A blood pressure of 115/57 is partially good news: the top number (systolic) sits comfortably in the normal range, but the bottom number (diastolic) dips below a threshold that can signal a problem, especially for older adults. Whether this reading is something to celebrate or something to watch depends largely on your age, how you feel, and whether the pattern persists over time.
Where 115/57 Falls on the Chart
Both the American Heart Association and the American College of Cardiology define normal blood pressure as a systolic reading below 120 and a diastolic reading below 80. By that standard, 115/57 technically qualifies as normal because neither number crosses into the elevated or hypertension categories. The 2025 AHA/ACC guidelines maintain these same cutoffs.
But “below 80” covers a wide range, and guidelines don’t set a formal floor for how low is too low. That’s where the diastolic number in this reading gets more interesting. Researchers have defined a specific condition called isolated diastolic hypotension: a diastolic pressure below 60 combined with a normal systolic pressure above 100. At 115/57, this reading fits that definition exactly.
Why the Bottom Number Matters
Your diastolic pressure reflects the force in your arteries between heartbeats, when your heart is refilling with blood. This is also the moment when your coronary arteries receive most of their own blood supply. When diastolic pressure drops too low, the heart muscle itself may not get enough oxygen-rich blood. Over time, this low-level oxygen shortage can weaken the heart, a process cardiologists call ischemia.
Research from the Framingham Heart Study found that people with a diastolic pressure below 70 had significantly higher rates of cardiovascular events compared to those in the 70 to 89 range. The risk was especially pronounced when the gap between the top and bottom numbers (called pulse pressure) was wide. With a reading of 115/57, your pulse pressure is 58, which falls below the 68-point threshold where risk climbed most sharply in that study. That’s reassuring, but a diastolic of 57 still sits in the territory researchers flagged as potentially concerning.
A study highlighted by the University of Alabama at Birmingham found that older adults with isolated diastolic hypotension were at increased risk for developing new-onset heart failure. The lead researchers noted that once diastolic pressure drops below 60, many older people experience tiredness, dizziness, and frequent falls.
Age Changes the Picture Significantly
For a healthy, physically active person in their 20s or 30s, a diastolic reading of 57 is often completely benign. Younger people and athletes frequently run lower blood pressure numbers without any symptoms or health consequences. Their arteries are elastic, their hearts pump efficiently, and a low reading simply reflects cardiovascular fitness.
The calculus shifts after about age 50, and especially after 60. As arteries stiffen with age, systolic pressure tends to rise while diastolic pressure can actually fall. This creates a wider pulse pressure that strains the cardiovascular system in a different way. For someone over 60, a diastolic reading of 57 deserves closer attention, particularly if it’s a consistent finding rather than a one-time measurement. Research from the Framingham data showed that from age 60 onward, the gap between systolic and diastolic pressure becomes a stronger predictor of cardiovascular risk than either number alone.
Symptoms to Pay Attention To
A blood pressure reading only tells part of the story. How you feel at 115/57 matters just as much as the numbers themselves. Common symptoms of low diastolic pressure include:
- Dizziness or lightheadedness, particularly when standing up quickly
- Fatigue that doesn’t improve with rest
- Blurred or fading vision
- Trouble concentrating
- Fainting or near-fainting episodes
A drop of just 20 mmHg from your usual pressure can be enough to trigger dizziness or fainting. So if your diastolic normally runs in the mid-60s and has recently fallen to the mid-50s, that shift alone could produce symptoms even though the number might look acceptable on paper. If you’re experiencing none of these symptoms and feel fine in your daily life, a single reading of 115/57 is far less likely to indicate a problem.
What Can Push Diastolic Pressure Down
Several common factors can lower your diastolic reading. Dehydration is one of the most frequent culprits, and simply not drinking enough water on a hot day or after exercise can produce a temporarily low reading. Certain medications, especially those prescribed for high blood pressure, heart conditions, or depression, can lower diastolic pressure as a side effect. If you recently started or adjusted a medication and noticed your bottom number dropping, that connection is worth discussing with your prescriber.
Other contributors include prolonged bed rest, nutritional deficiencies (particularly low levels of B12, folate, or iron), and some heart valve conditions. Pregnancy also commonly lowers blood pressure, especially during the first and second trimesters, before it returns closer to baseline later on.
What to Do With This Reading
If you’re young, feel well, and got this reading once at a pharmacy kiosk or home monitor, there’s little reason for concern. A single blood pressure measurement is a snapshot, not a diagnosis. Blood pressure fluctuates throughout the day based on activity, stress, hydration, and even posture.
If you’re over 50, or if you’ve noticed a pattern of diastolic readings below 60, it’s worth tracking your numbers over a week or two at different times of day. Write down each reading along with the time and what you were doing. This log gives a much clearer picture than any single measurement. Consistently low diastolic readings paired with symptoms like fatigue, dizziness, or difficulty concentrating are a clear signal to bring those numbers to a medical appointment.
For people already taking blood pressure medication, a diastolic of 57 may indicate that your current dose is pulling the bottom number lower than intended. Adjusting treatment to lower systolic pressure without over-suppressing diastolic pressure is a common balancing act, and your provider can fine-tune the approach based on your full pattern of readings.