Low Diastolic Blood Pressure: What a Bottom Number Under 60 Means
Low diastolic blood pressure is a bottom number under 60 mmHg. It's often harmless, but with stiff arteries or symptoms it's worth raising with a doctor.
This article is educational content, not medical advice. Always talk to a healthcare professional about your blood pressure.
The thresholds on this page follow the ACC/AHA guideline used in the United States (set in 2017 and kept in the 2025 update), which sets high blood pressure at 130/80 mmHg. Other bodies differ: ESH in Europe and NICE in the UK still define it at 140/90 mmHg. Check the guideline your own clinician uses.
Low diastolic blood pressure means the bottom number of your reading is under 60 mmHg. On its own, with no symptoms, it's often just how your body runs. It deserves a doctor's attention when it comes with dizziness, fainting, chest pain or shortness of breath. The same goes for a low bottom number paired with a high top number, a pattern that often points to stiff arteries.
The US National Heart, Lung, and Blood Institute (NHLBI) sets the edge of low blood pressure at 90/60 mmHg, so a diastolic under 60 counts as low even when the systolic is fine. Under the ACC/AHA categories used by the American Heart Association, a reading below 120/80 is normal, which means a bottom number in the 60s is common and expected.
Mayo Clinic explains that a very low diastolic usually has one of two causes: low blood pressure overall, or stiff arteries from aging, diabetes or fatty buildup (atherosclerosis). In a 2016 study of 11,565 US adults followed for about 21 years, people with a diastolic under 60 had roughly twice the odds of a blood marker of heart-muscle injury compared with those at 80 to 89, and about a 50% higher risk of coronary heart disease.
What counts as a low diastolic reading?
Diastolic pressure is the second, smaller number on the monitor. The NHLBI treats anything below 60 mmHg as low. The bigger question is what the top number is doing at the same time, because the same bottom number can mean different things.
| Example reading | Pattern | What it often points to |
|---|---|---|
| 88/56 mmHg | Both numbers low | General low blood pressure, often harmless if you feel well |
| 112/56 mmHg | Low bottom, normal top | Sometimes called isolated diastolic hypotension; may be your normal, but check the setup |
| 150/55 mmHg | Low bottom, high top | A wide pulse pressure of 95, typical of stiff arteries in older adults |
| Any low reading with dizziness, fainting, chest pain or breathlessness | Symptomatic | Needs a doctor; see the warning section below |
The first row is covered in detail in our guide to what is considered low blood pressure. The rest of this article is about the bottom number specifically.
BPlus color-codes every reading into the same five ranges. Check my readings →
Why does a low bottom number matter?
Your heart muscle gets most of its own blood supply between beats, in the diastolic phase. When diastolic pressure falls very low, less blood may reach the heart muscle itself.
The 2016 analysis of the ARIC study, published in the Journal of the American College of Cardiology, found that a diastolic under 60 was linked to signs of quiet heart-muscle damage and to more coronary heart disease and deaths over the follow-up, though not to more strokes. The links were strongest in people whose systolic was 120 or higher, meaning a wide gap between the two numbers.
A study like this shows an association, not proof that the low number caused the harm. Still, it's why doctors don't treat a low bottom number as automatically good news.
Why is my diastolic pressure low?
Mayo Clinic describes two main routes. The first is low blood pressure overall, which the NHLBI links to causes such as dehydration, blood loss, severe infection and some medicines. In that case both numbers usually drop together.
The second is stiff arteries. Healthy arteries stretch with each heartbeat and spring back, which keeps pressure up between beats. As arteries stiffen with age, diabetes or atherosclerosis, they lose that spring. The top number climbs and the bottom number falls.
The same Mayo Clinic answer notes that many older adults have both a high systolic and a low diastolic, and that this wide gap, called high pulse pressure, is linked to stroke risk. Our post on pulse pressure explains how to work out the gap from your own readings.
Medicines for high blood pressure can lower the bottom number too. If you take them and your diastolic reads low, don't change, skip or stop anything on your own. Whether your treatment is right is your prescriber's decision.
Could the reading be wrong?
