Diastolic blood pressure: What does the lower number mean?
The diastolic blood pressure is the lower value of a blood pressure measurement.
So with a blood pressure reading of 120/80 mmHg, 80 is the diastolic value.
It shows the pressure in the arteries while the heart relaxes between two beats and fills again with blood.
In short:
Diastolic blood pressure is the lower blood pressure value. Repeated readings from around 90 mmHg are considered elevated. Values around or above 100 mmHg should be checked by a doctor, especially if they occur repeatedly or if symptoms develop.
Diastolic blood pressure is the lower blood pressure value. Repeated readings from around 90 mmHg are considered elevated. Values around or above 100 mmHg should be checked by a doctor, especially if they occur repeatedly or if symptoms develop.
What is diastolic blood pressure?
The heart works in two phases: When the left chamber contracts, it pumps blood into the body.
This creates the systolic blood pressure, meaning the upper value.
After that, the heart muscle relaxes. The heart chambers fill again with blood coming from the atria.
This relaxation phase is called diastole.
Diastolic blood pressure is the lowest pressure in the circulatory system before the next heartbeat.
That is why it is also called the lower blood pressure reading.
The diastolic value depends, among other things, on the resistance in the blood vessels, the elasticity of the arteries,
the volume of blood, the heart rhythm, and the conditions during the measurement.
Diastolic blood pressure: Table to help you classify it
The following table provides a general classification for adults. What matters is always the average of several correctly measured values.
If the systolic and diastolic readings fall into different categories, the blood pressure is usually classified according to the higher-risk category.
| Category | Systolic | Diastolic |
|---|---|---|
| Optimal | below 120 mmHg | below 80 mmHg |
| Normal | 120–129 mmHg | 80–84 mmHg |
| High-normal | 130–139 mmHg | 85–89 mmHg |
| High blood pressure, Grade 1 | 140–159 mmHg | 90–99 mmHg |
| High blood pressure, Grade 2 | 160–179 mmHg | 100–109 mmHg |
| High blood pressure, Grade 3 | 180 mmHg or higher | 110 mmHg or higher |
You can find the full overview in our
blood pressure values table.
When is the diastolic value too high?
A diastolic value is considered elevated when it repeatedly falls in the range of
90 mmHg or higher. Individual elevated readings can be caused by stress, physical exertion, pain, caffeine, nicotine,
excitement, or an incorrect measurement.
So it is not one single measurement that matters, but the pattern of several readings:
If the lower value stays elevated on different days and while you are at rest, it should be checked by a doctor.
Diastolic value over 100: What does that mean?
A repeatedly measured diastolic value around or above 100 mmHg is clearly elevated.
It is no longer just in the high-normal range, but in the range of high blood pressure that needs treatment.
This is especially true if the upper value is also elevated or if there are other risk factors.
If diastolic values are repeatedly above 100 mmHg:
Measure again correctly, document the readings, and make a doctor's appointment promptly. If the values are very high or you have symptoms such as chest pain, shortness of breath, paralysis, speech problems, vision problems, or severe headaches, seek medical help immediately.
Measure again correctly, document the readings, and make a doctor's appointment promptly. If the values are very high or you have symptoms such as chest pain, shortness of breath, paralysis, speech problems, vision problems, or severe headaches, seek medical help immediately.
Can only the lower blood pressure reading be too high?
Yes. It can happen that the diastolic value in particular is elevated, while the systolic value
does not yet appear to be significantly elevated. This is often referred to as an isolated or predominantly
diastolic elevation in blood pressure.
An elevated lower value should also not be ignored. It can indicate greater strain on the blood vessels.
The diastolic value can play an important role, especially in younger adults.
Why is diastolic blood pressure important?
Diastolic blood pressure represents the baseline pressure that the blood vessels are exposed to continuously.
It is also important for supplying the coronary arteries with blood.
During systole, the heart muscle contracts. In this phase, blood is pumped at high pressure into the
body's main artery. During diastole, the heart muscle relaxes, the chambers of the heart fill with blood again,
and blood flow to the coronary arteries improves.
That is why persistently high diastolic values can indicate significant strain on the vascular system.
However, your personal risk depends not only on the diastolic value, but also on
systolic blood pressure, age, pre-existing conditions, cholesterol, smoking, diabetes, and other risk factors.
Possible causes of high diastolic blood pressure
An elevated diastolic blood pressure can have different causes. Often, several factors work together.
