Diastolic Blood Pressure: What the Bottom Number Means
The bottom number in your blood pressure reading reflects how well your arteries relax between heartbeats. Here is what every range means and why it matters.
What Does Diastolic Blood Pressure Measure?
Between each heartbeat, your heart relaxes and refills with blood. Diastolic blood pressure is the pressure your blood continues to exert on artery walls during this resting phase. It is the lower of the two numbers in a reading like 120/80 mmHg.
Even when your heart is not actively pumping, blood still presses against artery walls due to the elastic recoil of the large arteries. Diastolic pressure reflects how much baseline tension your arteries experience continuously, 24 hours a day.
A high diastolic reading means your arteries are under elevated pressure even at rest, which over time can damage artery walls, strain the heart, and increase the risk of serious cardiovascular events.
Diastolic Blood Pressure Ranges
Based on American Heart Association guidelines.
Why Diastolic Pressure Matters More Than People Think
Many people focus only on their systolic number. But diastolic pressure carries its own distinct set of risks.
It reflects artery health
High diastolic pressure often signals that your arteries are not relaxing fully between beats, which increases the workload on your heart.
Linked to younger-adult risk
While systolic pressure matters more in older adults, elevated diastolic pressure is a stronger risk marker for cardiovascular events in people under 50.
Isolated diastolic hypertension
Some people have a normal systolic but high diastolic. This is less common but still requires monitoring and often treatment.
It changes less day-to-day
Diastolic pressure tends to be more stable than systolic throughout the day, making persistent elevation a more reliable warning sign.
Lifestyle factors matter
Obesity, high sodium intake, excess alcohol, physical inactivity, and smoking all raise diastolic pressure and are modifiable through lifestyle changes.
Low diastolic also has risks
Diastolic pressure below 60 mmHg can reduce blood flow to the coronary arteries, particularly in people with existing heart disease.
See Both Numbers in Context with Cardilog
Cardilog logs your systolic and diastolic readings together, shows how they trend over time, and uses AI to explain what your numbers mean. Whether your diastolic is creeping up or you just want to confirm you are in the healthy range, consistent tracking gives you answers.
Frequently Asked Questions
What is diastolic blood pressure?
Diastolic blood pressure is the bottom number in a blood pressure reading. It measures the pressure in your arteries when your heart is at rest between beats, refilling with blood before the next contraction. In a reading of 120/80 mmHg, 80 is the diastolic pressure.
What is a normal diastolic blood pressure?
A normal diastolic blood pressure is less than 80 mmHg. Readings at 80-89 indicate Stage 1 hypertension, and readings at 90 or above indicate Stage 2 hypertension. Readings consistently below 60 mmHg may indicate low blood pressure (hypotension).
Is high diastolic pressure dangerous?
Yes, persistently high diastolic pressure increases the risk of heart attack, stroke, kidney disease, and heart failure. It puts constant strain on artery walls even when the heart is not actively pumping, preventing the cardiovascular system from fully recovering between beats.
What causes high diastolic blood pressure?
Common causes include obesity, high sodium diet, excessive alcohol consumption, physical inactivity, smoking, chronic stress, kidney disease, and certain medications. In younger adults, high diastolic pressure without high systolic is often related to increased peripheral vascular resistance.
What is the difference between systolic and diastolic blood pressure?
Systolic pressure (top number) measures the force during a heartbeat, when the heart contracts. Diastolic pressure (bottom number) measures the force between heartbeats, when the heart relaxes. Both matter. Together they give a complete picture of cardiovascular health. For adults under 50, elevated diastolic pressure carries higher risk. For adults over 50, elevated systolic pressure is generally the stronger predictor of risk.
Can I lower my diastolic blood pressure without medication?
In many cases, yes. The DASH diet (rich in fruits, vegetables, and low-fat dairy), reducing sodium intake, regular aerobic exercise, limiting alcohol, quitting smoking, and managing body weight can each contribute to meaningful reductions in diastolic pressure. Consistent home monitoring helps you see whether these changes are working.
Related Guides
Medical Disclaimer: This page is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider about your blood pressure readings and any treatment decisions.