are not universal. European guidelines keep 90 mmHg as the diastolic level that defines hypertension and treat the band just below it as high-normal, so the same reading can be labeled differently on either side of the Atlantic. Home and 24-hour ambulatory averages use lower cut-offs than office readings, because they exclude the rise many people show in a clinic. A diastolic under about 60 mmHg is usually noted in older or treated adults, and the full classification is set out in Diastolic pressure (lower).
Why it matters for longevity
Diastolic pressure carries most of its predictive weight early in life. In long-running cohort studies, it rises through early and middle adulthood, then plateaus and often falls after roughly the sixth decade as the aorta stiffens, which is why raised systolic with a normal or low diastolic becomes the common pattern in older adults. In younger adults, a high diastolic is the more informative signal and is associated with later cardiovascular events.
A low diastolic is not automatically reassuring. Observational data link very low diastolic pressure, particularly in people whose systolic stays high, with more cardiovascular events, plausibly because coronary filling depends on it; whether lowering treatment causes that association or simply marks stiff arteries and frailty is still debated. Trials of blood pressure lowering report benefits for the reading as a whole, so diastolic is best read as one half of a pair, not a target of its own.
What changes it
The levers are the ones that move blood pressure generally, and they work well on diastolic in younger and middle-aged adults, whose pressure is more resistance-driven than stiffness-driven. Losing excess weight lowers it. So does cutting sodium, eating more potassium-rich plants in a DASH-style or Mediterranean pattern, limiting alcohol, and training regularly, with aerobic, isometric and resistance work all showing reductions in trials. Short sleep, untreated sleep apnea and sustained stress push it up. When readings stay high, medication is the main lever, and the choice of class is a clinical decision. What you cannot change: the arterial stiffening of age, which lowers diastolic while raising systolic, family history, and kidney or hormonal conditions that raise pressure secondarily and need diagnosis rather than lifestyle work alone.
Related reading
- Blood pressure (BP)
- Heart Health: A Prevention Guide for Longevity
- Which Blood Tests Reflect Aging and How to Read Them
- How to Improve Metabolic Health: A Practical Guide
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.