Sometimes a low diastolic is a setup problem. The American Heart Association's scientific statement on measuring blood pressure lists errors that push readings in both directions, and a few push them down.
A cuff that's too large for your arm tends to under-read. So does an arm held above heart level, for example resting on a high armrest or a pile of cushions. The statement also explains that most home monitors are oscillometric: they calculate both numbers from cuff pulsations with a built-in formula, so good technique matters.
Before you read anything into a low bottom number, check your cuff size and arm position, then measure again.
When should a low diastolic worry you?
Seek medical help immediately if a low reading comes with chest pain, shortness of breath, fainting, confusion, cold and clammy skin, or a weak, fast pulse. Those can be signs of shock, which is an emergency. Don't stay home re-measuring.
Book a regular appointment if your diastolic keeps reading under 60 and you notice dizziness, tiredness, or unsteadiness, or if your top number is high while the bottom is low. The advice from Mayo Clinic for a chronically low diastolic is to work with your doctor on the risk factors you can change, such as high blood pressure, smoking, cholesterol, diabetes and weight.
If you feel fine and it's a long-standing pattern, mention it at your next checkup.
How to check whether the low number holds
Use the routine from the AHA statement for a clean picture:
- Sit with your back supported, feet flat, and your arm resting at heart height.
- Rest quietly for five minutes.
- Take two readings one minute apart.
- Repeat morning and evening for seven days.
That's 2 readings × 2 sessions × 7 days = 28 readings. Average them and look at the bottom number. A single 57 in a week of 64s means little.
A week of 56s is a pattern worth sharing. Note how you felt each time.
Tracking your bottom number with BPlus
A low diastolic only makes sense next to your usual readings and your top number. BPlus is a logging app that keeps both in one place. Enter systolic, diastolic and pulse by hand, or scan your own monitor's display with the camera, and the time, date and arm are stamped automatically. Add a note such as "lightheaded after standing" to any reading.
The app charts your readings over time, sorts each one into the standard color-coded blood pressure categories, and exports a PDF or CSV report to take to your doctor. Daily reminders help you keep the morning and evening routine.
Your data stays on your device, works offline, and needs no account. BPlus is a wellness and logging tool, not a medical device. It doesn't measure blood pressure, diagnose low diastolic pressure or tell you what to do about it, and it's no substitute for professional care.
Mini-FAQ
Is a diastolic of 55 dangerous? Often not, on its own. Some people read in the 50s and feel fine. It's worth a doctor's visit if it comes with dizziness, fatigue or falls, if your top number is high at the same time, or if it's a drop from your usual level. With chest pain, fainting or breathlessness, seek medical help immediately.
Is low diastolic pressure common in older adults? Yes. As arteries stiffen with age, the bottom number tends to fall while the top number rises. Many older patients have a high systolic with a low diastolic. That combination is worth tracking and discussing with a doctor, because the wide gap carries its own risk.
Can my blood pressure pills make my diastolic too low? They can lower it, and only your prescriber can decide whether that matters for you. Never skip, stop or adjust a dose based on home readings. Log the low readings with times and symptoms, and contact your doctor, sooner if you feel faint or dizzy.
Can dehydration lower the bottom number? Yes. Dehydration lowers blood pressure overall, so the diastolic can dip along with the systolic. If a low reading follows a hot day, illness or little fluid, note that in your log and recheck once you've had enough to drink. If your readings stay low, or you feel dizzy or faint, tell your doctor.
Sources
- NHLBI: Low Blood Pressure
- Mayo Clinic News Network: Severe hypotension or stiff arteries may cause extremely low diastolic blood pressure
- McEvoy et al., Diastolic Blood Pressure, Subclinical Myocardial Damage, and Cardiac Events (JACC, 2016)
- American Heart Association: Measurement of Blood Pressure in Humans (Scientific Statement)
Medical disclaimer. BPlus is a wellness and informational tool that helps you record, organize and understand your blood pressure readings. It is not a medical device and does not diagnose, treat, cure or prevent any disease. BPlus does not measure blood pressure on its own. Always consult a qualified healthcare professional. Readings are not a substitute for a clinically validated blood pressure monitor.