- Overweight
- Lack of exercise
- Diet high in salt
- Stress and lack of sleep
- Alcohol or nicotine
- Family tendency
- Kidney diseases
- Hormonal causes
- Certain medications
- Sleep apnea
The exact cause cannot be determined from the measured value alone. If the lower value is repeatedly elevated,
the medical assessment should also consider possible associated and underlying conditions.
What symptoms can an elevated diastolic blood pressure cause?
High diastolic blood pressure often causes no clear symptoms. Many people notice it
only when their blood pressure is measured. Possible but nonspecific symptoms include:
- Headaches
- Dizziness
- Tinnitus
- An inner sense of restlessness
- Sleep problems
- Heart palpitations
- Shortness of breath
- Vision problems
These symptoms can have many other causes. High blood pressure can only be diagnosed reliably by
measuring correctly.
More about this:
High blood pressure: Symptoms and warning signs.
What matters more: systolic or diastolic?
Both readings are important. The systolic value shows the pressure when blood is pumped out of the heart.
The diastolic value shows the pressure during the relaxation phase.
In many older people, the systolic value rises mainly, while the diastolic value can be normal
or even lower. In younger people, however, an increase in the lower value can also play an important role.
We explain the difference in more detail here:
Systolic blood pressure.
Diastolic blood pressure and pulse pressure
From systolic and diastolic blood pressure, you can calculate the
pulse pressure.
It is the difference between the upper and lower value.
Example:
- Blood pressure: 140/90 mmHg
- Pulse pressure: 140 minus 90 = 50 mmHg
A noticeably high or low pulse pressure can provide additional clues, but it does not replace a medical evaluation.
What should you do if the diastolic value is too high?
- Sit down calmly and wait a few minutes.
- Measure again under correct conditions.
- Write down the systolic value, diastolic value, pulse, time, and any special circumstances.
- Repeat the measurement on several days.
- Discuss repeatedly elevated values with your doctor.
Do not change or stop taking blood pressure medication on your own. Dietary supplements
or over-the-counter medicines should also not be taken indiscriminately if you have high blood pressure.
Measure correctly: how to make the lower value more comparable
Measurement errors can distort the diastolic value. Therefore, make sure the measurement conditions are as consistent as possible.
- Before measuring, sit quietly for a few minutes.
- Support your arm at heart level.
- Use an appropriate cuff size.
- Don't talk during the measurement.
- Don't measure right after exercise, coffee, nicotine, or when you're upset.
- For comparison measurements, try to measure at the same time of day.
More about this:
How to measure blood pressure correctly.
Document blood pressure readings
If diastolic blood pressure is repeatedly elevated, regular documentation can help.
With Tensana, you can record systolic value, diastolic value, pulse, medication, and
notes, and review them for your doctor's appointment.
Frequently asked questions about diastolic blood pressure
What does the diastolic value mean?
The diastolic value is the lower blood pressure reading. It shows the pressure in the arteries,
while the heart relaxes between two beats.
Is a diastolic value of 90 too high?
A single reading of 90 mmHg does not necessarily mean you have a diagnosis. But if the diastolic value
is repeatedly 90 mmHg or higher, it is considered elevated and should be checked.
What does a diastolic value over 100 mean?
Repeated diastolic values around or above 100 mmHg are clearly elevated.
They should be discussed with a doctor soon.
Can the lower value be high even if the upper value is normal?
Yes. That can happen. Even then, the value should be taken seriously and checked by a doctor
if it occurs repeatedly.
Why does diastolic blood pressure fluctuate?
Blood pressure fluctuates naturally. Stress, movement, sleep, the time of measurement, caffeine, nicotine,
medication, and measurement errors can affect the diastolic value.
What's the difference between diastolic and systolic?
Systolic is the upper value when the heart contracts. Diastolic is the lower value
during the heart's relaxation phase.
Sources:
This article is from Tensana – the leading app since 2011, helping hundreds of thousands of people monitor their blood pressure every day.
Our content is based on carefully researched, evidence-based data and is continuously updated (as of 05/2026).
Author Horst Klier has been closely involved with high blood pressure since 2002 – initially because he was personally affected and, since 2009, as the developer of Tensana – and is now regarded as a recognized blood pressure expert thanks to his app and specialist platform, used millions of times, as well as his numerous publications. As the author of several health guides and specialist articles, he communicates complex knowledge in a clear and practical way.
Author Horst Klier has been closely involved with high blood pressure since 2002 – initially because he was personally affected and, since 2009, as the developer of Tensana – and is now regarded as a recognized blood pressure expert thanks to his app and specialist platform, used millions of times, as well as his numerous publications. As the author of several health guides and specialist articles, he communicates complex knowledge in a clear and practical way.
